Water-induced softening behavior of clay-rich sandstone in Lanzhou Water Supply Project,China

The strength of clay-rich sandstone decreases significantly when in contact with water due to softening effects.This scenario can pose a severe threat to the stability of water diversion tunnels during construction and operation periods.To address the issues related to water-induced softening in clay-rich sandstone zones in a water diversion tunnel of Lanzhou Water Supply Project,the microscopic and micromechanical variations of rocks due to increasing water content in two different zones i.e.zones A and B,were determined by various testing methods,such as X-ray diffraction(XRD),scanning electron microscopy(SEM),thin section microscopy,micro-indentation test,sonic velocity test,and slake durability test.The microscopic analysis confirms the presence of montmorillonite mineral which is the dominant problematic geomaterial in engineering application.The integrity and durability of clay-rich sandstone were determined with sonic velocity and slake durability tests to calibrate the results obtained by the micro-indentation test.It shows that the elastic modulus and hardness of clay-rich sandstone decrease with the increase of saturation time,up to 144 h,which is more significant and rapid during early stage of saturation.After 144 h of saturation,the elastic modulus decreases by 89% and 97%,and the hardness decreases by 89% and 99% for zones A and B sandstones,respectively.The results of slake durability and sonic velocity indicate that zone A sandsto ne remains 56.19% durability after 144 h of saturation,while zone B sandstone loses its durability merely after 72 h of saturation.The clay-rich sandstone starts to dissolve in water when the saturation time exceeds 144 h.The significant decreases in strength and durability of clay-rich sandstone due to water-induced softening are serious threats to tunnel stability.The improvements in the strength of surrounding rock mass by grouting and permeability by installation of drainage galleries can reduce the damage caused by water-induced softening.

Wave propagation across fluid-solid interfaces with LBM-LSM coupling schemes

Seismic wave propagation in fluid-solid coupled media is currently a popular topic. However, traditional wave equation-based simulation methods have to consider complex boundary conditions at the fluid-solid interface. To address this challenge, we propose a novel numerical scheme that integrates the lattice Boltzmann method(LBM) and lattice spring model(LSM). In this scheme, LBM simulates viscoacoustic wave propagation in the fluid area and LSM simulates elastic wave propagation in the solid area. We also introduce three different LBM-LSM coupling strategies, a standard bounce back scheme, a specular reflection scheme, and a hybrid scheme, to describe wave propagation across fluid-solid boundaries. To demonstrate the accuracy of these LBM-LSM coupling schemes, we simulate wave propagation in a two-layer model containing a fluid-solid interface. We place excitation sources in the fluid layer and the solid layer respectively, to observe the wave phenomena when seismic waves propagate to interface from different sides. The simulated results by LBM-LSM are compared with the reference wavefields obtained by the finite difference method(FDM) and the analytical solution(ANA).Our LBM-LSM coupling scheme was verified effective, as the relative errors between the LBM-LSM solutions and reference solutions were within an acceptable range, sometimes around 1.00%. The coupled LBM-LSM scheme is further used to model seismic wavefields across a more realistic rugged seabed,which reveals the potential applications of the coupled LBM-LSM scheme in marine seismic imaging techniques, such as reverse-time migration and full-waveform inversion. The method also has potential applications in simulating wave propagation in complex two-and multi-phase media.

Clogging caused by coupled grain migration and compaction effect during groundwater recharge for unconsolidated sandstone reservoir in groundwater-source heat pump

In unconsolidated sandstone reservoirs,presence of numerous movable grains and a complex grain size composition necessitates a clear understanding of the physical clogging process for effective groundwater recharge in groundwater-source heat pump systems.To investigate this,a series of seepage experiments was conducted under in situ stress conditions using unconsolidated sandstone samples with varying grain compositions.The clogging phenomenon arises from the combined effects of grain migration and compaction,wherein the migration of both original and secondary crushed fine-grain particles blocks the seepage channels.Notably,grain composition influences the migration and transport properties of the grains.For samples composed of smaller grains,the apparent permeability demonstrates a transition from stability to decrease.In contrast,samples with larger grains experience a skip at the stability stage and directly enter the decrease stage,with a minor exception of a slight increase observed.Furthermore,a unique failure mode characterized by diameter shrinkage in the upper part of the sample is observed due to the combined effects of grain migration and in situ stress-induced compaction.These testing results contribute to a better understanding of the clogging mechanism caused by the coupled effects of grain migration and compaction during groundwater recharge in unconsolidated sandstone reservoirs used in groundwater-source heat pump systems.

