Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the s...Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(i.e.cohesion and internal friction angle)when they are supported by cemented backfilling.In this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure criterion.Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be determined.The value of s3max predicted using the proposed method is generally less than 3 MPa.Within this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb theory.The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,i.e.the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided.The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method.The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations.The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.展开更多
Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already w...Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already widespread worldwide and requires careful stewardship.In this study,we review the presence of potentially toxic elements(PTEs)in PG and describe their associations with soil properties,anthropogenic activities,and surrounding organisms.Then,we review different ex-/in-situ solutions for promoting the sustainable management of PG,with an emphasis on in-situ cemented paste backfill,which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG.However,concerns related to the PTEs'retention capacity and long-term effectiveness limit the implementation of this strategy.Furthermore,given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO_(2) emissions,the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China's Carbon Neutrality Economy.Therefore,we discuss the ways by which we can integrate innovative strategies,including supplementary cementitious materials,alternative binder solutions,CO_(2) mineralization,CO_(2) curing,and optimization of the supply chain for the profitability and sustainability of PG remediation.However,to maximize the co-benefits in environmental,social,and economic,future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.展开更多
The fractured surrounding rocks of roadways pose major challenges to safe mining.Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks.The aim of ...The fractured surrounding rocks of roadways pose major challenges to safe mining.Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks.The aim of this study is to develop highly efficient composite ultrafine cement(CUC)grouts to reinforce the roadway in fractured surrounding rocks.The materials used are ultrafine cement(UC),ultrafine fly ash(UF),ultrafine slag(US),and additives(superplasticizer[SUP],aluminate ultrafine expansion agent[AUA],gypsum,and retarder).The fluidity,bleeding,shrinkage,setting time,chemical composition,microstructure,degree of hydration,and mechanical property of grouting materials were evaluated in this study.Also,a suitable and effective CUC grout mixture was used to reinforce the roadway in the fractured surrounding rock.The results have shown that the addition of UF and US reduces the plastic viscosity of CUC,and the best fluidity can be obtained by adding 40%UF and 10%US.Since UC and UF particles are small,the pozzolanic effect of UF promotes the hydration reaction,which is conductive to the stability of CUC grouts.In addition,fine particles of UC,UF,and US can effectively fill the pores,while the volumetric expansion of AUA and gypsum decreases the pores and thus affects the microstructure of the solidified grout.The compressive test results have shown that the addition of specific amounts of UF and US can ameliorate the mechanical properties of CUC grouts.Finally,the CUC22‐8 grout was used to reinforce the No.20322 belt roadway.The results of numerical simulation and field monitoring have indicated that grouting can efficaciously reinforce the surrounding rock of the roadway.In this research,high‐performance CUC grouts were developed for surrounding rock reinforcement of underground engineering by utilizing UC and some additives.展开更多
The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture ...The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%.展开更多
The substantial arsenic(As)content present in arsenic-containing bio-leaching residue(ABR)presents noteworthy environ-mental challenges attributable to its inherent instability and susceptibility to leaching.Given its...The substantial arsenic(As)content present in arsenic-containing bio-leaching residue(ABR)presents noteworthy environ-mental challenges attributable to its inherent instability and susceptibility to leaching.Given its elevated calcium sulfate content,ABR exhibits considerable promise for industrial applications.This study delved into the feasibility of utilizing ABR as a source of sulfates for producing super sulfated cement(SSC),offering an innovative binder for cemented paste backfill(CPB).Thermal treatment at varying temperatures of 150,350,600,and 800℃ was employed to modify ABR’s performance.The investigation encompassed the examination of phase transformations and alterations in the chemical composition of As within ABR.Subsequently,the hydration characteristics of SSC utilizing ABR,with or without thermal treatment,were studied,encompassing reaction kinetics,setting time,strength development,and microstructure.The findings revealed that thermal treatment changed the calcium sulfate structure in ABR,consequently impacting the resultant sample performance.Notably,calcination at 600℃ demonstrated optimal modification effects on both early and long-term strength attributes.This enhanced performance can be attributed to the augmented formation of reaction products and a densified micro-structure.Furthermore,the thermal treatment elicited modifications in the chemical As fractions within ABR,with limited impact on the As immobilization capacity of the prepared binders.展开更多
