Large-scale model testing of high-pressure grouting reinforcement for bedding slope with rapid-setting polyurethane

Bedding slope is a typical heterogeneous slope consisting of different soil/rock layers and is likely to slide along the weakest interface.Conventional slope protection methods for bedding slopes,such as retaining walls,stabilizing piles,and anchors,are time-consuming and labor-and energy-intensive.This study proposes an innovative polymer grout method to improve the bearing capacity and reduce the displacement of bedding slopes.A series of large-scale model tests were carried out to verify the effectiveness of polymer grout in protecting bedding slopes.Specifically,load-displacement relationships and failure patterns were analyzed for different testing slopes with various dosages of polymer.Results show the great potential of polymer grout in improving bearing capacity,reducing settlement,and protecting slopes from being crushed under shearing.The polymer-treated slopes remained structurally intact,while the untreated slope exhibited considerable damage when subjected to loads surpassing the bearing capacity.It is also found that polymer-cemented soils concentrate around the injection pipe,forming a fan-shaped sheet-like structure.This study proves the improvement of polymer grouting for bedding slope treatment and will contribute to the development of a fast method to protect bedding slopes from landslides.

Optimal mining sequence for coal faces under a bedding slope:insight from landslide prevention

Repetitive mining beneath bedding slopes is identified as a critical factor in geomorphic disturbances, especially landslides and surface subsidence. Prior research has largely concentrated on surface deformation in plains due to multi-seam coal mining and the instability of natural bedding slopes, yet the cumulative impact of different mining sequences on bedding slopes has been less explored. This study combines drone surveys and geological data to construct a comprehensive three-dimensional model of bedding slopes. Utilizing FLAC3D and PFC2D models, derived from laboratory experiments, it simulates stress, deformation, and failure dynamics of slopes under various mining sequences. Incorporating fractal dimension analysis, the research evaluates the stability of slopes in relation to different mining sequences. The findings reveal that mining in an upslope direction minimizes disruption to overlying strata. Initiating extraction from lower segments increases tensile-shear stress in coal pillar overburdens, resulting in greater creep deformation towards the downslope than when starting from upper segments, potentially leading to localized landslides and widespread creep deformation in mined-out areas. The downslope upward mining sequence exhibits the least fractal dimensions, indicating minimal disturbance to both strata and surface. While all five mining scenarios maintain good slope stability under normal conditions, recalibrated stability assessments based on fractal dimensions suggest that downslope upward mining offers the highest stability under rainfall, contrasting with the lower stability and potential instability risks of upslope downward mining. These insights are pivotal for mining operations and geological hazard mitigation in multi-seam coal exploitation on bedding slopes.

Stability of bedded rock slopes subjected to hydro-fluctuation and associated strength deterioration

Reservoir-induced earthquakes(RIEs)occur frequently in the Three Gorges Reservoir Area(TGRA)and the rock mass strength of the hydro-fluctuation belt(HFB)deteriorates severely due to the reservoirinduced seismic loads.Three models of typical bedded rock slopes(BRSs),i.e.gently(GIS),moderately(MIS),and steeply(SIS)inclined slopes,were proposed according to field investigations.The dynamic response mechanism and stability of the BRSs,affected by the rock mass deterioration of the HFB,were investigated by the shaking table test and the universal distinct element code(UDEC)simulation.Specifically,the amplification coefficient of the peak ground acceleration(PGA)of the slope was gradually attenuated under multiple seismic loads,and the acceleration response showed obvious“surface effect”and“elevation effect”in the horizontal and vertical directions,respectively.The“S-type”cubic function and“steep-rise type”exponential function were used to characterize the cumulative damage evolution of the slope caused by microseismic waves(low seismic waves)and high seismic waves,respectively.According to the dynamic responses of the acceleration,cumulative displacement,rock pressure,pore water pressure,damping ratio,natural frequency,stability coefficient,and sliding velocity of the slope,the typical evolution processes of the dynamic cumulative damage and instability failure of the slope were generalized,and the numerical and experimental results were compared.Considering the dynamic effects of the slope height(SH),slope angle(SA),bedding plane thickness(BPT),dip angle of the bedding plane(DABP),dynamic load amplitude(DLA),dynamic load frequency(DLF),height of water level of the hydro-fluctuation belt(HWLHFB),degradation range of the hydro-fluctuation belt(DRHFB),and degradation shape of the hydro-fluctuation belt(DSHFB),the sensitivity of factors influencing the slope dynamic stability using the orthogonal analysis method(OAM)was DLA>DRHFB>SA>SH>DLF>HWLHFB>DSHFB>DABP>BPT.

