To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,an...To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning instrument.Based on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were analyzed.The failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane porosity.The damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle number.In order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further established.The results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.展开更多
The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory e...The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.展开更多
Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness...Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness of reservoir stimulation. Temporary plugging and diverting fracturing(TPDF) is considered to be a potential uniform-stimulation method for creating multiple fractures simultaneously in the oilfield. However, the multi-fracture propagation morphology during TPDF is not clear now. The purpose of this study is to quantitatively investigate the multi-fracture propagation morphology during TPDF through true tri-axial fracturing experiments and CT scanning. Critical parameters such as fracture spacing, number of perforation clusters, the viscosity of fracturing fluid, and the in-situ stress have been investigated. The fracture geometry before and after diversion have been quantitively analyzed based on the two-dimensional CT slices and three-dimensional reconstruction method. The main conclusions are as follows:(1) When injecting the high viscosity fluid or perforating at the location with low in-situ stress, multiple hydraulic fractures would simultaneously propagate. Otherwise, only one hydraulic fracture was created during the initial fracturing stage(IFS) for most tests.(2) The perforation cluster effectiveness(PCE) has increased from 26.62% during the IFS to 88.86% after using diverters.(3) The diverted fracture volume has no apparent correlation with the pressure peak and peak frequency during the diversion fracturing stage(DFS) but is positively correlated with water-work.(4) Four types of plugging behavior in shale could be controlled by adjusting the diverter recipe and diverter injection time, and the plugging behavior includes plugging the natural fracture in the wellbore, plugging the previous hydraulic fractures, plugging the fracture tip and plugging the bedding.展开更多
A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance(NMR)and CT scanning.The microscopic production mechanism of tight/shale ...A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance(NMR)and CT scanning.The microscopic production mechanism of tight/shale oil in pore throat by dynamic imbibition and the influencing factors on the development effect of dynamic imbibition were analyzed.The dynamic seepage process of fracking-soaking-backflow-production integration was simulated,which reveals the dynamic production characteristics at different development stages and their contribution to enhancing oil recovery(EOR).The seepage of tight/shale reservoirs can be divided into three stages:strong displacement and weak imbibition as oil produced rapidly by displacement from macropores and fractures,weak displacement and strong imbibition as oil produced slowly by reverse imbibition from small pores,and weak displacement and weak imbibition at dynamic equilibrium.The greater displacement pressure results in the higher displacement recovery and the lower imbibition recovery.However,if the displacement pressure is too high,the injected water is easy to break through the front and reduce the recovery degree.The higher the permeability,the greater the imbibition and displacement recovery,the shorter the time of imbibition balance,and the higher the final recovery.The fractures can effectively increase the imbibition contact area between matrix and water,reduce the oil-water seepage resistance,promote the oil-water displacement between matrix and fracture,and improve the oil displacement rate and recovery of the matrix.The soaking after fracturing is beneficial to the imbibition replacement and energy storage of the fluid;also,the effective use of the carrying of the backflow fluid and the displacement in the mining stage is the key to enhancing oil recovery.展开更多
Permafrost is an important part of the cryosphere,playing an integral role in the hydrologic cycle,ecology,and influencing human activity.Melting of ground ice can drastically change landscapes and associated thaw sub...Permafrost is an important part of the cryosphere,playing an integral role in the hydrologic cycle,ecology,and influencing human activity.Melting of ground ice can drastically change landscapes and associated thaw subsidence may induce instability of infrastructure.The terrain conditions on the Qinghai-Tibet Plateau are complex,and the spatial distribution of ground ice is highly variable,so knowledge of its abundance and variability is required for impact assessments relating to the degradation of permafrost.This study examined 55 permafrost samples from warm,ice-rich permafrost region in Beiluhe Basin,Qinghai-Tibet Plateau.The samples were examined using Computed Tomography scanning,and the ice content and cryostructure were determined.The results indicated that:1)variation in volumetric ice content was considerable(0%-70%),with a mean value of 17%;2)seven cryostructures were identified,including crustal,vein,lenticular,ataxitic,reticulate and layered cryostructure;3)volumetric ice content varied by cryostructure,with the highest associated with layered and ataxitic cryostructures.Volumetric ice contents were lowest for samples with pore and lenticular cryostructures.This work provides detailed ground ice content and will be helpful for assessing thaw subsidence and infrastructure stability on Qinghai-Tibet Plateau.展开更多
In order to understand the mechanism of air flooding shale oil, an online physical simulation method for enhanced shale oil recovery by air injection was established by integrating CT scanning and nuclear magnetic res...In order to understand the mechanism of air flooding shale oil, an online physical simulation method for enhanced shale oil recovery by air injection was established by integrating CT scanning and nuclear magnetic resonance(NMR). The development effect of shale oil by air flooding under different depletion pressures, the micro-production characteristics of pore throats with different sizes and the mechanism of shale oil recovery by air flooding were analyzed. The effects of air oxygen content, permeability, gas injection pressure, and fractures on the air flooding effect in shale and crude oil production in pores with different sizes were analyzed. The recovery of shale oil can be greatly improved by injecting air into the depleted shale reservoir, but the oil displacement efficiency and the production degree of different levels of pore throats vary with the injection timing. The higher the air oxygen content and the stronger the low-temperature oxidation, the higher the production degree of pores with different sizes and the higher the shale oil recovery. The higher the permeability and the better the pore throat connectivity, the stronger the fluid flow capacity and the higher the shale oil recovery. As the injection pressure increases, the lower limit of the production degree of pore throats decreases, but gas channeling may occur to cause a premature breakthrough;as a result, the recovery increases and then decreases. Fractures can effectively increase the contact area between gas and crude oil, and increase the air sweep coefficient and matrix oil drainage area by supplying oil to fractures through the matrix, which means that a proper fracturing before air injection can help to improve the oil displacement effect under a reasonable production pressure difference.展开更多