In order to better solve the problem of electromagnetic pollution in the civil building cement,to improve the absorption capacity of magnesium oxysulfide cement based materials,and to better use sulfur oxide magnesium...In order to better solve the problem of electromagnetic pollution in the civil building cement,to improve the absorption capacity of magnesium oxysulfide cement based materials,and to better use sulfur oxide magnesium cement foamed sheet for improvement of electromagnetic industry,this paper uses the excellent microwave absorbing properties of ferrite and the modified sulfur oxide magnesium cement foam board,and discusses the microwave absorbing performance,aiming at improving the electromagnetic pollution in daily life.The effects of ferrite and silicon carbide doping on microwave absorption properties of modified magnesium oxysulfate cement were studied.At the same time,the wave absorbing properties of the corresponding samples were detected by bow method,and the causes of the corresponding phenomena were analyzed by scanning electron microscopy (SEM).The results show that the lowest reflectance of the material is-17.9 dB at 34.1 GHz and the average reflectance of the whole band is-15.9 dB under the target frequency band of 26.5-40 GHz.Under the action of external magnetic field,the absorbing particles are affected by magnetization force,magnetic dipole and resistance coupling,and play the absorbing effect in the cement base solidified completely in the electromagnetic field environment.The lowest reflectance is-17.3dB at 36.4GHz and the average reflectance is-14.3dB for the whole band.展开更多
The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste matrix.In this study,the effects of shear-induced forces and proportio...The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste matrix.In this study,the effects of shear-induced forces and proportioning parameters on the microstructure of fresh CPB were studied.The size evolution and distribution of floc/agglomerate/particles of paste were monitored by focused beam reflection measuring(FBRM)technique,and the influencing factors of aggregation and breakage kinetics of CPB were discussed.The results indicate that influenced by both internal and external factors,the paste kinetics evolution covers the dynamic phase and the stable phase.Increasing the mass content or the cement-tailings ratio can accelerate aggregation kinetics,which is advantageous for the rise of average floc size.Besides,the admixture and high shear can improve breaking kinetics,which is beneficial to reduce the average floc size.The chord length resembles a normal distribution somewhat,with a peak value of approximate 20μm.The particle disaggregation con-stant(k_(2))is positively correlated with the agitation rate,and k_(2) is five orders of magnitude greater than the particle aggregation constant(k1).The kinetics model depicts the evolution law of particles over time quantitatively and provides a theoretical foundation for the micromechanics of complicated rheological behavior of paste.展开更多
It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the co...It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.展开更多
Minerals in Portland cement including tricalcium silicate(C_(3)S),β-dicalcium silicate(β-C_(2)S),tricalcium aluminate(C_(3)A),and tetracalcium ferroaluminate(C_(4)AF),show a significantly different activity and prod...Minerals in Portland cement including tricalcium silicate(C_(3)S),β-dicalcium silicate(β-C_(2)S),tricalcium aluminate(C_(3)A),and tetracalcium ferroaluminate(C_(4)AF),show a significantly different activity and product evolution for CO_(2)curing at various water-to-solid ratios.These pure minerals were synthesized and subject to CO_(2)curing in this study to make an in-depth understanding for the carbonation properties of cement-based materials.Results showed that the optimum water-to-solid ratios of C_(3)S,β-C_(2)S,C_(3)A and C_(4)AF were 0.25,0.15,0.30 and 0.40 for carbonation,corresponding to 2 h carbonation degree of 38.5%,38.5%,24.2%,and 21.9%,respectively.The produced calcite duringβ-C_(2)S carbonation decreased as the water-to-solid ratio increased,with an increase in content of metastable CaCO_(3)of vaterite and aragonite.The thermodynamic stability of CaCO_(3)produced during carbonation was C_(3)A>C_(4)AF>β-C_(2)S>C_(3)S.The carbonation degree of Portland cement was predicted based on the results of pure minerals and the composition of cement,and the error of predicted production of CaCO_(3)was only 1.1%,which provides a potential method to predict carbonation properties of systems with a complex mineral composition.展开更多
WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravi...WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.展开更多
To improve the brittleness characteristics of magnesium phosphate cement-based materials(MPC)and to promote its promotion and application in the field of structural reinforcement and repair,this study aimed to increas...To improve the brittleness characteristics of magnesium phosphate cement-based materials(MPC)and to promote its promotion and application in the field of structural reinforcement and repair,this study aimed to increase the toughness of MPC by adding jute fiber,explore the effects of different amounts of jute fiber on the working and mechanical properties of MPC,and prepare jute fiber reinforced magnesium phosphate cement-based materials(JFRMPC)to reinforce damaged beams.The improvement effect of beam performance before and after reinforcement was compared,and the strengthening and toughening mechanisms of jute fiber on MPC were explored through microscopic analysis.The experimental results show that,as the content of jute fiber(JF)increases,the fluidity and setting time of MPC decrease continuously;When the content of jute fiber is 0.8%,the compressive strength,flexural strength,and bonding strength of MPC at 28 days reach their maximum values,which are increased by 18.0%,20.5%,and 22.6%compared to those of M0,respectively.The beam strengthened with JFRMPC can withstand greater deformation,with a deflection of 2.3 times that of the unreinforced beam at failure.The strain of the steel bar is greatly reduced,and the initial crack and failure loads of the reinforced beam are increased by 192.1%and 16.1%,respectively,compared to those of the unreinforced beam.The JF added to the MPC matrix dissipates energy through tensile fracture and debonding pull-out,slowing down stress concentration and inhibiting the free development of cracks in the matrix,enabling JFRMPC to exhibit higher strength and better toughness.The JF does not cause the hydration of MPC to generate new compounds but reduces the amount of hydration products generated.展开更多
