The stability of rock slopes is frequently controlled by the initiation and propagation of inherent dominant cracks. This study systematically investigated these processes in valley slopes by combining fracture-mechanics analysis with transparent soil model tests. An analytical expression for the stress field at the dominant crack tip was derived from the slope stress distribution by superposing the corresponding stress intensity factors (SIFs). The theoretical predictions were then validated against observations from transparent soil model tests. The influences of slope angle (β), crack inclination angle (α), crack position parameter (b), and crack length parameter (h) on crack initiation and propagation were quantified. The results indicated that: (1) cracks at the slope crest tended to propagate in shear mode, and the shear crack initiation angle (θs) was approximately 8°. Cracks at the slope toe might propagate in either tensile or shear mode. (2) θs at the slope crest increased with β, b, and l, and decreased with α. The maximum change in θs induced by the considered parameters was approximately 30°. (3) The tensile crack initiation angle (θt) at the slop toe decreased with β, α, and l, while the influence of b was comparatively minor. The maximum change in θt caused by individual parameters ranged approximately from 25° to 60°. Predicted crack propagation modes and directions showed good agreement with experimental results. These findings provide theoretical guidance for stability assessments of valley slopes controlled by dominant crack propagation.

This study employs our proposed numerical method for dynamic crack propagation based on the smeared fracture model to investigate crack propagation and slope deformation evolution in a deep valley slope. The method was first validated against model test results. Then, we analyzed slope deformation evolution based on dominant crack propagation. Finally, the effects of crack dip angle, trace length and random crack distribution on dominant crack propagation and slope deformation were discussed. The results show that the dominant crack at the slope crest (crest-dominant crack) propagates downward in shear-mode at a small angle, smoothly exiting the middle-lower slope face in an arc, whereas the dominant crack at the slope toe (toe-dominant crack) propagates upward in tensile-mode at a large angle, forming an irregular zigzag through-going path from the middle-upper slope face. The crest-dominant crack drives forward and outward deformation from its tip and slope crest, sharply increasing overall deformation with retrogressive features, whereas the toe-dominant crack induces creeping deformation above the crack before a sharp increase near the slope surface, also exhibiting retrogressive behavior. Trace length and dip angle of dominant crack have little effect on propagation mode, segment morphology, and slope deformation pattern, but significantly control propagation path distribution. For the crest-dominant crack, longer length or larger dip angle shifts shear-out forward and enlarges the failure zone; for the toe-dominant crack, longer length or smaller dip angle shifts through-going toward the slope crest, also enlarging the failure zone. Random cracks significantly affect dominant crack propagation, the crest-dominant crack follows an approximately stepped path, yielding a much larger failure zone than without random cracks, while the toe-dominant crack follows an irregular zigzag path with a comparable failure zone. This study provides a theoretical basis for the failure mechanism analysis of fractured rock slope under complex environmental conditions.

To study the degree of strength parameter deterioration (DSPD) of Lushi swelling rock in the high slope area under wetting-drying cycles, 114 samples are remodeled. Wetting-drying cycle and triaxial tests are conducted to comprehensively analyze the influence of dry density, wetting-drying cycle path, and number of wetting-drying cycles on the strength deterioration characteristics of Lushi swelling rock. Using the fitting analysis and function superposition methods, the DSPD model of Lushi swelling rock under wetting-drying cycles is established, which considers the previous four influencing factors. The influence of the DSPD of Lushi swelling rock on the stability of high slopes under rainfall seepage and circulation conditions is studied. Lushi swelling rock exhibits significant strength deterioration characteristics under wetting-drying cycles. The overall DSPD for cohesion is higher than that of the internal friction angle. Under rainstorm conditions, strength deterioration leads to a shallower depth of the critical slip surface of the slope and a smaller safety factor. After eight rounds of rainfall seepage and circulation, the safety factor gradually decreases by approximately 14%-28%. This study provides and verifies the DSPD model of Lushi swelling rock under wetting-drying cycles, and the results could provide a basis for disaster prediction and the optimization design of swelling rock slopes.