Soil-rock mixture(SRM),as a type of extremely heterogeneous geomaterial,is very common in nature and engineering.The fracture and damage of SRM often induce severe geological disasters.Hence,it is important to analyze...Soil-rock mixture(SRM),as a type of extremely heterogeneous geomaterial,is very common in nature and engineering.The fracture and damage of SRM often induce severe geological disasters.Hence,it is important to analyze the fracture evolution process of this material.In the present research,real-time computed tomography(CT)scanning was conducted on SRM and pure soil samples under uniaxial compressive experiments to investigate the influence of rocks on fracture evolution in SRM.The initiation of cracks,the original values of,and variations in,average density and heterogeneity in the soil matrix,the crack width evolution during loading,and the final failure modes were all studied.Cracks with a width greater than 0.1 mm will not arise until over 90%of ultimate stress is reached.In general,in SRM,areas where the initial average density of the soil matrix is smaller and the initial heterogeneity is greater,are much easier to crack,but the results for pure soil show the opposite effect.According to fracturing conditions shown in CT slices,fracturing and non-fracturing areas in the soil matrix were investigated.The average density of the soil matrix decreases in all areas under loading,except non-fracturing areas in SRM.For the whole sample,the increase in heterogeneity in the soil matrix of SRM is greater than that of pure soil;but for the fracturing areas,this increase in pure soil is greater.Besides,the average and standard deviations of crack width both follow logarithmic distributions with high correlation coefficients.展开更多
Internal erosion is one of the important factors causing geological disasters.The microstructure of soil can change with seepage erosion,resulting in changes in the hydraulic and mechanical properties of the soil.The ...Internal erosion is one of the important factors causing geological disasters.The microstructure of soil can change with seepage erosion,resulting in changes in the hydraulic and mechanical properties of the soil.The evolution of seepage erosion is investigated with X-ray computed tomography(CT)in this study.The change in macropore structure characteristics during the seepage erosion test is quantified and the influence of seepage erosion on soil deformation is analyzed.Moreover,a pore network model(PNM)is established for the specimens and the evolution of the connected pore size characteristics is assessed.The results show that the macropore structure is significantly affected by seepage erosion,especially in terms of the porosity and pore geometry characteristics.The changes in macropore structure characteristics are most obvious in the lower part of the specimen.The influence of seepage erosion on the pore size distribution(PSD)and soil deformation is heterogeneous and closely dependent on the spatial location of the soil.Moreover,seepage erosion enhances macropore connectivity and has a directional impact on macropore orientation.These findings can provide a reference for the theoretical modeling and numerical simulation of the seepage erosion and improve the understanding of the seepage erosion evolution in engineering practice.展开更多
Objective:To study the correlation between CT dynamic enhanced scanning parameters and serum tumor markers before and after radiofrequency ablation in patients with lung cancer.Methods:60 patients with advanced non-sm...Objective:To study the correlation between CT dynamic enhanced scanning parameters and serum tumor markers before and after radiofrequency ablation in patients with lung cancer.Methods:60 patients with advanced non-small cell lung cancer who were treated in this hospital between January 2015 and January 2017 were divided into control group(n=30)and observation group(n=30)by random number table method.Control group received conventional intravenous chemotherapy,and observation group received intravenous chemotherapy combined with radiofrequency ablation.The differences in CT dynamic enhanced scanning parameter levels and serum tumor marker contents were compared between the two groups of patients before and after treatment.Pearson test was used to evaluate the correlation between CT dynamic enhanced scanning parameters and serum tumor marker contents in patients with advanced non-small cell lung cancer.Results:Before treatment,the differences in CT dynamic enhanced scanning parameter levels,non-organ-specific tumor marker contents and vascular tumor marker contents were not statistically significant between the two groups of patients(P>0.05).After treatment,CT dynamic enhanced scanning parameters PH and perfusion value levels of observation group were lower than those of control group(P<0.05);serum non-organ specific tumor markers CA125,CA153,CEA and CYFRA21-1 contents of observation group were lower than those of control group;serum vascular tumor markers VEGF,Ang-2,HIF-1 and MMP-9 contents were lower than those of control group(P<0.05).Pearson test showed that CT dynamic enhanced scanning parameters PH and perfusion value levels in patients with non-small cell lung cancer were positively correlated with serum non-organ specific tumor marker and vascular tumor marker contents.Conclusion:Adjuvant radiofrequency ablation can significantly reduce the tumor malignancy of patients with advanced non-small cell lung cancer.展开更多
According to the World Health Organization(WHO),Brain Tumors(BrT)have a high rate of mortality across the world.The mortality rate,however,decreases with early diagnosis.Brain images,Computed Tomography(CT)scans,Magne...According to the World Health Organization(WHO),Brain Tumors(BrT)have a high rate of mortality across the world.The mortality rate,however,decreases with early diagnosis.Brain images,Computed Tomography(CT)scans,Magnetic Resonance Imaging scans(MRIs),segmentation,analysis,and evaluation make up the critical tools and steps used to diagnose brain cancer in its early stages.For physicians,diagnosis can be challenging and time-consuming,especially for those with little expertise.As technology advances,Artificial Intelligence(AI)has been used in various domains as a diagnostic tool and offers promising outcomes.Deep-learning techniques are especially useful and have achieved exquisite results.This study proposes a new Computer-Aided Diagnosis(CAD)system to recognize and distinguish between tumors and non-tumor tissues using a newly developed middleware to integrate two deep-learning technologies to segment brain MRI scans and classify any discovered tumors.The segmentation mechanism is used to determine the shape,area,diameter,and outline of any tumors,while the classification mechanism categorizes the type of cancer as slow-growing or aggressive.The main goal is to diagnose tumors early and to support the work of physicians.The proposed system integrates a Convolutional Neural Network(CNN),VGG-19,and Long Short-Term Memory Networks(LSTMs).A middleware framework is developed to perform the integration process and allow the system to collect the required data for the classification of tumors.Numerous experiments have been conducted on different five datasets to evaluate the presented system.These experiments reveal that the system achieves 97.98%average accuracy when the segmentation and classification functions were utilized,demonstrating that the proposed system is a powerful and valuable method to diagnose BrT early using MRI images.In addition,the system can be deployed in medical facilities to support and assist physicians to provide an early diagnosis to save patients’lives and avoid the high cost of treatments.展开更多