Understanding the mechanical properties and multiscale failure mechanism of frozen soft rock is an important prerequisite for the construction safety of tunnels,artificially frozen ground and other infrastructure in c...Understanding the mechanical properties and multiscale failure mechanism of frozen soft rock is an important prerequisite for the construction safety of tunnels,artificially frozen ground and other infrastructure in cold regions.In this study,the triaxial compression test are performed on mudstone in the weakly cemented soft rock strata in the mining area of western China,and the mechanical characteristics and failure mechanism of weakly cemented mudstone are systematically investigated under the combined action of freezing and loading.Furthermore,the quantitative relationship between the microstructural parameters and the macroscopic strength and deformation parameters is established based on fractal theory.Thus,the failure mechanism of frozen weakly cemented mudstone is revealed on both micro- and macro-scales.The results show that temperature and confining pressure significantly affects the elastic modulus and peak strength of weakly cemented mudstone.With decreasing temperature,the compressive strength increases,while the corresponding peak strain decreases gradually.On the deformation curve,the plastic deformation stage is shortened,and the brittle fracture feature at the post-peak stage is more prominent,and the elastic modulus correspondingly increases with decreasing temperature.Under low-temperature conditions,most of the weakly cemented mudstone undergoes microscopic shear failure along the main fracture surface.The micro-fracture morphology characteristics of weakly cemented mudstone under different temperatures are quantified via the fractal dimension,and an approximately exponential relationship can be obtained among the fractal dimension and the temperature,compressive strength and elastic modulus.展开更多
In this paper,the durability of cement mortar prepared with a recycled-concrete fine powder(RFP)was examined;including the analysis of a variety of aspects,such as the carbonization,sulfate attack and chloride ion ero...In this paper,the durability of cement mortar prepared with a recycled-concrete fine powder(RFP)was examined;including the analysis of a variety of aspects,such as the carbonization,sulfate attack and chloride ion erosion resistance.The results indicate that the influence of RFP on these three aspects is different.The carbonization depth after 30 days and the chloride diffusion coefficient of mortar containing 10%RFP decreased by 13.3%and 28.19%.With a further increase in the RFP content,interconnected pores formed between the RFP particles,leading to an acceleration of the penetration rate of CO_(2)and Cl^(−).When the RFP content was less than 50%,the corrosion resistance coefficient of the compressive strength of the mortar was 0.84-1.05 after 90 days of sulfate attack.But the expansion and cracking of the mortar was effectively alleviated due to decrease of the gypsum production.Scanning electron microscope(SEM)analysis has confirmed that 10%RFP contributes to the formation of a dense microstructure in the cement mortar.展开更多
Cement density monitoring plays a vital role in evaluating the quality of cementing projects,which is of great significance to the development of oil and gas.However,the presence of inhomogeneous cement distribution a...Cement density monitoring plays a vital role in evaluating the quality of cementing projects,which is of great significance to the development of oil and gas.However,the presence of inhomogeneous cement distribution and casing eccentricity in horizontal wells often complicates the accurate evaluation of cement azimuthal density.In this regard,this paper proposes an algorithm to calculate the cement azimuthal density in horizontal wells using a multi-detector gamma-ray detection system.The spatial dynamic response functions are simulated to obtain the influence of cement density on gamma-ray counts by the perturbation theory,and the contribution of cement density in six sectors to the gamma-ray recorded by different detectors is obtained by integrating the spatial dynamic response functions.Combined with the relationship between gamma-ray counts and cement density,a multi-parameter calculation equation system is established,and the regularized Newton iteration method is employed to invert casing eccentricity and cement azimuthal density.This approach ensures the stability of the inversion process while simultaneously achieving an accuracy of 0.05 g/cm^(3) for the cement azimuthal density.This accuracy level is ten times higher compared to density accuracy calculated using calibration equations.Overall,this algorithm enhances the accuracy of cement azimuthal density evaluation,provides valuable technical support for the monitoring of cement azimuthal density in the oil and gas industry.展开更多
The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.O...The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.展开更多
Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing challenge.The use of superabsorbent polymers(SAP)has gained significant attention as a possible way to i...Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing challenge.The use of superabsorbent polymers(SAP)has gained significant attention as a possible way to improve the performance of cement-based materials due to their unique water-absorption and retention properties.This study investigates the multifaceted impact of kaolin intercalation-modified superabsorbent polymers(K-SAP)on the properties of cement mortar.The results show that K-SAP significantly affects the cement mortar’s rheological behavior,with distinct phases of water absorption and release,leading to changes in workability over time.Furthermore,K-SAP alters the hydration kinetics,delaying the exothermic peak of hydration and subsequently modifying the heat release kinetics.Notably,K-SAP effectively maintains a higher internal relative humidity within the mortar,reducing the autogenous shrinkage behavior.Moreover,K-SAP can have a beneficial effect on pore structure and this can be ascribed to the internal curing effect of released water from K-SAP.展开更多
This research proposes a highly effective soft computing paradigm for estimating the compressive strength(CS)of metakaolin-contained cemented materials.The proposed approach is a combination of an enhanced grey wolf o...This research proposes a highly effective soft computing paradigm for estimating the compressive strength(CS)of metakaolin-contained cemented materials.The proposed approach is a combination of an enhanced grey wolf optimizer(EGWO)and an extreme learning machine(ELM).EGWO is an augmented form of the classic grey wolf optimizer(GWO).Compared to standard GWO,EGWO has a better hunting mechanism and produces an optimal performance.The EGWO was used to optimize the ELM structure and a hybrid model,ELM-EGWO,was built.To train and validate the proposed ELM-EGWO model,a sum of 361 experimental results featuring five influencing factors was collected.Based on sensitivity analysis,three distinct cases of influencing parameters were considered to investigate the effect of influencing factors on predictive precision.Experimental consequences show that the constructed ELM-EGWO achieved the most accurate precision in both training(RMSE=0.0959)and testing(RMSE=0.0912)phases.The outcomes of the ELM-EGWO are significantly superior to those of deep neural networks(DNN),k-nearest neighbors(KNN),long short-term memory(LSTM),and other hybrid ELMs constructed with GWO,particle swarm optimization(PSO),harris hawks optimization(HHO),salp swarm algorithm(SSA),marine predators algorithm(MPA),and colony predation algorithm(CPA).The overall results demonstrate that the newly suggested ELM-EGWO has the potential to estimate the CS of metakaolin-contained cemented materials with a high degree of precision and robustness.展开更多