The discrete element method (DEM) represents a crucial numerical simulation approach for investigating the internal damage mechanisms of rocks. However, in order to construct an accurate simulation model, it is essential to set the correct microscopic parameters. Consequently, parameter calibration has emerged as a key area of focus within this field. The existing parameter calibration methods have yielded satisfactory results; however, there is still scope for further improvement and advancement. In this study, a novel intelligent parameter calibration method has been proposed, combining the benefits of the BP neural network and genetic algorithm (GA). The method constructs a parameter relationship model with micro-parameters as inputs and macro-parameters as outputs. Then GA is employed to invert the relationship model to calculate the parameter calibration. The results demonstrate that the method is capable of calculating a set of high-precision micro-parameter solutions in a mere 2 min, with the majority of its errors being within 5%.

As an innovative technology, transparent soil similar material can actively promote the development of soil model experiments by clarifying the structure, ratio, and strength characteristics. In order to study the factors affecting the mechanical properties of transparent soil materials, fused quartz is chosen as the aggregate material, nano-scale hydrophobic fumed silica is used as the binder, and a mixture of dodecane and No. 15 white oil is employed as the constituent material for transparent soils. In this study, indoor direct shear tests are conducted, and the range method is used to analyze the factors of quartz particle size, binder content and proportion, moisture content and dry density of the mixture solution. The relationship between the strength properties of transparent soil material and the above variables are quantitatively investigated. The results show that the transparent soil similar material can exhibit softening or hardening properties by changing the proportion of influencing factors, which can be suitable to most soils. Dry density has the most significant impact on cohesion while particle size of quartz has the greatest influence on the internal friction angle. The strength parameter of transparent soil has exponential distribution relationship with moisture content and linear distribution relationship with dry density. The cohesion and powder content are distributed exponentially while the internal friction angle and powder content are linearly distributed. As the particle size of quartz increases, the cohesion decreases overall and the internal friction angle increases. The strength parameters of transparent soil have a logarithmic distribution relationship with the unevenness coefficient of particle size and a linear relationship with the curvature coefficient of particle size. This study has established a quantitative control relationship between the key parameters of transparent soil materials and their mechanical properties. The revealed correlations between gradation of particles and strength parameters can serve as a guideline for simulation and visualization techniques based on transparent soils. It is of great significance for the visualization of the evolution mechanisms of geotechnical disasters.

Rock slope failures occur frequently in mountainous regions. However, research on the internal deformation and failure evolution mechanism of fractured valley rock slopes caused by dominant crack propagation remains limited. To address this knowledge gap, this study used the bank slope of the newly constructed Nujiang Grand Bridge as a prototype to perform model tests on slopes with dominant cracks at the slope top (M1 model) and slope toe (M2 model) utilizing a self-developed visualized model experiment system. Experimental data from the top load and displacement cells, along with the Particle Image Velocimetry (PIV) technique, were utilized to analyze the load-displacement response curves, displacement, velocity, strain rate fields, and propagation characteristics of the dominant crack in the slope. The results indicated that: (1) the load-displacement curves for both M1 and M2 models could be divided into four stages: slow acceleration, approximately uniform increase, slow deceleration, and rapid decline. The ultimate bearing capacity of theM2 model was about 3.2 kN larger than that of the M1 model. (2) The deformation and failure process of the slopes in both models could be categorized into three stages: initial deformation, rapid deformation, and failure. The M1 and M2 models exhibited "thrust- type" and "retrogressive" landslide failure characteristics, respectively. (3) The length of the dominant crack propagation segment increased exponentially with increasing loading duration, and the slope deformation showed obvious zonal characteristics. (4) The comparison of deformation and failure characteristics between the model and prototype slopes validated the rationality and accuracy of the model test. This study offers valuable insights into the internal deformation and failure evolution mechanism of fractured valley slopes resulting from dominant crack propagation.