In recent days,Deep Learning(DL)techniques have become an emerging transformation in the field of machine learning,artificial intelligence,computer vision,and so on.Subsequently,researchers and industries have been hi...In recent days,Deep Learning(DL)techniques have become an emerging transformation in the field of machine learning,artificial intelligence,computer vision,and so on.Subsequently,researchers and industries have been highly endorsed in the medical field,predicting and controlling diverse diseases at specific intervals.Liver tumor prediction is a vital chore in analyzing and treating liver diseases.This paper proposes a novel approach for predicting liver tumors using Convolutional Neural Networks(CNN)and a depth-based variant search algorithm with advanced attention mechanisms(CNN-DS-AM).The proposed work aims to improve accuracy and robustness in diagnosing and treating liver diseases.The anticipated model is assessed on a Computed Tomography(CT)scan dataset containing both benign and malignant liver tumors.The proposed approach achieved high accuracy in predicting liver tumors,outperforming other state-of-the-art methods.Additionally,advanced attention mechanisms were incorporated into the CNN model to enable the identification and highlighting of regions of the CT scans most relevant to predicting liver tumors.The results suggest that incorporating attention mechanisms and a depth-based variant search algorithm into the CNN model is a promising approach for improving the accuracy and robustness of liver tumor prediction.It can assist radiologists in their diagnosis and treatment planning.The proposed system achieved a high accuracy of 95.5%in predicting liver tumors,outperforming other state-of-the-art methods.展开更多
One of the main obstacles hindering the exploitation of high-temperature and high-pressure oil and gas is the sealing integrity of the cement sheath.Analyzing the microstructure of the cement sheath is therefore an im...One of the main obstacles hindering the exploitation of high-temperature and high-pressure oil and gas is the sealing integrity of the cement sheath.Analyzing the microstructure of the cement sheath is therefore an important task.In this study,the microstructure of the cement sheath is determined using a CT scanner under different temperature and pressure conditions.The results suggest that the major cause of micro-cracks in the cement is the increase in the casing pressure.When the micro-cracks accumulate to a certain extent,the overall structure of the cement sheath is weakened,resulting in gas channeling,which poses a direct threat to the safe production of oil and gas.A change in the casing temperature has a limited effect on the microstructure of the cement sheath.展开更多
Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wa...Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wave at the national social insurance fund (NSIF) hospital were screened with both COVID-19 with lung CT scan and a PCR test. Univariate analysis was performed for sample description and multivariate analysis to assess the correlation between positive results for the PCR and other parameters. We estimated the optimum threshold of sensitivity/specificity, and area under curve using the empirical method and package. Results: A total of 62 suspected COVID-19 cases were recorded, predominantly males (Sex Ratio = 2.2) with a median age of 58.5 (IQR = 19.7). Among our 62 patients, 29 (46.8%) were confirmed COVID-19 cases with positive PCR results. All the patients had a thorax CT scan with a median impairment of 40% (IQR = 20%). The optimum threshold estimate for CT scan for COVID-19 infection diagnosis was 60% (95% CI = 25% - 80%). Overall, the sensitivity and specificity estimates were 0.30 (95% CI = 0.15 - 0.49) and 0.87 (95% CI = 0.70 - 0.96), respectively, leading to an Area Under Curve (AUC) estimate of 0.59 (95% CI = 0.46, 0.71). Conclusion: In this setting, lung CT scan was neither sensitive nor specific to predict COVID-19 disease.展开更多
Pore network structure of ore body is a diffusion channel of leaching agent solution that exerts a significant influence on seepage.The ore body structure,pore distribution,pore and throat size,and pore network charac...Pore network structure of ore body is a diffusion channel of leaching agent solution that exerts a significant influence on seepage.The ore body structure,pore distribution,pore and throat size,and pore network characteristics of topsoil,weathered,and semiweathered layers of ionic rare earth ore in southern Jiangxi Province were explored in this study.The effect of leaching operation on the pore structure was investigated,and main factors affecting the seepage were analyzed.Results showed that the semiweathered layer presents a dense structure and a small number of unconnected pores.Pores of topsoil and weathered layers are mainly long and narrow column openings with some planar fractures.Even pore distribution and large size span were observed.Compared with the weathered layer,the topsoil layer demonstrates larger voids,smaller average pore volume and equivalent radius,and fewer coordination throats;however,the average equivalent radius of the throat in the topsoil layer is larger and largescale channels exist through ore body vertically.Hence,permeability of the topsoil layer is significantly higher than that of the weathered layer.Colloidal clay minerals migrate easily and the occurrence of silting in the small porosity blocks the throat and significantly decreases the permeability of the ore body in the leaching process.The equivalent radius of the throat is the key to the seepage.Reducing the migration of fine particles is an effective measure to protect the throat and shorten the leaching period.展开更多