The deep cement mixing(DCM)is used to improve the capacity and reduce the settlement of the soft ground by forming cemented clay columns.The investigation on the mechanical behaviour of the DCM samples is limited to e...The deep cement mixing(DCM)is used to improve the capacity and reduce the settlement of the soft ground by forming cemented clay columns.The investigation on the mechanical behaviour of the DCM samples is limited to either laboratory-prepared samples or in-situ samples under unconfined compression.In this study,a series of drained and undrained triaxial shearing tests was performed on the in-situ cored DCM samples with high cement content to assess their mechanical behaviours.It is found that the drainage condition affects significantly the stiffness,peak and residual strengths of the DCM samples,which is mainly due to the state of excess pore water pressure at different strain levels,i.e.being positive before the peak deviatoric stress and negative after the peak deviatoric stress,in the undrained tests.The slope of the failure envelope changes obviously with the confining pressures,being steeper at lower stress levels and flatter at higher stress levels.The strength parameters,effective cohesion and friction angle obtained from lower stress levels(c′0 andφ′0)are 400 kPa and 58°,respectively,which are deemed to be true for design in most DCM applications where the in-situ stress levels are normally at lower values of 50-200 kPa.Additionally,the computed tomography(CT)scanning system was adopted to visualize the internal structures of DCM samples.It is found that the clay pockets existing inside the DCM samples due to uneven mixing affect markedly their stress-strain behaviour,which is one of the main reasons for the high variability of the DCM samples.展开更多
BACKGROUND Percutaneous kyphoplasty(PKP)is a pivotal intervention for osteoporotic fractures,pathological vertebral compression fractures,and vertebral bone tumors.Despite its efficacy,the procedure presents challenge...BACKGROUND Percutaneous kyphoplasty(PKP)is a pivotal intervention for osteoporotic fractures,pathological vertebral compression fractures,and vertebral bone tumors.Despite its efficacy,the procedure presents challenges,notably complications arising from intradural cement leakage.Timely and accurate diagnosis,coupled with emergent intervention is imperative to improve patient prognosis.This case report illuminates the intricacies and potential complications associated with PKP,emphasizing the critical need for vigilant monitoring,prompt diagnosis,and immediate intervention to mitigate adverse outcomes.CASE SUMMARY A 58-year-old male patient,experiencing a T7 osteoporosis-related pathological compression fracture,underwent PKP at a local hospital.Two weeks postprocedure,the patient developed paraplegic and dysuric symptoms,necessitating emergency decompression surgery.Gradual improvement was achieved,marked by the restoration of muscle strength,sensation,and mobility.CONCLUSION PKP Intradural cement leakage following PKP is unusual and potentially fatal.Prompt imaging examinations,urgent evaluation,and the decompression surgery are essential,which help alleviate symptoms associated with spinal damage,markedly improving the overall prognosis.展开更多
BACKGROUND Although percutaneous vertebral augmentation(PVA)is a commonly used procedure for treating vertebral compression fracture(VCF),the risk of vertebral refracture should be considered.Chronic kidney disease-mi...BACKGROUND Although percutaneous vertebral augmentation(PVA)is a commonly used procedure for treating vertebral compression fracture(VCF),the risk of vertebral refracture should be considered.Chronic kidney disease-mineral and bone disorder(CKD-MBD)is a systemic disease of mineral and bone metabolism.It is associated with an increased risk of fracture.Few studies have reported the use of PVA in patients with CKD-MBD.We herein report a rare case wherein the cemented vertebra and the adjacent vertebra refractured simultaneously in a CKD-MBD patient after PVA.CASE SUMMARY A 74-year-old man suffered from low back pain after taking a fall about 3 wk ago.According to physical examination,imaging and laboratory findings,diagnoses of T12 VCF,CKD-MBD,and chronic kidney disease stage 5 were established.He then received percutaneous vertebroplasty at T12 vertebra.Fourteen weeks later,he presented with T12 and L1 vertebral refractures caused by lumbar sprain.Once again,he was given PVA which was optimized for the refractured vertebrae.Although the short-term postoperative effect was satisfactory,he reported chronic low back pain again at the 3-month follow-up.CONCLUSION It is necessary that patients with CKD-MBD who have received PVA are aware of the adverse effects of CKD-MBD.It may increase the risk of vertebral refracture.Furthermore,the PVA surgical technique needs to be optimized according to the condition of the patient.The medium-and long-term effects of PVA remain uncertain in patients with CKD-MBD.展开更多
基金Financial support for this work was provided by the General Program and Youth Fund Program of the National Natural Science Foundation of China(Grant Nos.42377175 and 42002292).
文摘Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(i.e.cohesion and internal friction angle)when they are supported by cemented backfilling.In this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure criterion.Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be determined.The value of s3max predicted using the proposed method is generally less than 3 MPa.Within this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb theory.The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,i.e.the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided.The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method.The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations.The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.