[Objective]Internal fractures serve as a major predisposing factor and early indicator of slope failures.Understanding how the inclination of such fractures influences slope deformation and failure mechanisms is essential for interpreting the initiation of slope hazards and is critical for accurate prediction and early warning.This study aims to investigate the effect of the dip angle of pre-existing frontal fractures on the deformation evolution and failure patterns of slopes,thereby providing a theoretical basis for stability evaluation and disaster prevention.[Methods]In this study,the influence of leading edge fissure inclination on slope deformation evolution law is investigated based on the transparent similar model test technique which was employed to simulate slope behavior under controlled loading conditions.Three physical slope models containing artificial fractures with dip angles of 19°,27.5°,and 35° were constructed using a transparent soil material.This material employs fused quartz sand of varying particle sizes as the skeletal framework,nanoscale hydrophobic silica powder as the cementing agent,and a pore fluid composed of a mixture of n-dodecane and white oil.After mixing and stirring,it forms an artificially mixed soil that can be used to simulate soft rock.A loading system was used to apply a constant External Load at the crest of the slope to simulate external disturbances.High-resolution digital image correlation(DIC)and acoustic emission(AE)particle tracking techniques were used to monitor and quantify internal deformation fields,crack initiation,propagation paths,and failure mechanisms in real time.The experiments allowed detailed observation of the entire process from initial compression through crack development to ultimate failure.[Results]The experimental results showes that:1)Slope deformation damage presents"compaction-fissure expansion-penetration damage"three-stage evolution law,and the fissure expansion follows the fracture mechanics mechanism of"cracking-expansion-penetration";2)Fracture inclination significantly affects the slope damage pattern,the lower inclination angle(19°)is dominated by a single"inverted y-type"slip surface,which is characterized by overall slip;the medium inclination angle(27.5°)forms a double rupture zone with coordinated damage;and the higher inclination angle(35°)develops into a shear-tension composite type of damage accompanied by an asymmetric displacement zoning;3)The fissure expansion path is significantly affected by the inclination angle,and the expansion path is close to the back edge of the slope body and the damage range is larger under medium-low inclination angle,while the damage mode changes to shallow high-speed sliding under higher inclination angle.The results provide a theoretical basis for the stability assessment and disaster prevention of slopes with leading edge fissures.[Conclusions]This study demonstrates that the inclination of pre-existing frontal fractures plays a critical role in controlling the deformation behavior and failure mechanisms of slopes.The findings enhance the understanding of fracture-dominated slope instability and provide a scientific basis for improving monitoring systems and reinforcement designs for vulnerable slopes.The proposed methodology and results contribute to more accurate hazard assessment and disaster mitigation strategies in geotechnical engineering.

Occurrence of loess landslide has been more frequent due to the drastic global climate change, rapid expansion of human disturbances and continuous intensification of engineering activities. The activation and evolution mechanisms of the loess landslides under the rainfall are yet to be studied. In this paper, with reference to the Yangpoyao slope with seepage fissures under rainfall, an adjustable-angle landslide model test system is developed, integrating the rainfall simulation system, the measurement system and the data acquisition system, and the deformation development of the model, the rainfall infiltration, the change of water content and the destructive process of the model are monitored by the monitoring technology of multi-means and multi-methods throughout the course of the disaster. A distributed fibre-optic sensor system with the characteristics of continuity and high precision is used to monitor the temperature and strain within the slope model. The deformation evolution mechanism of fissured loess slopes under rainfall was elucidated through the observation of experimental phenomena and the analysis of the internal strain values of the soil, as measured by fibre optic sensors. The experimental results show that the collapse process of loess slopes can be categorised into three types, i.e. sinkhole collapse, block collapse and gully collapse, and that the deformation and damage patterns of the loess landslide model are mainly caused by shallow soil movement induced by erosion. Through the comparative analysis of the model test and the photographs of the field investigation, it is further demonstrated that the damage pattern shown in the physical model test is basically consistent with the slope condition of the real Yangpoyao slope, which provides a new theoretical reference for natural disaster prediction and management of loess slopes and landslides.

The utilisation of particle flow code to establish discrete element models represents an effective approach for addressing the issue of discontinuous media. This methodology has been employed by numerous scholars to analyse the mechanical properties and damage laws of geotechnical materials. However, the complex nature of the particle action mechanism within the discrete element model necessitates a considerably longer time frame for the completion of an elaborate simulation experiment than that required for a laboratory test. This presents a significant challenge for researchers seeking to investigate the mechanical properties of a large number of geotechnical materials through the discrete element method. In order to accelerate the prediction of mechanical properties for various specific discrete element models, a mathematical model of the geotechnical micro-parameters and the geotechnical strength macro-parameters has been developed using an orthogonal design considering interactions and a back propagation neural network based on Bayesian regularisation. The geotechnical strength macro-parameters, such as compressive strength and tensile strength, can be derived directly from the geotechnical micro-parameters of the discrete element models through this mathematical model. The results show that the trained network model demonstrates an aptitude for predicting the uniaxial compressive strength, tensile strength, cohesion, and friction angle of geotechnical materials. The mean square error is 11.611 for the training set and 14.207 for the test set. In the test set, the median deviation rates of the predicted values of the four strength macro-parameters from the target values are 3.90