This article focuses on the process of rock creep damage and micro-damage evolution properties of gray green mudstone under impacting disturbance load conditions for the first time using the real time computerized tom...This article focuses on the process of rock creep damage and micro-damage evolution properties of gray green mudstone under impacting disturbance load conditions for the first time using the real time computerized tomography (CT) testing technique. The results indicate that axial load comes into limit strength neighborhood, rock micro-crack links into larger crack, creep rate increases in a short time, larger plastic deformation happens; this is called disturbance accelerating creep stage. When rock is within limit strength neighborhood, there occurs creep micro-damage under smaller disturbance load. When disturbance load is larger, rock directly enters into disturbance accelerating creep stage, failure occurs instantaneously. On the basis of experimental research, the CT scanning method was used to describe the creep micro-damage of soft rock, also helpful in the prediction of roadways' service life and evaluation of geotechnical engineering stability.展开更多
Gas-bearing sediments are widely distributed in five continents all over the world.Most of the gases exist in the soil skeleton in the form of discrete large bubbles.The existence of gas-phase may increase or decrease...Gas-bearing sediments are widely distributed in five continents all over the world.Most of the gases exist in the soil skeleton in the form of discrete large bubbles.The existence of gas-phase may increase or decrease the strength of the soil skeleton.So far,bubbles’structural morphology and evolution characteristics in soil skeleton lack research,and the influence of different gas reservoir pressures on bubbles are still unclear.The micro characteristics of bubbles in the same sediment sample were studied using an industrial CT scanning test system to solve these problems.Using the image processing software,the micro variation characteristics of gas-bearing sediments in gas reservoir pressure change are obtained.The results show that the number and volume of bubbles in different equivalent radius ranges will change regularly under different gas reservoir pressure.With the increase of gas reservoir pressure,the number and volume of tiny bubbles decrease.In contrast,the number and volume of large bubbles increase,and the gas content in different positions increases and occupies a dominant position,driving the reduction of pore water and soil skeleton movement.展开更多
Microscopic seepage characteristics are critical for the evaluation of tight sandstone reservoirs.In this study,a digital core approach integrating microscopic seepage simulation and CT scanning was developed to chara...Microscopic seepage characteristics are critical for the evaluation of tight sandstone reservoirs.In this study,a digital core approach integrating microscopic seepage simulation and CT scanning was developed to characterize microscopic seepage and fracture effectiveness(the ratio of micro-fractures that contributes to fluid flow)of tight sandstones.Numerical simulations were carried out for characterizations of tight sandstones.The results show that the axial permeability of the investigated cylindrical tight sandstone from Junggar Basin in China is 0.460μm~2,while the radial permeability is 0.3723μm~2,and the axial and radial effective fracture ratios are 0.4387 and 0.4806,respectively,indicating that cracks are not fully developed and the connectivity between micro-cracks is poor.Directional permeability that is difficult to measure by laboratory experiments can be obtained readily using the proposed method in this paper.The results provide important information for improving the exploration and development of tight sandstone reservoirs.展开更多
The principle of PCNL is the extraction through a nephrostomy channel of kidney stones which are defined as the presence of crystalline concretions in the kidneys. Objectives: The objective of this work was to study t...The principle of PCNL is the extraction through a nephrostomy channel of kidney stones which are defined as the presence of crystalline concretions in the kidneys. Objectives: The objective of this work was to study the epidemiological, clinical and paraclinical aspects of patients with renal lithiasis treated by PCNL and on the other hand the different technical aspects of PCNL. Materials and Methods: This was a retrospective descriptive study, conducted in the urology department of HOGIP, covering the period from January 2015 to January 2019. We studied the demographic and clinical aspects of patients presenting renal lithiasis;we also studied the technical aspects and treatment outcomes. Statistical significance was set for α = 0.05. Results: Our series covered 82 PCNLs performed during the study period. The average age was 45.95 years, the age group [40 - 49 years] was more affected. Our study involved 44 men and 38 women, a sex ratio of 1.15. At the clinic, atypical lumbar pain was more frequent in 45.83% of cases. On URO-CT, the calculations were located more at the pyelic level (31.2%) and lower caliceal (27.2%). The size of stones measured between 15 and 20 mm in 30.52%. The stone density was between 500 and 1000 HU in 47.54% of cases. Intraoperatively, the patients were placed in lateral decubitus in 41.46% of cases. Only one access to the kidney was necessary in 87.8% of cases. The lithoclast was used in 65.85% of cases. The overall success rate (stone free) in our series was 96%. The majority of cases, 41.44%, drainage were done by natural means (totally tubeless). The average duration was 92 minutes. The complications encountered in our experience concerned 10 cases, a rate of 12.19%. Conclusion: Urinary lithiasis is more and more frequent in our regions. The development of Endo-urology offers several therapeutic options. Thus, PCNL occupies an important place in the management of kidney stones.展开更多
Rocks in underground works usually experience rather complex stress disturbance.For this,their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions.The eff...Rocks in underground works usually experience rather complex stress disturbance.For this,their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions.The effects of stress disturbances on rock geomechanical behaviors under fatigue loading conditions and triaxial unloading conditions have been reported in previous studies.However,little is known about the dependence of the unloading rate on fatigue loading and confining stress unloading(FL-CSU)conditions that influence rock failure.In this paper,we aimed at investigating the fracture behaviors of marble under FL-CSU conditions using the post-test X-ray computed tomography(CT)scanning technique and the GCTS RTR 2000 rock mechanics system.Results show that damage accumulation at the fatigue stage can influence the final fracture behaviors of marble.The stored elastic energy for rock samples under FL-CSU tests is relatively larger compared to those under conventional triaxial tests,and the dissipated energy used to drive damage evolution and crack propagation is larger for FL-CSU tests.In FL-CSU tests,as the unloading rate increases,the dissipated energy grows and elastic energy reduces.CT scanning after the test reveals the impacts of the unloading rate on the crack pattern and a fracture degree index is therein defined in this context to represent the crack dimension.It shows that the crack pattern after FL-CSU tests depends on the unloading rate,and the fracture degree is in agreement with the analysis of both the energy dissipation and the amount of energy released.The effect of unloading rate on fracture evolution characteristics of marble is revealed by a series of FL-CSU tests.展开更多
基金supported by the National Natural Science Foundation of China(No.52178354).