New possibility for PET plastic recycling by a tailored hydrolytic enzyme

Plastic waste puts a huge burden on the ecosystem due to the current lack of mature recycling technology.Poly(ethylene terephthalate)(PET)is one of the most produced plastics in the world.Enzymatic decomposition holds the promise of recovering monomers from PET plastic,and the monomers can be used to regenerate new PET products.However,there are still limitations in the activity and thermal stability of the existing PET hydrolases.The recent study by Lu et al.introduced a novel PET hydrolase via machine learning-aided engineering.The obtained PET hydrolase showed excellent activity and thermal stability in the hydrolysis of PET and is capable of directly degrading large amounts of postconsumer PET products.This approach provides an effective method for recycling PET waste and is expected to improve the current state of plastic pollution worldwide.

Upcycling municipal solid waste to sustainable hydrogen via two-stage gasification-reforming

As global municipal solid waste(MSW)quantities continue to escalate,serious socio-environmental challenges arise,necessitating innovative solutions.Waste-to-hydrogen(WTH)via two-stage gasification-reforming(TSGR)presents an emergent technology for MSW upcycling,offering to ease waste management burdens and bolster the burgeoning hydrogen economy.Despite early initiatives to advance TSGR technology,a cohesive and critical analysis of cutting-edge knowledge and strategies to enhance hydrogen production remains lacking.This review aggregates literature on MSW upcycling to hydrogen via TSGR,with a focus on optimizing process control and catalytic efficiency.It underscores technological avenues to augment hydrogen output,curtail catalyst costs,and refine system performance.Particularly,the review illuminates the potential for integrating chemical and calcium looping into TSGR processes,identifying opportunities,and pinpointing challenges.The review concludes with a summary of the current state of techno-economic analysis for this technology,presenting outstanding challenges and future research directions,with the ultimate goal of transitioning WTH from theoretical to practical application.

Positron Emission Tomography Lung Image Respiratory Motion Correcting with Equivariant Transformer

In addressing the challenge of motion artifacts in Positron Emission Tomography (PET) lung scans, our studyintroduces the Triple Equivariant Motion Transformer (TEMT), an innovative, unsupervised, deep-learningbasedframework for efficient respiratory motion correction in PET imaging. Unlike traditional techniques,which segment PET data into bins throughout a respiratory cycle and often face issues such as inefficiency andoveremphasis on certain artifacts, TEMT employs Convolutional Neural Networks (CNNs) for effective featureextraction and motion decomposition.TEMT’s unique approach involves transforming motion sequences into Liegroup domains to highlight fundamental motion patterns, coupled with employing competitive weighting forprecise target deformation field generation. Our empirical evaluations confirm TEMT’s superior performancein handling diverse PET lung datasets compared to existing image registration networks. Experimental resultsdemonstrate that TEMT achieved Dice indices of 91.40%, 85.41%, 79.78%, and 72.16% on simulated geometricphantom data, lung voxel phantom data, cardiopulmonary voxel phantom data, and clinical data, respectively. Tofacilitate further research and practical application, the TEMT framework, along with its implementation detailsand part of the simulation data, is made publicly accessible at https://github.com/yehaowei/temt.

Multimodal imaging diagnosis and analysis of prognostic factors in patients with adult-onset Coats disease