静压沉桩过程中沉桩速率决定着桩周土体扰动程度与范围,而目前在静压沉桩中考虑沉桩速率对桩周土体变形影响的研究还较少.基于透明土相似材料和粒子图像测速技术(PIV),开展静压沉桩可视化模型试验研究,分析不同沉桩速率下桩周土体位移场及其演化过程.结果表明:不同沉桩速率下桩周土体位移模式表现出斜向下挤密扩张→侧向挤压→斜向上挤出的动态变化过程;沉桩初期和后期扰动范围发生变化的原因是高速沉桩下桩端下提前产生了高应力区;高速沉桩对桩周土体扰动范围略大于低速沉桩;桩周土体总的运动趋势为向上运动,且沉桩速率越大,距离桩体越近,土体竖向位移量越大.研究成果可为合理设计沉桩速率和保障施工质量与安全提供技术支持.

The ultimate bearing capacity is one of the most important mechanical parameters in the mining and geotechnical fields and has a vital influence on the stability of slopes and the safety of constructions and structures. The determination of the ultimate bearing capacity has become a controversial issue in slope engineering. This study proposes a way to obtain the ultimate bearing capacity of a multilayer slope with horizontal stratification. According to limit analysis theory, three typical multiblock sliding failure modes for a multilayer slope with horizontal stratification are established. The upper limit solution of the ultimate bearing capacity of a multilayer slope, considering the influence of horizontal stratification, is derived. The optimization procedure is carried out to obtain the optimal value of the ultimate bearing capacity by using the sequential quadratic programming algorithm. The accuracy of the present method is proven based on a comparison of calculation results using other analytical methods and the numerical simulation method. The influence analysis of the parameters, involving the slope angle, soil strength, and distance of the foundation from the slope shoulder, is performed. The results indicate that the error between the calculated results of the present method and those of numerical simulation, as well as the error between the calculated results of the present method and those of other existing methods, is less than 10%. The ultimate bearing capacity linearly decreases with increasing slope angle, while it linearly increases with increasing distance of the foundation from the slope shoulder. The analytical method provides a method to analyze the ultimate bearing capacity of a multilayer slope, which effectively solves the problem of heterogeneity of soil layers observed in the natural slope. The results from this study can be used as a guide to estimate the stability of the slope and design of the foundation on a slope considering the load action near the slope.

The deformation and failure evolution process of rock slope during disaster incubation period is controlled by internal long fissures (controlling fissures), and the evolution mechanism is of great significance for the prevention of landslide disasters. Based on the transparent physical model experiment technology, two typical rock slopes with controlling fissures (one with a steep fissure at the back and the other with a gently inclined fissure at the front) were selected as the objects, and the evolution process of deformation and failure inside the slopes was studied through physical model experiments using the self-developed equipment. The displacement rate and strain rate were taken as the characterization quantities of the deformation and fissure propagation, and the spatiotemporal evolution mechanism under the influence of fissures was analyzed with the reference of the common slope without controlling fissure. The conclusions are: (1) The reliability of the proposed experiment method in the study of the deformation and failure evolution process inside the slopes was verified through the simulation of internal deformation accumulation and progressive process of fissure initiation, propagation, and penetration. (2) The deformation and failure process of the slopes with controlling fissures is similar to that of the slope without controlling fissures and can be divided into four stages: deformation accumulation, failure band/fissure initiation, failure band/fissure expansion adjustment, and rapid expansion and penetration of failure bands/fissures. (3) The tip of steep fissure at the back undergoes a tensile-shear mixed initiation and expands downward due to the pushing action induced by initial fissure slip deformation, while the tip of gently inclined fissure at the front undergoes tensile initiation and expands upward due to the traction induced by initial fissure slip deformation. The propagation rates of fissures increase exponentially with the increasing length of fissures. (4) The fissure propagation modes change with the evolution of slope deformation and fissure propagation. The steep fissure at the back starts to propagate in tensile-shear mixed mode and turns to propagate in shear mode, and finally shears out near the slope toe. The gently inclined fissure at the front firstly propagates in tensile mode and then transforms to shear mode, and finally intersects with the failure zone at the back.