文摘To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning instrument.Based on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were analyzed.The failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane porosity.The damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle number.In order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further established.The results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277150,41977219)Henan Provincial Science and Technology Research Project(Grant No.222102320271).
文摘The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.
基金the National Natural Science Foundation of China fund (Project number: 52174045 and No. 52104011)Research Foundation of China University of Petroleum-Beijing at Karamay (No. XQZX20210001)PetroChina Innovation Foundation (2020D50070207)。
文摘Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness of reservoir stimulation. Temporary plugging and diverting fracturing(TPDF) is considered to be a potential uniform-stimulation method for creating multiple fractures simultaneously in the oilfield. However, the multi-fracture propagation morphology during TPDF is not clear now. The purpose of this study is to quantitatively investigate the multi-fracture propagation morphology during TPDF through true tri-axial fracturing experiments and CT scanning. Critical parameters such as fracture spacing, number of perforation clusters, the viscosity of fracturing fluid, and the in-situ stress have been investigated. The fracture geometry before and after diversion have been quantitively analyzed based on the two-dimensional CT slices and three-dimensional reconstruction method. The main conclusions are as follows:(1) When injecting the high viscosity fluid or perforating at the location with low in-situ stress, multiple hydraulic fractures would simultaneously propagate. Otherwise, only one hydraulic fracture was created during the initial fracturing stage(IFS) for most tests.(2) The perforation cluster effectiveness(PCE) has increased from 26.62% during the IFS to 88.86% after using diverters.(3) The diverted fracture volume has no apparent correlation with the pressure peak and peak frequency during the diversion fracturing stage(DFS) but is positively correlated with water-work.(4) Four types of plugging behavior in shale could be controlled by adjusting the diverter recipe and diverter injection time, and the plugging behavior includes plugging the natural fracture in the wellbore, plugging the previous hydraulic fractures, plugging the fracture tip and plugging the bedding.
基金Supported by the PetroChina Science and Technology Major Project(2021-117)PetroChina CCUS Major Science and Technology Project(2021ZZ01-03)。
文摘A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance(NMR)and CT scanning.The microscopic production mechanism of tight/shale oil in pore throat by dynamic imbibition and the influencing factors on the development effect of dynamic imbibition were analyzed.The dynamic seepage process of fracking-soaking-backflow-production integration was simulated,which reveals the dynamic production characteristics at different development stages and their contribution to enhancing oil recovery(EOR).The seepage of tight/shale reservoirs can be divided into three stages:strong displacement and weak imbibition as oil produced rapidly by displacement from macropores and fractures,weak displacement and strong imbibition as oil produced slowly by reverse imbibition from small pores,and weak displacement and weak imbibition at dynamic equilibrium.The greater displacement pressure results in the higher displacement recovery and the lower imbibition recovery.However,if the displacement pressure is too high,the injected water is easy to break through the front and reduce the recovery degree.The higher the permeability,the greater the imbibition and displacement recovery,the shorter the time of imbibition balance,and the higher the final recovery.The fractures can effectively increase the imbibition contact area between matrix and water,reduce the oil-water seepage resistance,promote the oil-water displacement between matrix and fracture,and improve the oil displacement rate and recovery of the matrix.The soaking after fracturing is beneficial to the imbibition replacement and energy storage of the fluid;also,the effective use of the carrying of the backflow fluid and the displacement in the mining stage is the key to enhancing oil recovery.
基金supported by the National Key Research and Development of China(2017YFA0603101)the National Natural Science Foundation of China(grant 41971089)。
文摘Permafrost is an important part of the cryosphere,playing an integral role in the hydrologic cycle,ecology,and influencing human activity.Melting of ground ice can drastically change landscapes and associated thaw subsidence may induce instability of infrastructure.The terrain conditions on the Qinghai-Tibet Plateau are complex,and the spatial distribution of ground ice is highly variable,so knowledge of its abundance and variability is required for impact assessments relating to the degradation of permafrost.This study examined 55 permafrost samples from warm,ice-rich permafrost region in Beiluhe Basin,Qinghai-Tibet Plateau.The samples were examined using Computed Tomography scanning,and the ice content and cryostructure were determined.The results indicated that:1)variation in volumetric ice content was considerable(0%-70%),with a mean value of 17%;2)seven cryostructures were identified,including crustal,vein,lenticular,ataxitic,reticulate and layered cryostructure;3)volumetric ice content varied by cryostructure,with the highest associated with layered and ataxitic cryostructures.Volumetric ice contents were lowest for samples with pore and lenticular cryostructures.This work provides detailed ground ice content and will be helpful for assessing thaw subsidence and infrastructure stability on Qinghai-Tibet Plateau.
基金Supported by the PetroChina Major Scientific and Technological Research Project (2021DJ1102)PetroChina Science and Technology Major Project (2022kt1001)。
文摘In order to understand the mechanism of air flooding shale oil, an online physical simulation method for enhanced shale oil recovery by air injection was established by integrating CT scanning and nuclear magnetic resonance(NMR). The development effect of shale oil by air flooding under different depletion pressures, the micro-production characteristics of pore throats with different sizes and the mechanism of shale oil recovery by air flooding were analyzed. The effects of air oxygen content, permeability, gas injection pressure, and fractures on the air flooding effect in shale and crude oil production in pores with different sizes were analyzed. The recovery of shale oil can be greatly improved by injecting air into the depleted shale reservoir, but the oil displacement efficiency and the production degree of different levels of pore throats vary with the injection timing. The higher the air oxygen content and the stronger the low-temperature oxidation, the higher the production degree of pores with different sizes and the higher the shale oil recovery. The higher the permeability and the better the pore throat connectivity, the stronger the fluid flow capacity and the higher the shale oil recovery. As the injection pressure increases, the lower limit of the production degree of pore throats decreases, but gas channeling may occur to cause a premature breakthrough;as a result, the recovery increases and then decreases. Fractures can effectively increase the contact area between gas and crude oil, and increase the air sweep coefficient and matrix oil drainage area by supplying oil to fractures through the matrix, which means that a proper fracturing before air injection can help to improve the oil displacement effect under a reasonable production pressure difference.