基金the National Natural Science Foundation of China(Nos.552104156,52074351,and 52004330)the National Natural Science Foundation of Hunan Province,China(No.2022JJ30714)the Science and Technology Innovation Program of Hunan Province,China(No.2021RC3125)。
文摘Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already widespread worldwide and requires careful stewardship.In this study,we review the presence of potentially toxic elements(PTEs)in PG and describe their associations with soil properties,anthropogenic activities,and surrounding organisms.Then,we review different ex-/in-situ solutions for promoting the sustainable management of PG,with an emphasis on in-situ cemented paste backfill,which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG.However,concerns related to the PTEs'retention capacity and long-term effectiveness limit the implementation of this strategy.Furthermore,given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO_(2) emissions,the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China's Carbon Neutrality Economy.Therefore,we discuss the ways by which we can integrate innovative strategies,including supplementary cementitious materials,alternative binder solutions,CO_(2) mineralization,CO_(2) curing,and optimization of the supply chain for the profitability and sustainability of PG remediation.However,to maximize the co-benefits in environmental,social,and economic,future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.
基金supported by the National Natural Science Foundation of China(NSFC)(grant No.52074169,No.51704280)the China Postdoctoral Science Foundation(No.2023M732109)the Opening Foundation of Shandong Key Laboratory of Civil Engineering Disaster Prevention and Mitigation(No.CDPM2021FK02).
文摘The fractured surrounding rocks of roadways pose major challenges to safe mining.Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks.The aim of this study is to develop highly efficient composite ultrafine cement(CUC)grouts to reinforce the roadway in fractured surrounding rocks.The materials used are ultrafine cement(UC),ultrafine fly ash(UF),ultrafine slag(US),and additives(superplasticizer[SUP],aluminate ultrafine expansion agent[AUA],gypsum,and retarder).The fluidity,bleeding,shrinkage,setting time,chemical composition,microstructure,degree of hydration,and mechanical property of grouting materials were evaluated in this study.Also,a suitable and effective CUC grout mixture was used to reinforce the roadway in the fractured surrounding rock.The results have shown that the addition of UF and US reduces the plastic viscosity of CUC,and the best fluidity can be obtained by adding 40%UF and 10%US.Since UC and UF particles are small,the pozzolanic effect of UF promotes the hydration reaction,which is conductive to the stability of CUC grouts.In addition,fine particles of UC,UF,and US can effectively fill the pores,while the volumetric expansion of AUA and gypsum decreases the pores and thus affects the microstructure of the solidified grout.The compressive test results have shown that the addition of specific amounts of UF and US can ameliorate the mechanical properties of CUC grouts.Finally,the CUC22‐8 grout was used to reinforce the No.20322 belt roadway.The results of numerical simulation and field monitoring have indicated that grouting can efficaciously reinforce the surrounding rock of the roadway.In this research,high‐performance CUC grouts were developed for surrounding rock reinforcement of underground engineering by utilizing UC and some additives.
基金the supports of project funded by China Postdoctoral Science Foundation(2023M743886)Project of Shale Gas Evaluation and Exploitation Key Laboratory of Sichuan Province(YSK2023004)youth project funded by Shaanxi Province Natural Science Basic Research Program(2024JC-YBQN-0522)。
文摘The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%.
基金supported from the National Natural Science Foundation of China(No.52304148)the Youth Project of Shanxi Basic Research Program,China(No.202203021212262).
文摘The substantial arsenic(As)content present in arsenic-containing bio-leaching residue(ABR)presents noteworthy environ-mental challenges attributable to its inherent instability and susceptibility to leaching.Given its elevated calcium sulfate content,ABR exhibits considerable promise for industrial applications.This study delved into the feasibility of utilizing ABR as a source of sulfates for producing super sulfated cement(SSC),offering an innovative binder for cemented paste backfill(CPB).Thermal treatment at varying temperatures of 150,350,600,and 800℃ was employed to modify ABR’s performance.The investigation encompassed the examination of phase transformations and alterations in the chemical composition of As within ABR.Subsequently,the hydration characteristics of SSC utilizing ABR,with or without thermal treatment,were studied,encompassing reaction kinetics,setting time,strength development,and microstructure.The findings revealed that thermal treatment changed the calcium sulfate structure in ABR,consequently impacting the resultant sample performance.Notably,calcination at 600℃ demonstrated optimal modification effects on both early and long-term strength attributes.This enhanced performance can be attributed to the augmented formation of reaction products and a densified micro-structure.Furthermore,the thermal treatment elicited modifications in the chemical As fractions within ABR,with limited impact on the As immobilization capacity of the prepared binders.
基金Funded by National Defense Basic Research Program Project。
文摘In order to better solve the problem of electromagnetic pollution in the civil building cement,to improve the absorption capacity of magnesium oxysulfide cement based materials,and to better use sulfur oxide magnesium cement foamed sheet for improvement of electromagnetic industry,this paper uses the excellent microwave absorbing properties of ferrite and the modified sulfur oxide magnesium cement foam board,and discusses the microwave absorbing performance,aiming at improving the electromagnetic pollution in daily life.The effects of ferrite and silicon carbide doping on microwave absorption properties of modified magnesium oxysulfate cement were studied.At the same time,the wave absorbing properties of the corresponding samples were detected by bow method,and the causes of the corresponding phenomena were analyzed by scanning electron microscopy (SEM).The results show that the lowest reflectance of the material is-17.9 dB at 34.1 GHz and the average reflectance of the whole band is-15.9 dB under the target frequency band of 26.5-40 GHz.Under the action of external magnetic field,the absorbing particles are affected by magnetization force,magnetic dipole and resistance coupling,and play the absorbing effect in the cement base solidified completely in the electromagnetic field environment.The lowest reflectance is-17.3dB at 36.4GHz and the average reflectance is-14.3dB for the whole band.