AIM:To describe the multimodal imaging features,treatment,and outcomes of patients diagnosed with adultonset Coats disease.METHODS:This retrospective study included patients first diagnosed with Coats disease at≥18 years of age between September 2017 and September 2021.Some patients received anti-vascular endothelial growth factor(VEGF)therapy(conbercept,0.5 mg)as the initial treatment,which was combined with laser photocoagulation as needed.All the patients underwent best corrected visual acuity(BCVA)and intraocular pressure examinations,fundus color photography,spontaneous fluorescence tests,fundus fluorescein angiography,optical coherence tomography(OCT),OCT angiography,and other examinations.BCVA alterations and multimodal image findings in the affected eyes following treatment were compared and the prognostic factors were analyzed.RESULTS:The study included 15 patients who were aged 24-72(57.33±12.61)y at presentation.Systemic hypertension was the most common associated systemic condition,occurring in 13(86.7%)patients.Baseline BCVA ranged from 2.0 to 5.0(4.0±1.1),which showed improvement following treatment(4.2±1.0).Multimodal imaging revealed retinal telangiectasis in 13 patients(86.7%),patchy hemorrhage in 5 patients(33.3%),and stage 2B disease(Shield’s staging criteria)in 11 patients(73.3%).OCT revealed that the baseline central macular thickness(CMT)ranged from 129 to 964μm(473.0±230.1μm),with 13 patients(86.7%)exhibiting a baseline CMT exceeding 250μm.Furthermore,8 patients(53.3%)presented with an epiretinal membrane at baseline or during follow-up.Hyper-reflective scars were observed on OCT in five patients(33.3%)with poor visual prognosis.Vision deteriorated in one patient who did not receive treatment.Final vision was stable in three patients who received laser treatment,whereas improvement was observed in one of two patients who received anti-VEGF therapy alone.In addition,8 of 9 patients(88.9%)who received laser treatment and conbercept exhibited stable or improved BCVA.CONCLUSION:Multimodal imaging can help diagnose adult-onset Coats disease.Anti-VEGF treatment combined with laser therapy can be an option for improving or maintaining BCVA and resolving macular edema.The final visual outcome depends on macular involvement and the disease stage.

Approximate constructions of counterdiabatic driving with NMR quantum systems

Counterdiabatic driving (CD) offers a fast and robust route to manipulate quantum systems, which has widespreadapplications in quantum technologies. However, for higher-dimensional complex systems, the exact CD term involving thespectral properties of the system is difficult to calculate and generally takes a complicated form, impeding its experimentalrealization. Recently, many approximate methods have been proposed for designing CD passages in many-body systems. Inthis topical review, we focus on the CD formalism and briefly introduce several experimental constructions and applicationsof approximate CD driving in spin-chain models with nuclear magnetic resonance (NMR) systems.

A comprehensive and systematic analysis of Dihydrolipoamide S-acetyltransferase (DLAT) as a novel prognostic biomarker in pan-cancer and glioma

Background:Dihydrolipoamide S-acetyltransferase(DLAT)is a subunit of the pyruvate dehydrogenase complex(PDC),a rate-limiting enzyme complex,that can participate in either glycolysis or the tricarboxylic acid cycle(TCA).However,the pathogenesis is not fully understood.We aimed to perform a more systematic and comprehensive analysis of DLAT in the occurrence and progression of tumors,and to investigate its function in patients’prognosis and immunotherapy.Methods:The differential expression,diagnosis,prognosis,genetic and epigenetic alterations,tumor microenvironment,stemness,immune infiltration cells,function enrichment,single-cell analysis,and drug response across cancers were conducted based on multiple computational tools.Additionally,we validated its carcinogenic effect and possible mechanism in glioma cells.Results:We exhibited that DLAT expression was increased in most tumors,especially in glioma,and affected the survival of tumor patients.DLAT was related to RNA modification genes,DNA methylation,immune infiltration,and immune infiltration cells,including CD4+T cells,CD8+T cells,Tregs,and cancer-associatedfibroblasts.Single-cell analysis displayed that DLAT might regulate cancer by mediating angiogenesis,inflammation,and stemness.Enrichment analysis revealed that DLAT might take part in the cell cycle pathway.Increased expression of DLAT leads tumor cells to be more resistant to many kinds of compounds,including PI3Kβinhibitors,PKC inhibitors,HSP90 inhibitors,and MEK inhibitors.In addition,glioma cells with DLAT silence inhibited proliferation,migration,and invasion ability,and promoted cell apoptosis.Conclusion:We conducted a comprehensive analysis of DLAT in the occurrence and progression of tumors,and its possible functions and mechanisms.DLAT is a potential diagnostic,prognostic,and immunotherapeutic biomarker for cancer patients.

Exploring the anti-osteoporotic potential of simvastatin and metformin: a comprehensive Mendelian randomization and animal experiment investigation