基金the National Natural Science Foundation of China(Grant Nos.42090023,51734009 and 42002279)the Science Foundation of Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences(Grant No.KLSG201708)。
文摘Soil-rock mixture(SRM),as a type of extremely heterogeneous geomaterial,is very common in nature and engineering.The fracture and damage of SRM often induce severe geological disasters.Hence,it is important to analyze the fracture evolution process of this material.In the present research,real-time computed tomography(CT)scanning was conducted on SRM and pure soil samples under uniaxial compressive experiments to investigate the influence of rocks on fracture evolution in SRM.The initiation of cracks,the original values of,and variations in,average density and heterogeneity in the soil matrix,the crack width evolution during loading,and the final failure modes were all studied.Cracks with a width greater than 0.1 mm will not arise until over 90%of ultimate stress is reached.In general,in SRM,areas where the initial average density of the soil matrix is smaller and the initial heterogeneity is greater,are much easier to crack,but the results for pure soil show the opposite effect.According to fracturing conditions shown in CT slices,fracturing and non-fracturing areas in the soil matrix were investigated.The average density of the soil matrix decreases in all areas under loading,except non-fracturing areas in SRM.For the whole sample,the increase in heterogeneity in the soil matrix of SRM is greater than that of pure soil;but for the fracturing areas,this increase in pure soil is greater.Besides,the average and standard deviations of crack width both follow logarithmic distributions with high correlation coefficients.
基金the National Natural Science Foundation of China(No.41972297)the Natural Science Foundation of Hebei Province(No.D2021202002).
文摘Internal erosion is one of the important factors causing geological disasters.The microstructure of soil can change with seepage erosion,resulting in changes in the hydraulic and mechanical properties of the soil.The evolution of seepage erosion is investigated with X-ray computed tomography(CT)in this study.The change in macropore structure characteristics during the seepage erosion test is quantified and the influence of seepage erosion on soil deformation is analyzed.Moreover,a pore network model(PNM)is established for the specimens and the evolution of the connected pore size characteristics is assessed.The results show that the macropore structure is significantly affected by seepage erosion,especially in terms of the porosity and pore geometry characteristics.The changes in macropore structure characteristics are most obvious in the lower part of the specimen.The influence of seepage erosion on the pore size distribution(PSD)and soil deformation is heterogeneous and closely dependent on the spatial location of the soil.Moreover,seepage erosion enhances macropore connectivity and has a directional impact on macropore orientation.These findings can provide a reference for the theoretical modeling and numerical simulation of the seepage erosion and improve the understanding of the seepage erosion evolution in engineering practice.
基金Health and Family Planning Commission of Zigong(No.2017wZCS09)
文摘Objective:To study the correlation between CT dynamic enhanced scanning parameters and serum tumor markers before and after radiofrequency ablation in patients with lung cancer.Methods:60 patients with advanced non-small cell lung cancer who were treated in this hospital between January 2015 and January 2017 were divided into control group(n=30)and observation group(n=30)by random number table method.Control group received conventional intravenous chemotherapy,and observation group received intravenous chemotherapy combined with radiofrequency ablation.The differences in CT dynamic enhanced scanning parameter levels and serum tumor marker contents were compared between the two groups of patients before and after treatment.Pearson test was used to evaluate the correlation between CT dynamic enhanced scanning parameters and serum tumor marker contents in patients with advanced non-small cell lung cancer.Results:Before treatment,the differences in CT dynamic enhanced scanning parameter levels,non-organ-specific tumor marker contents and vascular tumor marker contents were not statistically significant between the two groups of patients(P>0.05).After treatment,CT dynamic enhanced scanning parameters PH and perfusion value levels of observation group were lower than those of control group(P<0.05);serum non-organ specific tumor markers CA125,CA153,CEA and CYFRA21-1 contents of observation group were lower than those of control group;serum vascular tumor markers VEGF,Ang-2,HIF-1 and MMP-9 contents were lower than those of control group(P<0.05).Pearson test showed that CT dynamic enhanced scanning parameters PH and perfusion value levels in patients with non-small cell lung cancer were positively correlated with serum non-organ specific tumor marker and vascular tumor marker contents.Conclusion:Adjuvant radiofrequency ablation can significantly reduce the tumor malignancy of patients with advanced non-small cell lung cancer.
文摘According to the World Health Organization(WHO),Brain Tumors(BrT)have a high rate of mortality across the world.The mortality rate,however,decreases with early diagnosis.Brain images,Computed Tomography(CT)scans,Magnetic Resonance Imaging scans(MRIs),segmentation,analysis,and evaluation make up the critical tools and steps used to diagnose brain cancer in its early stages.For physicians,diagnosis can be challenging and time-consuming,especially for those with little expertise.As technology advances,Artificial Intelligence(AI)has been used in various domains as a diagnostic tool and offers promising outcomes.Deep-learning techniques are especially useful and have achieved exquisite results.This study proposes a new Computer-Aided Diagnosis(CAD)system to recognize and distinguish between tumors and non-tumor tissues using a newly developed middleware to integrate two deep-learning technologies to segment brain MRI scans and classify any discovered tumors.The segmentation mechanism is used to determine the shape,area,diameter,and outline of any tumors,while the classification mechanism categorizes the type of cancer as slow-growing or aggressive.The main goal is to diagnose tumors early and to support the work of physicians.The proposed system integrates a Convolutional Neural Network(CNN),VGG-19,and Long Short-Term Memory Networks(LSTMs).A middleware framework is developed to perform the integration process and allow the system to collect the required data for the classification of tumors.Numerous experiments have been conducted on different five datasets to evaluate the presented system.These experiments reveal that the system achieves 97.98%average accuracy when the segmentation and classification functions were utilized,demonstrating that the proposed system is a powerful and valuable method to diagnose BrT early using MRI images.In addition,the system can be deployed in medical facilities to support and assist physicians to provide an early diagnosis to save patients’lives and avoid the high cost of treatments.