Exploring mechanism of hidden,steep obliquely inclined bedding landslides using a 3DEC model:A case study of the Shanyang landslide in Shaanxi Province,China

Catastrophic geological disasters frequently occur on slopes with obliquely inclined bedding structures(also referred to as obliquely inclined bedding slopes),where the apparent dip sliding is not readily visible.This phenomenon has become a focal point in landslide research.Yet,there is a lack of studies on the failure modes and mechanisms of hidden,steep obliquely inclined bedding slopes.This study investigated the Shanyang landslide in Shaanxi Province,China.Using field investigations,laboratory tests of geotechnical parameters,and the 3DEC software,this study developed a numerical model of the landslide to analyze the failure process of such slopes.The findings indicate that the Shanyang landslide primarily crept along a weak interlayer under the action of gravity.The landslide,initially following a dip angle with the support of a stable inclined rock mass,shifted direction under the influence of argillization in the weak interlayer,moving towards the apparent dip angle.The slide resistance effect of the karstic dissolution zone was increasingly significant during this process,with lateral friction being the primary resistance force.A reduction in the lateral friction due to karstic dissolution made the apparent dip sliding characteristics of the Shanyang landslide more pronounced.Notably,deformations such as bending and uplift at the slope’s foot suggest that the main slide resistance shifts from lateral friction within the karstic dissolution zone to the slope foot’s resistance force,leading to the eventual buckling failure of the landslide.This study unveils a novel failure mode of apparent dip creep-buckling in the Shanyang landslide,highlighting the critical role of lateral friction from the karstic dissolution zone in its failure mechanism.These insights offer a valuable reference for mitigating risks and preventing disasters related to obliquely inclined bedding landslides.

Model test and numerical simulation on the dynamic stability of the bedding rock slope under frequent microseisms

Shake table testing was performed to investigate the dynamic stability of a mid-dip bedding rock slope under frequent earthquakes. Then, numerical modelling was established to further study the slope dynamic stability under purely microseisms and the influence of five factors, including seismic amplitude, slope height, slope angle, strata inclination and strata thickness, were considered. The experimental results show that the natural frequency of the slope decreases and damping ratio increases as the earthquake loading times increase. The dynamic strength reduction method is adopted for the stability evaluation of the bedding rock slope in numerical simulation, and the slope stability decreases with the increase of seismic amplitude, increase of slope height, reduction of strata thickness and increase of slope angle. The failure mode of a mid-dip bedding rock slope in the shaking table test is integral slipping along the bedding surface with dipping tensile cracks at the slope rear edge going through the bedding surfaces. In the numerical simulation, the long-term stability of a mid-dip bedding slope is worst under frequent microseisms and the slope is at risk of integral sliding instability, whereas the slope rock mass is more broken than shown in the shaking table test. The research results are of practical significance to better understand the formation mechanism of reservoir landslides and prevent future landslide disasters.

Experimental study on seismic response and progressive failure characteristics of bedding rock slopes

Bedding rock slopes are common geological features in nature that are prone to failure under strong earthquakes. Their failures induce catastrophic landslides and form barrier lakes, posing severe threats to people’s lives and property. Based on the similarity criteria, a bedding rock slope model with a length of3 m, a width of 0.8 m, and a height of 1.6 m was constructed to facilitate large-scale shaking table tests.The results showed that with the increase of vibration time, the natural frequency of the model slope decreased, but the damping ratio increased. Damage to the rock mass structure altered the dynamic characteristics of the slope;therefore, amplification of the acceleration was found to be nonlinear and uneven. Furthermore, the acceleration was amplified nonlinearly with the increase of slope elevation along the slope surface and the vertical section, and the maximum acceleration amplification factor(AAF) occurred at the slope crest. Before visible deformation, the AAF increased with increasing shaking intensity;however, it decreased with increasing shaking intensity after obvious deformation. The slope was likely to slide along the bedding planes at a shallow depth below the slope surface. The upper part of the slope mainly experienced a tensile-shear effect, whereas the lower part suffered a compressive-shear force. The progressive failure process of the model slope can be divided into four stages, and the dislocated rock mass can be summarized into three zones. The testing data provide a good explanation of the dynamic behavior of the rock slope when subjected to an earthquake and may serve as a helpful reference in implementing antiseismic measures for earthquake-induced landslides.