基金financially supported by the National Natural Science Foundation of China(No.52104129)the Shandong Provincial Major Science and Technology Innovation Project,China(No.2019SDZY05)+2 种基金the key Laboratory of Mine Ecological Effects and Systematic Restoration,Ministry of Natural Resources(No.MEER-2022-09)the Double First-class Construction Project in Henan Province,China(No.AQ20230735)the Doctoral Fund of Henan Polytechnic University(No.B2021-59).
文摘The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste matrix.In this study,the effects of shear-induced forces and proportioning parameters on the microstructure of fresh CPB were studied.The size evolution and distribution of floc/agglomerate/particles of paste were monitored by focused beam reflection measuring(FBRM)technique,and the influencing factors of aggregation and breakage kinetics of CPB were discussed.The results indicate that influenced by both internal and external factors,the paste kinetics evolution covers the dynamic phase and the stable phase.Increasing the mass content or the cement-tailings ratio can accelerate aggregation kinetics,which is advantageous for the rise of average floc size.Besides,the admixture and high shear can improve breaking kinetics,which is beneficial to reduce the average floc size.The chord length resembles a normal distribution somewhat,with a peak value of approximate 20μm.The particle disaggregation con-stant(k_(2))is positively correlated with the agitation rate,and k_(2) is five orders of magnitude greater than the particle aggregation constant(k1).The kinetics model depicts the evolution law of particles over time quantitatively and provides a theoretical foundation for the micromechanics of complicated rheological behavior of paste.
基金Funded by the National Natural Science Foundation of China(No.51802235)Hubei Science and Technology Innovation Talent Project,China(No.2023DJC087)。
文摘It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.
基金Funded by Hainan Provincial Natural Science Foundation of China(No.522QN279)State Key Laboratory of High Performance Civil Engineering Materials(No.2023CEM004)Natural Science Foundation of Jiangsu Province(No.BK20231088)。
文摘Minerals in Portland cement including tricalcium silicate(C_(3)S),β-dicalcium silicate(β-C_(2)S),tricalcium aluminate(C_(3)A),and tetracalcium ferroaluminate(C_(4)AF),show a significantly different activity and product evolution for CO_(2)curing at various water-to-solid ratios.These pure minerals were synthesized and subject to CO_(2)curing in this study to make an in-depth understanding for the carbonation properties of cement-based materials.Results showed that the optimum water-to-solid ratios of C_(3)S,β-C_(2)S,C_(3)A and C_(4)AF were 0.25,0.15,0.30 and 0.40 for carbonation,corresponding to 2 h carbonation degree of 38.5%,38.5%,24.2%,and 21.9%,respectively.The produced calcite duringβ-C_(2)S carbonation decreased as the water-to-solid ratio increased,with an increase in content of metastable CaCO_(3)of vaterite and aragonite.The thermodynamic stability of CaCO_(3)produced during carbonation was C_(3)A>C_(4)AF>β-C_(2)S>C_(3)S.The carbonation degree of Portland cement was predicted based on the results of pure minerals and the composition of cement,and the error of predicted production of CaCO_(3)was only 1.1%,which provides a potential method to predict carbonation properties of systems with a complex mineral composition.
基金Funded by the National Key Research and Development Plan of China(No.2017YFB0305900)。
文摘WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.
基金the Science and Technology Research Project of Chongqing Education Commission(Nos.KJZD-K201901201,KJZD-202101201)the Top-notch Young Talents in Chongqing(No.CQYC201905086)the Technology Innovation and Application Development Project in Wanzhou District,Chongqing(No.wzstc-2019031)。
文摘To improve the brittleness characteristics of magnesium phosphate cement-based materials(MPC)and to promote its promotion and application in the field of structural reinforcement and repair,this study aimed to increase the toughness of MPC by adding jute fiber,explore the effects of different amounts of jute fiber on the working and mechanical properties of MPC,and prepare jute fiber reinforced magnesium phosphate cement-based materials(JFRMPC)to reinforce damaged beams.The improvement effect of beam performance before and after reinforcement was compared,and the strengthening and toughening mechanisms of jute fiber on MPC were explored through microscopic analysis.The experimental results show that,as the content of jute fiber(JF)increases,the fluidity and setting time of MPC decrease continuously;When the content of jute fiber is 0.8%,the compressive strength,flexural strength,and bonding strength of MPC at 28 days reach their maximum values,which are increased by 18.0%,20.5%,and 22.6%compared to those of M0,respectively.The beam strengthened with JFRMPC can withstand greater deformation,with a deflection of 2.3 times that of the unreinforced beam at failure.The strain of the steel bar is greatly reduced,and the initial crack and failure loads of the reinforced beam are increased by 192.1%and 16.1%,respectively,compared to those of the unreinforced beam.The JF added to the MPC matrix dissipates energy through tensile fracture and debonding pull-out,slowing down stress concentration and inhibiting the free development of cracks in the matrix,enabling JFRMPC to exhibit higher strength and better toughness.The JF does not cause the hydration of MPC to generate new compounds but reduces the amount of hydration products generated.