文摘In recent days,Deep Learning(DL)techniques have become an emerging transformation in the field of machine learning,artificial intelligence,computer vision,and so on.Subsequently,researchers and industries have been highly endorsed in the medical field,predicting and controlling diverse diseases at specific intervals.Liver tumor prediction is a vital chore in analyzing and treating liver diseases.This paper proposes a novel approach for predicting liver tumors using Convolutional Neural Networks(CNN)and a depth-based variant search algorithm with advanced attention mechanisms(CNN-DS-AM).The proposed work aims to improve accuracy and robustness in diagnosing and treating liver diseases.The anticipated model is assessed on a Computed Tomography(CT)scan dataset containing both benign and malignant liver tumors.The proposed approach achieved high accuracy in predicting liver tumors,outperforming other state-of-the-art methods.Additionally,advanced attention mechanisms were incorporated into the CNN model to enable the identification and highlighting of regions of the CT scans most relevant to predicting liver tumors.The results suggest that incorporating attention mechanisms and a depth-based variant search algorithm into the CNN model is a promising approach for improving the accuracy and robustness of liver tumor prediction.It can assist radiologists in their diagnosis and treatment planning.The proposed system achieved a high accuracy of 95.5%in predicting liver tumors,outperforming other state-of-the-art methods.
基金the research project from“Study of Risk assessment and Countermeasures of Well Drilling and Completion under Ultra-High Temperature and High Pressure”and“Research on Development Feasibility of LS25-1 Gas Field”(Grant Nos.YXKY-ZX-09-2021,2020FS-08).
文摘One of the main obstacles hindering the exploitation of high-temperature and high-pressure oil and gas is the sealing integrity of the cement sheath.Analyzing the microstructure of the cement sheath is therefore an important task.In this study,the microstructure of the cement sheath is determined using a CT scanner under different temperature and pressure conditions.The results suggest that the major cause of micro-cracks in the cement is the increase in the casing pressure.When the micro-cracks accumulate to a certain extent,the overall structure of the cement sheath is weakened,resulting in gas channeling,which poses a direct threat to the safe production of oil and gas.A change in the casing temperature has a limited effect on the microstructure of the cement sheath.
文摘Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wave at the national social insurance fund (NSIF) hospital were screened with both COVID-19 with lung CT scan and a PCR test. Univariate analysis was performed for sample description and multivariate analysis to assess the correlation between positive results for the PCR and other parameters. We estimated the optimum threshold of sensitivity/specificity, and area under curve using the empirical method and package. Results: A total of 62 suspected COVID-19 cases were recorded, predominantly males (Sex Ratio = 2.2) with a median age of 58.5 (IQR = 19.7). Among our 62 patients, 29 (46.8%) were confirmed COVID-19 cases with positive PCR results. All the patients had a thorax CT scan with a median impairment of 40% (IQR = 20%). The optimum threshold estimate for CT scan for COVID-19 infection diagnosis was 60% (95% CI = 25% - 80%). Overall, the sensitivity and specificity estimates were 0.30 (95% CI = 0.15 - 0.49) and 0.87 (95% CI = 0.70 - 0.96), respectively, leading to an Area Under Curve (AUC) estimate of 0.59 (95% CI = 0.46, 0.71). Conclusion: In this setting, lung CT scan was neither sensitive nor specific to predict COVID-19 disease.
基金supported by the National Natural Science Foundation of China(Nos.51774153,92062110)National Key Research and Development Program of China(No.2021YFC2901702)。
文摘Pore network structure of ore body is a diffusion channel of leaching agent solution that exerts a significant influence on seepage.The ore body structure,pore distribution,pore and throat size,and pore network characteristics of topsoil,weathered,and semiweathered layers of ionic rare earth ore in southern Jiangxi Province were explored in this study.The effect of leaching operation on the pore structure was investigated,and main factors affecting the seepage were analyzed.Results showed that the semiweathered layer presents a dense structure and a small number of unconnected pores.Pores of topsoil and weathered layers are mainly long and narrow column openings with some planar fractures.Even pore distribution and large size span were observed.Compared with the weathered layer,the topsoil layer demonstrates larger voids,smaller average pore volume and equivalent radius,and fewer coordination throats;however,the average equivalent radius of the throat in the topsoil layer is larger and largescale channels exist through ore body vertically.Hence,permeability of the topsoil layer is significantly higher than that of the weathered layer.Colloidal clay minerals migrate easily and the occurrence of silting in the small porosity blocks the throat and significantly decreases the permeability of the ore body in the leaching process.The equivalent radius of the throat is the key to the seepage.Reducing the migration of fine particles is an effective measure to protect the throat and shorten the leaching period.
基金the National Natural ScienceFoundation of China (No. 50474029).
文摘This article focuses on the process of rock creep damage and micro-damage evolution properties of gray green mudstone under impacting disturbance load conditions for the first time using the real time computerized tomography (CT) testing technique. The results indicate that axial load comes into limit strength neighborhood, rock micro-crack links into larger crack, creep rate increases in a short time, larger plastic deformation happens; this is called disturbance accelerating creep stage. When rock is within limit strength neighborhood, there occurs creep micro-damage under smaller disturbance load. When disturbance load is larger, rock directly enters into disturbance accelerating creep stage, failure occurs instantaneously. On the basis of experimental research, the CT scanning method was used to describe the creep micro-damage of soft rock, also helpful in the prediction of roadways' service life and evaluation of geotechnical engineering stability.