Influence of depth-thickness ratio of mining on the stability of a bedding slope with its sliding surface in concave deformation

In order to study the influence of depth-thickness ratio on bedding slope stability, whose sliding surface is flexural concave in shape under mining conditions, this paper aims to study the characteristics ofdeformarion and damage of bedding sliding with depth-thickness ratios of 200：1,150：1,120：1,100：1 and 50：1 by adopting numerical simulation analysis software combined with laboratory-made ＂under the influence of mining variable sliding surface slope similar simulation test bed＂, and to propose identification methods for slope stability under the infuence of mining. The results show that mining activities under the slope reduce slope stability. With a decrease in the mining depth ratio, the influence of mining on the slope increases gradually, and the damage to the slope gradually expands, the stability of the slope grad- ually reduces, fracture occurs on the slope toe and the central fissure gradually develops to the surface, and reaches slide threshold when the depth-thickness ratio is 50：1.

Effect of the inclined weak interlayers on the rainfall response of a bedded rock slope

Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at various levels of depth below the surface on the variation of displacements and stresses in bedded rock slopes, four geo- mechanical model tests with artificial rainfall have been conducted. Displacements, water content as well as earth pressure in the model were monitored by means of various FBG （Fiber Bragg Grating） sensors. The results showed that the amount of displacement of a slope with a weak interlayer is 2.8 to 6.2 times larger than that of a slope without a weak interlayer during one rainfall event. Furthermore, the position of the weak interlayer in terms of depth below the surface has a significant effect on the zone of deformation in the model. In the slope with a high position weak interlayer, the recorded deformation was larger in the superficial layer of the model and smaller in the frontal portion than in the slope with a low position weak interlayer. The slope with two weak interlayers has the largest deformation at all locations of all test slopes. The slope without a weak interlayer was only saturated in its superficial layer, while the displacement decreased with depth. That was different from all slopes with a weak interlayer in which the largest displacement shifted from the superficial layer to the weak interlayer when rainfall persisted. Plastic deformation of the weak interlayer promoted the formation of cracks which caused more water to flow into the slope, thus causing larger deformation in the slope with weak interlayers. In addition, the slide thrust pressure showed a vibration phenomenon o.5 to 1 hour ahead of an abrupt increase of the deformation, which was interpreted as a predictor for rainfall-induced failure of bedded rock slopes.

Effect of buried plates on scour profiles downstream of hydraulic jump in open channels with horizontal and reverse bed slopes

Local scour downstream of sluice gates in erosive beds is one of the main concerns of hydraulic engineers because it can cause considerable damage to structures.Many researchers have conducted various studies to predict the maximum depth and length of scour holes and to develop new methods to control this phenomenon.In the methods that have recently been examined,embedded buried plates are used to control the scour in the erosive beds.In this study,using a physical model,the effect of buried plates in erosive beds on the depth of scour downstream of a hydraulic jump was studied.Several experiments were performed in which plates were buried at 50° and 90° angles at different distances from the apron in open channels with horizontal and reverse bed slopes.The results of experiments in which the scour profiles were drawn in dimensionless forms show that the angle and position of the plates are important to controlling and reducing scour depth.In fact,by reducing the angle of buried plates,the maximum depth of scour is also reduced.Also,comparison of the results of a single buried plate and double buried plates shows that using two buried plates at the distances of 30 and 45 cm from the non-erodible bed is more effective in reducing the scour depth.The best distances of the buried plates with angles of 90° and 50° from the non-erodible bed are 45 cm and 30 cm,respectively,in the condition with a single buried plate.

Physical Modeling of Landslide Mechanism in Oblique Thick-Bedded Rock Slope: A Case Study

The Jiweishan landslide illustrates the failure pattern of an apparent dip slide of an oblique thick-bedded rockslide. Centrifugal modeling was performed using a model slope consisting of four sets of joints to investigate the landslide initiation mechanism. Crack strain gauges pasted between the slide blocks and the base failed in sequence from the rear to the front as the centrifugal acceleration increased. When the acceleration reached 16.3g, the instantaneous failure of the key block in the front triggered the apparent dip slide of all blocks. The physical modeling results and previous studies suggest that the strength reduction in the weak layer and the failure of the key block are the main reasons for the Jiweishan landslide. The centrifuge experiment validated the previously proposed driving-blocks-key-block model of apparent dip slide in oblique with inclined bedding rock slopes. In addition, the results from limit equilibrium method and centrifuge test suggest that even though the failure of the key block in the front is instantaneous, a progressive stable-unstable transition exists.