Transparent soil prepared using fused quartz sand as skeleton material, nano hydrophobic gas-phase silica powder as cementing agent, and the mixed mineral oil of n-dodecane and No.15 white oil as pore fluid, has good transparency and moderate strength and serves an ideal similar material to carry out the deformation development process and failure mechanism of geotechnical engineering physical model. Aiming at the main factors affecting the strength characteristics of the new transparent soil, the influence of water content and quartz sand particle size on the material strength is studied by direct shear test, and the mesostructure mechanism of the strength is analyzed via optical microscopic photos. The results show that: ①The displacement-force curve of transparent soil samples show softening characteristics under low axial pressure but show hardening characteristics under high axial pressure. ②Moisture content has a significant effect on cohesion of transparent soil, but has little influence on the internal friction angle, and the optimum moisture content of the transparent soil is about 23%. ③As the particle size of the quartz sand increases, the cohesion decreases linearly, while the internal friction angle first decreases slowly and then increases rapidly. ④The pore size and the cementation of powder and liquid mixture affect the cohesion of the transparent soil on the microstructure, whereas the occlusion and interlocking of the agglomerated quartz sand particles and the lubrication of the quartz sand influence the internal friction angle of the transparent soil.

岩土体结构的破坏是由于施加能量超过变形能阈值所造成,基于能量的结构性参数更有利于反映结构性的本质特征.对不同含水状态,不同干密度的延安桃花山原状与压实重塑黄土进行了侧限压缩试验,发现孔隙比e与竖向压力P在ln(1+e)-lgP双对数坐标系内有良好的分段线性关系.在此基础上,基于应变能密度理论,推导提出了侧限压缩条件下的结构性参数映射能,并将该参数推广至复杂加载条件.进一步通过多个区域内,原状与重塑,不同含水率,不同干密度,不同埋深深度,不同粒度土体的侧限压缩试验结果,以及不同含水率土体的等向压缩试验结果,对提出结构性参数的合理性进行了验证.结果表明提出的结构性参数映射能物理意义明确,且能准确地定量表征不同状态,不同试验条件下土体的结构性.

Ultimate bearing capacity has always been a difficult and hot issue in mining and rock and soil fields, which seriously affects the safety and stability of slope and adjacent slope structures. Based on the upper bound theorem of limit analysis, the failure mechanism of heterogeneous layered slope with rigid multi-sliders was established in three modes. The upper bound solution of slope ultimate bearing capacity was deduced, and the optimal value was obtained by sequential quadratic programming algorithm (SQP). The north slope of Sancha mine was taken as the engineering background to verify effectiveness of the proposed method by comparing with the numerical method, and then the influence analysis of two parameters of different slope angles and the distances between dump and slope shoulder was carried out. The results were concluded as follows. (1) The results of the proposed method are in good agreement with those of numerical method, indicating that the proposed upper limit solution of slope ultimate bearing capacity is reasonable and effective. (2) The ultimate bearing capacity of slope has a linear negative correlation with slope angle and a linear positive correlation with the distance between the dump and the slope shoulder. Compared with the distance between the dump and the slope shoulder, the slope angle is more sensitive to the bearing capacity of slope. (3) The change of slope angle has a great influence on the slope failure mode, but the change of the distance between the dump and the slope shoulder has no obvious influence on the slope failure mode. (4) Both slope angle and the distance between the dump and the slope shoulder have an impact on the initial position and the overflow position of the slip surface. The initial position of the slip surface is greatly affected by the distance between the dump and the slope shoulder, but less affected by the slope angle. The overflow position of slip surface is greatly affected by slope angle but less affected by the distance between dump and slope shoulder. Relevant research results are expected to provide theoretical support for slope and adjacent slope foundation design.