Background:Both simvastatin and metformin have demonstrated potential efficacy in osteoporosis(OP)treatment.However,there is a lack of systematic studies comparing their anti-osteoporotic effects.This study aims to compare the effects of simvastatin and metformin on OP through Mendelian randomization(MR)studies and animal experiments.Methods:Initially,we will analyze the causal impact of simvastatin or metformin treatment on OP prevalence and three common clinical OP diagnostic markers(bone mineral density(BMD),serum osteocalcin(OCN),and tartrate-resistant acid phosphatase(TRAP)levels)using genome-wide association study(GWAS)summary statistics.Additionally,we established animal models to further analyze and compare the anti-osteoporosis effects of simvastatin and metformin.8 male C57BL/6J mice(3-month-old)and 24 male C57BL/6J mice(18-month-old)were treated with simvastatin or metformin for 12 weeks.OP pathology was assessed using histology,immunohistochemistry,biomechanical tests,micro-computed tomography,and osteogenic differentiation assays.Results:In the MR analysis,metformin treatment was significantly associated with lower OP prevalence(OR(95%CI)=0.933(0.902–0.965),β=-0.0694,P<0.001)and higher BMD(OR(95%CI)=3.719(1.750–7.908),β=1.3136,P<0.001).In the animal experiment,both drugs increased bone mass,improved bone microstructure,and promoted osteoblast differentiation.However,metformin appeared more effective in several aspects.It significantly inhibited bone marrow adipocyte and osteoclast differentiation in aged mice compared to simvastatin.Additionally,metformin better promoted the expression of osteoprotegerin(OPG)and collagen type I(Col-I)in bone tissue and maintained the structure and biomechanical properties of cancellous bone.Conclusion:Both drugs significantly preserved bone homeostasis.Particularly,compared with simvastatin,metformin exhibited superior effects in inhibiting adipogenesis,enhancing the OPG/RANKL pathway,and promoting cancellous bone reconstruction.Metformin may serve as a valuable adjunct in preventing and treating OP in the elderly.

预旋整流栅对90°弯管流动均匀性及离心压缩机性能影响的试验研究

本文在离心压缩机进口前加旋绕式整流栅,通过PIV可视化试验,研究预旋整流栅对90°弯管出口流道及离心压缩机性能影响。结果表明:在90°弯管前安装旋绕式整流栅能有效改善弯管后流动的均匀性。当离心压缩机运行在较小马赫数下,安装整流栅时,离心压缩机效率基本保持不变或者略有降低。当离心压缩机运行在较大马赫数下,安装有右旋整流栅时,离心压缩机的效率得到提高;安装左旋整流栅时,离心压缩机效率略有提高同时和压比得到较大幅度的提高。

全息影像技术在机器人辅助腹腔镜下肾部分切除术治疗肾门部肿瘤中的应用

目的评价全息影像技术引导机器人辅助腹腔镜下肾部分切除术(RAPN)治疗肾门部肿瘤的可行性与有效性。方法回顾性分析该院2019年6月-2019年10月收治的11例肾门部肿瘤患者的临床资料。其中,男3例,女8例;左侧4例,右侧7例;患者年龄32~75岁,平均62.6岁,体质指数19.45~28.12 kg/m^2,平均23.75 kg/m^2,肿瘤直径1.1~6.7 cm,平均2.76 cm,R.E.N.A.L.评分8~12分,平均10.7分,患肾肾小球滤过率(GFR)22~51 mL/min,平均35 mL/min。患者术前行全腹部增强CT,利用CT数据进行全息影像重建。术中应用该技术结合达芬奇机器人辅助系统,精准分离、剜除肿瘤,并记录手术持续时间、出血量、肾脏热缺血时间、有无并发症及切缘阳性率等。结果根据全息影像引导,11例患者均顺利剜除肿瘤,完成手术,无中转开放。手术时间60~130 min,平均90 min。术中出血量50~180 mL,平均100 mL,热缺血时间18~25 min,平均21 min,无术后发热、继发出血或漏尿等并发症。术后病理诊断肾透明细胞癌9例(FuhrmanⅠ和Ⅱ级),乳头状细胞癌1例,血管平滑肌脂肪瘤1例,无切缘阳性病例。术后随访3~7个月,平均4.3个月,患肾GFR 18~43 mL/min,平均31 mL/min。术后3个月复查肾脏CT平扫及增强,全部患者未出现复发。结论全息影像技术引导RAPN治疗肾门部肿瘤,围手术期并发症少,安全有效。

Investigating the Transport Mechanism of PM2.5 Pollution during January 2014 in Wuhan, Central China