Dynamic damage evolution of bank slopes with serrated structural planes considering the deteriorated rock mass and frequent reservoirinduced earthquakes

To investigate the dynamic damage evolution characteristics of bank slopes with serrated structural planes,the shaking table model test and the numerical simulation were utilized.The main findings indicate that under continuous seismic loads,the deformation of the bank slope increased,particularly around the hydro-fluctuation belt,accompanying by the pore water pressure rising.The soil pressure increased and then decreased showed dynamic variation characteristics.As the undulation angle of the serrated structural planes increased(30°, 45°, and 60°),the failure modes were climbing,climbinggnawing,and gnawing respectively.The first-order natural frequency was used to calculate the damage degree(Dd)of the bank slope.During microseisms and small earthquakes,it was discovered that the evolution of Dd followed the“S”shape,which was fitted by a logic function.Additionally,the quadratic function was used to fit the Dd during moderately strong earthquakes.Through the numerical simulation,the variation characteristics of safety factors(Sf)for slopes with serrated structural planes and slopes with straight structural planes were compared.Under continuous seismic loads,the Sf of slopes with straight structural planes reduce stalely,whereas the Sf for slopes with serrated structural planes was greater than the former and the reduction rate was increasing.

风荷载和列车共同作用下风积沙包芯路基边坡稳定性研究

我国是世界上沙漠分布最多的国家之一,沙漠中蕴藏着丰富的矿产资源。西部大开发和“一带一路”倡议将进一步推进沙漠地区铁路建设。利用丰富的沙漠风积沙作为铁路路基填料具有重要的经济意义和推广应用前景,风积沙包芯路基是一种充分利用风积沙作为铁路路堤填料的新型结构。为研究列车荷载和风荷载共同作用下风积沙包芯路基边坡稳定性计算方法,基于折线滑动法原理,对路堤结构进行分层分区,采用极限平衡方法,推导出列车荷载和沙漠风荷载共同作用下铁路风积沙包芯路基的稳定性系数计算公式并编制计算程序。结合和若铁路风积沙包芯路基的工程实例,验证了该计算方法的可行性。基于该计算程序,研究了风荷载大小、风向角、路堤填筑高度、填料内摩擦角等影响因素对风积沙包芯路基边坡稳定性系数的影响,分析了风向角、填料内摩擦角等影响因素对风积沙包芯路基边坡砂卵石封层最小厚度的影响。计算结果表明,风积沙包芯路基边坡稳定性系数与风荷载大小近似呈线性负相关,与风向角大小呈非线性正相关。风积沙包芯路基边坡稳定性系数富余量与路堤填筑高度呈负相关。风积沙包芯路基边坡砂卵石封层最小厚度与风向角大小呈非线性负相关,与风积沙填料的内摩擦角大小近似呈线性负相关。建议风积沙包芯路基边坡设计中应考虑风荷载的影响。研究成果可供沙漠地区风积沙包芯路基设计借鉴和采用。

含建筑桩基的顺层岩质边坡桩锚支护体系振动台模型试验研究

基于Bockinghamπ定理,对具有建筑桩基的顺层岩质边坡桩锚支护体系开展振动台模型试验,通过分析预应力锚索、建筑桩基的应变以及边坡坡顶加速度,研究支护体系的动力响应规律。结果表明,预应力锚索的应变在地震波加速度达到峰值时达到最大值,且上排锚索受力大于下排锚索,随着地震幅值的增大,最上排锚索锚固段率先发生滑移破坏失去锚固作用;建筑桩基应变最大值点位于滑动面以下一定深度,且远离边坡坡面的建筑桩基受力大于邻近边坡坡面的建筑桩基;坡顶各点峰值加速度随地震波幅值增大整体表现为线性增大,但在Wenchuan-Wolong波(0.55g)和Sin波(0.4g)工况时,各点峰值加速度相对有所下降,随着地震波幅值增大,各点峰值加速度放大系数在汶川波和正弦波作用下并非单调变化,而是表现为先减小后增大波动变化特点。