地下洞室围岩裂隙遇水侵蚀而引发不同程度的劣化对洞室稳定性具有不利影响.针对此问题,以华北某大型抽水蓄能电站为依托,在地质赋存环境和工程问题分析的基础上,开展了裂隙劣化对支护结构内力及围岩变形的影响规律研究.首先基于滑动裂隙模型,通过考虑裂隙水侵蚀引发的裂隙面静水压力和裂隙面强度、刚度的变化,从理论上分析了裂隙劣化的影响机制.其次借鉴强度折减法的思想,通过对裂隙、锚索、喷砼等多种结构的精细模拟,从数值上研究了裂隙劣化的影响程度.最后通过对比分析两部分的结果,提出了裂隙劣化下支护结构受力和围岩变形的预测模型.研究表明:洞室开挖支护后,裂隙劣化是围岩局部变形发展过大的主要诱发因素,且随着劣化程度的加深表现为:(1)支护结构的内力在与裂隙相交处先呈指数型增长而后趋于平稳,最大增幅为100％～150％;(2)围岩的变形呈指数型增长,其中裂隙的滑移和开裂变形量值增幅为100％～120％,围岩的整体变形量值增幅为30％～40％.大型地下洞室施工和运营期间应当充分考虑裂隙劣化对稳定性的不良影响,忽略其影响可能使工程偏于危险.

通过对卢氏膨胀岩试样开展物理成分、微观结构和膨胀率等试验,研究了岩样泡水后膨胀力的特性及其变化的微观机理.通过X射线衍射试验发现卢氏膨胀岩的矿物成分中黏土含量约占49.1％,其中伊利石、蒙脱石的相对含量近90％,使其表现为较强的亲水性.基于加压膨胀法,设计了4种不同的初始含水率和4种不同干密度,共16组96个试样的膨胀力测试方案,探究了初始含水率和干密度对卢氏膨胀岩膨胀力的影响规律.通过多因素耦合分析方法,采用幂函数拟合初始含水率,指数函数拟合干密度,并给出了双因素膨胀力的拟合公式.通过电镜试验研究了初始含水率对膨胀力影响的微观机理,结果表明:当初始含水率较低时,黏土颗粒遇水膨胀后出现微小裂隙,导致膨胀力急剧增加;随着初始含水率增加,黏土颗粒的粒径由大变小,粗颗粒崩解,细粒含量增加,出现泥化现象,膨胀力缓慢减小.

对于城市地铁及高层建筑基坑工程中的混凝土支撑轴力监测项目,现有规范并未明确监测的布点要求及计算方法,导致在实际工程应用中难以对监测结果进行理论性的分析验证,无法形成确切的工程指导意见.为此,通过对实际工程中的混凝土支撑受力模型进行理论分析,推导得出不同受力方向下的应变计算公式,并依据该计算公式明确传感器的布设要求与数据分析方法,最终形成了一整套完整的监测作业流程.基于上述研究成果,以金华-义乌-东阳市域轨道交通工程为依托进行现场支撑结构监测,通过对全分布式光纤传感器、准分布式光纤布拉格光栅(FBG)传感器以及钢筋计获得的监测数据进行分析,验证了提出的概化理论模型以及计算方法的正确性与有效性.

隧道在施工过程中不可避免的会对地下稳定岩体造成扰动,进一步影响原岩的应力状态及稳定性,故对隧道围岩的地表沉降、拱顶下沉及洞周收敛提出了高严格的标准.为了确保隧道的安全施工,以广西某高速公路岗岭坡双洞隧道的监控量测为研究对象,选用合适的数理方法对监测数据进行回归性建模拟合分析,可以预测围岩及地表的最终位移以及根据位移速率趋势判断隧道进、出口段拱顶及地表沉降随时间的变化规律,较为准确的评价和分析围岩稳定性,分析隧道开挖影响的三维时空效应.

屈服应力是反映材料和易性的重要特征参数之一.依托武汉地铁6号线老关村出入段盾构隧道工程,开展室内盾构渣土塌落度试验,推导考虑塌落度桶形状效应的渣土屈服应力改进预测模型,进而分析不同含水率、不同掺入比和不同角砾含量条件下渣土屈服应力变化规律.结果表明:角砾黏土的塌落度试验值与含水率、泡沫剂掺入比和角砾含量呈正相关关系;通过与实验结果及其他理论模型计算结果对比分析,验证了本文改进模型的有效性;角砾黏土屈服应力与角砾含量呈现负相关,与含水率呈现非线性负相关,与泡沫剂掺入比呈现线性负相关.研究成果可望为土压平衡盾构隧道渣土的合理改良施工提供理论基础,具有一定的理论价值和工程意义.