Severe haze pollution that occurred in January 2014 in Wuhan was investigated. The factors leading to Wuhan’s PM2.5 pollution and the characteristics and formation mechanism were found to be significantly different from other megacities, like Beijing. Both the growth rates and decline rates of PM2.5 concentrations in Wuhan were lower than those in Beijing, but the monthly PM2.5 value was approximately twice that in Beijing. Furthermore, the sharp increases of PM2.5 concentrations were often accompanied by strong winds. A high-precision modeling system with an online source-tagged method was established to explore the formation mechanism of five haze episodes. The long-range transport of the polluted air masses from the North China Plain (NCP) was the main factor leading to the sharp increases of PM2.5 concentrations in Wuhan, which contributed 53.4% of the monthly PM2.5 concentrations and 38.5% of polluted days. Furthermore, the change in meteorological conditions such as weakened winds and stable weather conditions led to the accumulation of air pollutants in Wuhan after the long-range transport. The contribution from Wuhan and surrounding cities to the PM2.5 concentrations was determined to be 67.4% during this period. Under the complex regional transport of pollutants from surrounding cities, the NCP, East China, and South China, the five episodes resulted in 30 haze days in Wuhan. The findings reveal important roles played by transregional and intercity transport in haze formation in Wuhan.

Catalytic conversion of lignocellulosic biomass into chemicals and fuels

In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future,lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock.This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels.Following a brief introduction on the structure,major resources and pretreatment methods of lignocellulosic biomass,the catalytic conversion of three main components,i.e.,cellulose,hemicellulose and lignin,into various compounds are comprehensively discussed.Either in separate steps or in one-pot,cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF,furfural,polyols,and organic acids,or even nitrogen-containing chemicals such as amino acids.On the other hand,lignin is first depolymerized into phenols,catechols,guaiacols,aldehydes and ketones,and then further transformed into hydrocarbon fuels,bioplastic precursors and bioactive compounds.The review then introduces the transformations of whole biomass via catalytic gasification,catalytic pyrolysis,as well as emerging strategies.Finally,opportunities,challenges and prospective of woody biomass valorization are highlighted.

Rock brittleness indices and their applications to different fields of rock engineering:A review

Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness.As such,it is of high practical value to correctly evaluate rock brittleness.However,the definition and measurement method of rock brittleness have been very diverse and not yet been standardized.In this paper,the definitions of rock brittleness are firstly reviewed,and several representative definitions of rock brittleness are identified and briefly discussed.The development and role of rock brittleness in different fields of rock engineering are also studied.Eighty brittleness indices publicly available in rock mechanics literature are compiled,and the measurement method,applicability and limitations of some indices are discussed.The results show that(1)the large number of brittleness indices and brittleness definitions is attributed to the different foci on the rock behavior when it breaks;(2)indices developed in one field usually are not directly applicable to other fields;and(3)the term“brittleness”is sometimes misused,and many empirically-obtained brittleness indices,which lack theoretical basis,fail to truly reflect rock brittleness.On the basis of this review,three measurement methods are identified,i.e.(1)elastic deformation before fracture,(2)shape of post-peak stressestrain curves,and(3)methods based on fracture mechanics theory,which have the potential to be further refined and unified to become the standard measurement methods of rock brittleness.It is highly beneficial for the rock mechanics community to develop a robust definition of rock brittleness.This study will undoubtedly provide a comprehensive timely reference for selecting an appropriate brittleness index for their applications,and will also pave the way for the development of a standard definition and measurement method of rock brittleness in the long term.

Role of Sclerostin in the Bone Loss of Postmenopausal Chinese Women with Type 2 Diabetes

Objective To evaluate the role of sclerostin in bone loss of postmenopausal Chinese women with type 2 diabetes me｜litus. Methods The postmenopausal patients suffering from type 2 diabetes mellitus and age, body mass index, and duration of menopause matched healthy controls were enrolled into this cross-sectional study according to criteria of inclusion and exclusion.

Role of peroxisome proliferator-activated receptors gene polymorphisms in type 2 diabetes and metabolic syndrome

Metabolic syndrome(MetS) and type 2 diabetes mellitus(T2DM) are the serious public health problems worldwide.Moreover,it is estimated that MetS patients have about five-fold greater risk of the T2 DM development compared with people without the syndrome.Peroxisome proliferator-activated receptors are a subgroup of the nuclear hormone receptor superfamily of ligand-activated transcription factors which play an important role in the pathogenesis of MetS and T2 DM.All three members of the peroxisome proliferator-activated receptor(PPAR) nuclear receptor subfamily,PPARα,PPARp/5 and PPARγ are critical in regulating insulin sensitivity,adipogenesis,lipid metabolism,and blood pressure.Recently,more and more studies indicated that the gene polymorphism of PPARs,such as Leu^(162)Val and Val^(227)Ala of PPARα,+294T> C of PPARβ/δ,Pro^(12)Ala and C1431 T of PPARγ,are significantly associated with the onset and progressing of MetS and T2 DM in different population worldwide.Furthermore,a large body of evidence demonstrated that the glucose metabolism and lipid metabolism were influenced by gene-gene interaction among PPARs genes.However,given the complexity pathogenesis of metabolic disease,it is unlikely that genetic variation of a single locus would provide an adequate explanation of inter-individual differences which results in diverse clinical syndromes.Thus,gene-gene interactions and gene-environment interactions associated with T2 DM and MetS need future comprehensive studies.