基金The Shandong Joint Funds of National Natural Science Foundation of China under contract No.U2006213the Fundamental Research Funds for the Central Universities under contract No.201962011the Grant of Laboratory for Marine Geology,Pilot National Laboratory for Marine Science and Technology(Qingdao)under contract No.MGQNLM-KF201804。
文摘Gas-bearing sediments are widely distributed in five continents all over the world.Most of the gases exist in the soil skeleton in the form of discrete large bubbles.The existence of gas-phase may increase or decrease the strength of the soil skeleton.So far,bubbles’structural morphology and evolution characteristics in soil skeleton lack research,and the influence of different gas reservoir pressures on bubbles are still unclear.The micro characteristics of bubbles in the same sediment sample were studied using an industrial CT scanning test system to solve these problems.Using the image processing software,the micro variation characteristics of gas-bearing sediments in gas reservoir pressure change are obtained.The results show that the number and volume of bubbles in different equivalent radius ranges will change regularly under different gas reservoir pressure.With the increase of gas reservoir pressure,the number and volume of tiny bubbles decrease.In contrast,the number and volume of large bubbles increase,and the gas content in different positions increases and occupies a dominant position,driving the reduction of pore water and soil skeleton movement.
基金financially supported by the National Natural Science Foundation of China(Grant No.41972138)the Technology Major Project of China(Grant No.ZD2019-183007,2016ZX05002-002)。
文摘Microscopic seepage characteristics are critical for the evaluation of tight sandstone reservoirs.In this study,a digital core approach integrating microscopic seepage simulation and CT scanning was developed to characterize microscopic seepage and fracture effectiveness(the ratio of micro-fractures that contributes to fluid flow)of tight sandstones.Numerical simulations were carried out for characterizations of tight sandstones.The results show that the axial permeability of the investigated cylindrical tight sandstone from Junggar Basin in China is 0.460μm~2,while the radial permeability is 0.3723μm~2,and the axial and radial effective fracture ratios are 0.4387 and 0.4806,respectively,indicating that cracks are not fully developed and the connectivity between micro-cracks is poor.Directional permeability that is difficult to measure by laboratory experiments can be obtained readily using the proposed method in this paper.The results provide important information for improving the exploration and development of tight sandstone reservoirs.
文摘The principle of PCNL is the extraction through a nephrostomy channel of kidney stones which are defined as the presence of crystalline concretions in the kidneys. Objectives: The objective of this work was to study the epidemiological, clinical and paraclinical aspects of patients with renal lithiasis treated by PCNL and on the other hand the different technical aspects of PCNL. Materials and Methods: This was a retrospective descriptive study, conducted in the urology department of HOGIP, covering the period from January 2015 to January 2019. We studied the demographic and clinical aspects of patients presenting renal lithiasis;we also studied the technical aspects and treatment outcomes. Statistical significance was set for α = 0.05. Results: Our series covered 82 PCNLs performed during the study period. The average age was 45.95 years, the age group [40 - 49 years] was more affected. Our study involved 44 men and 38 women, a sex ratio of 1.15. At the clinic, atypical lumbar pain was more frequent in 45.83% of cases. On URO-CT, the calculations were located more at the pyelic level (31.2%) and lower caliceal (27.2%). The size of stones measured between 15 and 20 mm in 30.52%. The stone density was between 500 and 1000 HU in 47.54% of cases. Intraoperatively, the patients were placed in lateral decubitus in 41.46% of cases. Only one access to the kidney was necessary in 87.8% of cases. The lithoclast was used in 65.85% of cases. The overall success rate (stone free) in our series was 96%. The majority of cases, 41.44%, drainage were done by natural means (totally tubeless). The average duration was 92 minutes. The complications encountered in our experience concerned 10 cases, a rate of 12.19%. Conclusion: Urinary lithiasis is more and more frequent in our regions. The development of Endo-urology offers several therapeutic options. Thus, PCNL occupies an important place in the management of kidney stones.
基金The authors would like to thank the editors and the anonymous reviewers for their helpful and constructive comments.This study was supported by National Key Technologies Research&Development Program(Grant No.2018YFC0808402)State Key Laboratory for GeoMechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK1824)the Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-20-004A2).
文摘Rocks in underground works usually experience rather complex stress disturbance.For this,their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions.The effects of stress disturbances on rock geomechanical behaviors under fatigue loading conditions and triaxial unloading conditions have been reported in previous studies.However,little is known about the dependence of the unloading rate on fatigue loading and confining stress unloading(FL-CSU)conditions that influence rock failure.In this paper,we aimed at investigating the fracture behaviors of marble under FL-CSU conditions using the post-test X-ray computed tomography(CT)scanning technique and the GCTS RTR 2000 rock mechanics system.Results show that damage accumulation at the fatigue stage can influence the final fracture behaviors of marble.The stored elastic energy for rock samples under FL-CSU tests is relatively larger compared to those under conventional triaxial tests,and the dissipated energy used to drive damage evolution and crack propagation is larger for FL-CSU tests.In FL-CSU tests,as the unloading rate increases,the dissipated energy grows and elastic energy reduces.CT scanning after the test reveals the impacts of the unloading rate on the crack pattern and a fracture degree index is therein defined in this context to represent the crack dimension.It shows that the crack pattern after FL-CSU tests depends on the unloading rate,and the fracture degree is in agreement with the analysis of both the energy dissipation and the amount of energy released.The effect of unloading rate on fracture evolution characteristics of marble is revealed by a series of FL-CSU tests.