基金funding support from Natural Science Foundation of Shandong Province(Grant No.ZR2021QE187).
文摘Understanding the mechanical properties and multiscale failure mechanism of frozen soft rock is an important prerequisite for the construction safety of tunnels,artificially frozen ground and other infrastructure in cold regions.In this study,the triaxial compression test are performed on mudstone in the weakly cemented soft rock strata in the mining area of western China,and the mechanical characteristics and failure mechanism of weakly cemented mudstone are systematically investigated under the combined action of freezing and loading.Furthermore,the quantitative relationship between the microstructural parameters and the macroscopic strength and deformation parameters is established based on fractal theory.Thus,the failure mechanism of frozen weakly cemented mudstone is revealed on both micro- and macro-scales.The results show that temperature and confining pressure significantly affects the elastic modulus and peak strength of weakly cemented mudstone.With decreasing temperature,the compressive strength increases,while the corresponding peak strain decreases gradually.On the deformation curve,the plastic deformation stage is shortened,and the brittle fracture feature at the post-peak stage is more prominent,and the elastic modulus correspondingly increases with decreasing temperature.Under low-temperature conditions,most of the weakly cemented mudstone undergoes microscopic shear failure along the main fracture surface.The micro-fracture morphology characteristics of weakly cemented mudstone under different temperatures are quantified via the fractal dimension,and an approximately exponential relationship can be obtained among the fractal dimension and the temperature,compressive strength and elastic modulus.
基金This work is supported by the Zhuhai Science and Technology Project(ZH22036203200015PWC)the Open Foundation of State Key Laboratory of Subtropical Building Science(2022ZB20).
文摘In this paper,the durability of cement mortar prepared with a recycled-concrete fine powder(RFP)was examined;including the analysis of a variety of aspects,such as the carbonization,sulfate attack and chloride ion erosion resistance.The results indicate that the influence of RFP on these three aspects is different.The carbonization depth after 30 days and the chloride diffusion coefficient of mortar containing 10%RFP decreased by 13.3%and 28.19%.With a further increase in the RFP content,interconnected pores formed between the RFP particles,leading to an acceleration of the penetration rate of CO_(2)and Cl^(−).When the RFP content was less than 50%,the corrosion resistance coefficient of the compressive strength of the mortar was 0.84-1.05 after 90 days of sulfate attack.But the expansion and cracking of the mortar was effectively alleviated due to decrease of the gypsum production.Scanning electron microscope(SEM)analysis has confirmed that 10%RFP contributes to the formation of a dense microstructure in the cement mortar.
基金The authors would like to acknowledge the support of the National Natural Science Foundation of China(41974127,42174147).References。
文摘Cement density monitoring plays a vital role in evaluating the quality of cementing projects,which is of great significance to the development of oil and gas.However,the presence of inhomogeneous cement distribution and casing eccentricity in horizontal wells often complicates the accurate evaluation of cement azimuthal density.In this regard,this paper proposes an algorithm to calculate the cement azimuthal density in horizontal wells using a multi-detector gamma-ray detection system.The spatial dynamic response functions are simulated to obtain the influence of cement density on gamma-ray counts by the perturbation theory,and the contribution of cement density in six sectors to the gamma-ray recorded by different detectors is obtained by integrating the spatial dynamic response functions.Combined with the relationship between gamma-ray counts and cement density,a multi-parameter calculation equation system is established,and the regularized Newton iteration method is employed to invert casing eccentricity and cement azimuthal density.This approach ensures the stability of the inversion process while simultaneously achieving an accuracy of 0.05 g/cm^(3) for the cement azimuthal density.This accuracy level is ten times higher compared to density accuracy calculated using calibration equations.Overall,this algorithm enhances the accuracy of cement azimuthal density evaluation,provides valuable technical support for the monitoring of cement azimuthal density in the oil and gas industry.
基金Funded by the Technology Innovation Leading Program of Shaanxi(No.2022QFY08-02)。
文摘The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.
基金the National Natural Science Foundation of China(52172017 and 51902095).
文摘Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing challenge.The use of superabsorbent polymers(SAP)has gained significant attention as a possible way to improve the performance of cement-based materials due to their unique water-absorption and retention properties.This study investigates the multifaceted impact of kaolin intercalation-modified superabsorbent polymers(K-SAP)on the properties of cement mortar.The results show that K-SAP significantly affects the cement mortar’s rheological behavior,with distinct phases of water absorption and release,leading to changes in workability over time.Furthermore,K-SAP alters the hydration kinetics,delaying the exothermic peak of hydration and subsequently modifying the heat release kinetics.Notably,K-SAP effectively maintains a higher internal relative humidity within the mortar,reducing the autogenous shrinkage behavior.Moreover,K-SAP can have a beneficial effect on pore structure and this can be ascribed to the internal curing effect of released water from K-SAP.
基金supported via funding from Prince Sattam Bin Abdulaziz University Project Number(PSAU/2023/R/1445).