Studies on the evolution process of rockbursts in deep tunnels

This paper focuses on the evolution processes of different types of rockbursts occurring in deep tunnels. A series of laboratory tests and in-situ monitoring in deep tunnels excavated by tunnel boring machine （TBM） and drill-and-blast （D＆B） method have been conducted to understand the mechanisms and processes of the evolution of different types of rockbursts, including strain rockburst, strain-structure slip rockburst, immediate rockburst and time-delayed rockburst. Three different risk assessment methods are proposed to evaluate the intensity and potential failure depth of rockbursts. These methods can be applied before excavation and the results can be updated according to the real-time information during excavation. Two micro-seismicity based real-time warning systems have been established for predicting various intensities ofrockbursts, such as slight, moderate, intensive and extremely intensive rockbursts. Meanwhile, the probability and intensity of the rockburst are also given. The strategy for excavation and support design has been suggested for various intensities of rockbursts before excavation. The strategy for dynamic control of the rockburst evolution process is also proposed according to the monitoring results. The methodology has been successfully applied to rockburst risk reduction for deep tunnels at Jinping II hydropower project. The results have illustrated the applicability of the proposed methodology and techniques concerning rockbursts.

Deformation and failure characteristics and fracture evolution of cryptocrystalline basalt

Cryptocrystalline basalt is one of the two major types of rocks exposed in the super large-scale underground powerhouse in Baihetan hydropower station in China.The rock of this type shows various sitespecific mechanical responses(e.g.fragmentation,fracturing,and relaxation)during excavation.Using conventional triaxial testing facility MTS 815.03,we obtained the stressestrain curves,macroscopic failure characteristics,and strength characteristics of cryptocrystalline basalt.On this basis,evolution of crack initiation and propagation was explored using the finite-discrete element method(FDEM)to understand the failure mechanism of cryptocrystalline basalt.The test results showed that:(1)under different confining stresses,almost all the pre-peak stressestrain curves of cryptocrystalline basalt were linear and the post-peak stresses decreased rapidly;(2)the cryptocrystalline basalt showed a failure mode in a form of fragmentation under low and medium confining stresses while fragmentation-shear coupling failure dominated at high confining stresses;and(3)the initial strength ratio(sci/sf,where sci and sf are the crack initiation strength and peak strength,respectively)ranged from 0.45 to 0.55 and the damage strength ratio(scd/sf,where scd is the crack damage strength)exceeded 0.9.The stressestrain curve characteristics and failure modes of cryptocrystalline basalt could be reflected numerically.For this,FDEM simulation was employed to reveal the characteristics of cryptocrystalline basalt,including high scd/sf values and rapid failure after scd,with respect to the microscopic characteristics of mineral structures.The results showed that the fragmentation characteristics of cryptocrystalline basalt were closely related to the development of tensile cracks in rock samples prior to failure.Moreover,the decrease in degree of fragmentation with increasing confining stress was also correlated with the dominant effect of confining stress on the tensile cracks.

Effects of bolt profile and grout mixture on shearing behaviors of bolt-grout interface

Shearing behavior and failure mechanism of bolt-grout interface are of great significance for load transfer capacity and design of rock bolting system.In this paper,direct shear tests on bolt-grout interfaces under constant normal load(CNL) conditions were conducted to investigate the effects of bolt profile(i.e.rib spacing and rib height) and grout mixture on the bolt-grout interface in terms of mechanical behaviors and failure modes.Test results showed that the peak shear strength and the deformation capacity of the bolt-grout interface are highly dependent on the bolt profile and grout mixture,suggesting that bolt performances can be optimized,which were unfortunately ignored in the previous studies.A new interface failure mode,i.e.'sheared-crush' mode,was proposed,which was characterized by progressive crush failure of the grout asperities between steel ribs during shearing.It was shown that the interface failure mode mainly depends on the normal stress level and rib spacing,compared with the rib height and grout mixture for the range of tested parameters in this study.