文摘This research proposes a highly effective soft computing paradigm for estimating the compressive strength(CS)of metakaolin-contained cemented materials.The proposed approach is a combination of an enhanced grey wolf optimizer(EGWO)and an extreme learning machine(ELM).EGWO is an augmented form of the classic grey wolf optimizer(GWO).Compared to standard GWO,EGWO has a better hunting mechanism and produces an optimal performance.The EGWO was used to optimize the ELM structure and a hybrid model,ELM-EGWO,was built.To train and validate the proposed ELM-EGWO model,a sum of 361 experimental results featuring five influencing factors was collected.Based on sensitivity analysis,three distinct cases of influencing parameters were considered to investigate the effect of influencing factors on predictive precision.Experimental consequences show that the constructed ELM-EGWO achieved the most accurate precision in both training(RMSE=0.0959)and testing(RMSE=0.0912)phases.The outcomes of the ELM-EGWO are significantly superior to those of deep neural networks(DNN),k-nearest neighbors(KNN),long short-term memory(LSTM),and other hybrid ELMs constructed with GWO,particle swarm optimization(PSO),harris hawks optimization(HHO),salp swarm algorithm(SSA),marine predators algorithm(MPA),and colony predation algorithm(CPA).The overall results demonstrate that the newly suggested ELM-EGWO has the potential to estimate the CS of metakaolin-contained cemented materials with a high degree of precision and robustness.
基金funded by the Environment and Conservation Fund(Grant Nos.2020-170 and 2021-156)the National Natural Science Foundation of China(Grant No.42102327).
文摘The deep cement mixing(DCM)is used to improve the capacity and reduce the settlement of the soft ground by forming cemented clay columns.The investigation on the mechanical behaviour of the DCM samples is limited to either laboratory-prepared samples or in-situ samples under unconfined compression.In this study,a series of drained and undrained triaxial shearing tests was performed on the in-situ cored DCM samples with high cement content to assess their mechanical behaviours.It is found that the drainage condition affects significantly the stiffness,peak and residual strengths of the DCM samples,which is mainly due to the state of excess pore water pressure at different strain levels,i.e.being positive before the peak deviatoric stress and negative after the peak deviatoric stress,in the undrained tests.The slope of the failure envelope changes obviously with the confining pressures,being steeper at lower stress levels and flatter at higher stress levels.The strength parameters,effective cohesion and friction angle obtained from lower stress levels(c′0 andφ′0)are 400 kPa and 58°,respectively,which are deemed to be true for design in most DCM applications where the in-situ stress levels are normally at lower values of 50-200 kPa.Additionally,the computed tomography(CT)scanning system was adopted to visualize the internal structures of DCM samples.It is found that the clay pockets existing inside the DCM samples due to uneven mixing affect markedly their stress-strain behaviour,which is one of the main reasons for the high variability of the DCM samples.
文摘BACKGROUND Percutaneous kyphoplasty(PKP)is a pivotal intervention for osteoporotic fractures,pathological vertebral compression fractures,and vertebral bone tumors.Despite its efficacy,the procedure presents challenges,notably complications arising from intradural cement leakage.Timely and accurate diagnosis,coupled with emergent intervention is imperative to improve patient prognosis.This case report illuminates the intricacies and potential complications associated with PKP,emphasizing the critical need for vigilant monitoring,prompt diagnosis,and immediate intervention to mitigate adverse outcomes.CASE SUMMARY A 58-year-old male patient,experiencing a T7 osteoporosis-related pathological compression fracture,underwent PKP at a local hospital.Two weeks postprocedure,the patient developed paraplegic and dysuric symptoms,necessitating emergency decompression surgery.Gradual improvement was achieved,marked by the restoration of muscle strength,sensation,and mobility.CONCLUSION PKP Intradural cement leakage following PKP is unusual and potentially fatal.Prompt imaging examinations,urgent evaluation,and the decompression surgery are essential,which help alleviate symptoms associated with spinal damage,markedly improving the overall prognosis.
文摘BACKGROUND Although percutaneous vertebral augmentation(PVA)is a commonly used procedure for treating vertebral compression fracture(VCF),the risk of vertebral refracture should be considered.Chronic kidney disease-mineral and bone disorder(CKD-MBD)is a systemic disease of mineral and bone metabolism.It is associated with an increased risk of fracture.Few studies have reported the use of PVA in patients with CKD-MBD.We herein report a rare case wherein the cemented vertebra and the adjacent vertebra refractured simultaneously in a CKD-MBD patient after PVA.CASE SUMMARY A 74-year-old man suffered from low back pain after taking a fall about 3 wk ago.According to physical examination,imaging and laboratory findings,diagnoses of T12 VCF,CKD-MBD,and chronic kidney disease stage 5 were established.He then received percutaneous vertebroplasty at T12 vertebra.Fourteen weeks later,he presented with T12 and L1 vertebral refractures caused by lumbar sprain.Once again,he was given PVA which was optimized for the refractured vertebrae.Although the short-term postoperative effect was satisfactory,he reported chronic low back pain again at the 3-month follow-up.CONCLUSION It is necessary that patients with CKD-MBD who have received PVA are aware of the adverse effects of CKD-MBD.It may increase the risk of vertebral refracture.Furthermore,the PVA surgical technique needs to be optimized according to the condition of the patient.The medium-and long-term effects of PVA remain uncertain in patients with CKD-MBD.