库区浮泥层纵向流速垂线分布特性研究

水库浮泥是存在于水库底部的一层高含沙水体,流动性较强,直接影响水库淤积形态和水库排沙,研究其运动规律对水库减淤优化调度具有重要意义。根据三峡库区实测泥沙矿物组成和级配资料,配置沙样进行流变试验,以幂律流变模型描述浮泥的本构关系。构建了浮泥运动的速度分布理论模型,通过水槽试验对模型进行了验证,计算结果与试验结果吻合较好。结果表明,浮泥运动速度随浮泥厚度、上层水流流速、床面坡度增大而增大,随浮泥密度增大而减少。沿水深方向浮泥纵向流速分布始终呈抛物线型,表层的浮泥流速要远大于底层浮泥,浮泥纵向流速沿垂向方向不断减少,最底部的浮泥几乎处于静止状态。

含软弱夹层顺层岩质边坡开挖稳定性分析

以都安高速公路某段含软弱夹层顺层岩质边坡为例,采用极限平衡法对开挖后的边坡进行稳定性分析,基于FLAC3D软件模拟分析边坡分级开挖、分级支护过程中的位移、最大剪切应变增量、应力特征及抗滑桩的承载性能。结果表明:严格条分法的安全系数为1.011,强度折减法安全系数为条分法的97.13%,当考虑岩土体变形时,传统计算方法可能会高估边坡自身的稳定性;边坡采用抗滑桩+框架锚索+框架锚杆的联合支护方式,并进行分步开挖及分级支护,对坡体扰动小,支护效果良好,能很好地控制坡体变形,避免边坡因软弱夹层塑性区贯通而发生失稳破坏。

古建筑压煤开采对斜坡上覆堆积层变形扰动影响研究

针对缓倾顺层斜坡上覆堆积层的采动稳定性与变形机理的研究,特别是从协调地下资源开采与地上文物古建筑安全防护视角出发的研究处在探索阶段。以山西省宝应寺斜坡堆积层为研究对象,基于地表动态监测与地质过程机制分析,结合数值模拟研究了堆积层稳定性与地表裂缝成因机制,并探讨优化了开采方式。研究表明:①长壁式地下开采是引起堆积层变形的诱因,堆积层软弱特性与斜坡软硬互层结构是其变形内因。堆积层下伏基岩变形模式为垂向挤压水平拉张,对堆积层变形具有放大效果,牵动其产生地裂缝。堆积层变形破坏机制为:坡下采空—覆岩弯曲—侧岩倾倒变形—下伏岩层应力集中—牵动拉裂;②堆积层裂缝分布在上坡方向采空区工作面端部附近,平面上近似平行,呈“之”字或锯齿状。地物裂缝较之地表裂缝数量更多、但规模更小,寺院建筑群受隐伏张性地裂缝影响致地基形变造成地面以上结构开裂;停采后监测期内,堆积体变形速率趋于收敛,残余变形消减,由变形移动转为基本稳定;③完全采空后,堆积层表现为以下错为主的拉张变形,剪应变显现,持续开采条件下堆积层变形程度将加剧。下伏基岩最大主应力增量达1080.75%,拉应力集中;④短壁房式开采留设区段煤柱利于减小堆积层变形。研究为认识地下资源开采扰动斜坡上覆堆积层变形破坏与寻求古建筑压煤开采文物保护解决方案提供了参考。

降雨开挖诱发顺层岩质滑坡稳定性与堆积特征

在自然环境与工程建设中,顺层岩质滑坡因其易发、频发、突发等特征,一直是地质灾害领域研究热点之一。以湖北省建始县大包山滑坡为例,综合现场调查、无人机(UAV)摄影等手段,开展含软弱夹层结构面强度弱化规律试验,考虑强度弱化的降雨-开挖联合作用,进行边坡动态稳定性与堆积特征数值模拟分析,探讨边坡破坏诱因,揭示边坡变形机制。主要结论如下:①自然边坡在天然、暴雨工况下稳定性系数分别为1.35和1.20,开挖边坡在天然、暴雨工况下稳定性系数分别为1.04和0.90;最不利工况下,边坡第四级开挖后,发生失稳破坏,诱因为降雨-开挖联合作用;②大包山滑坡破坏模式为典型的滑移-拉裂破坏,即滑坡体前缘侧向隆起,中后缘牵引式滑动,后缘发生拉裂破坏,滑坡体沿软弱结构面整体性顺层平面滑动;③大包山滑坡的变形破坏和启滑运动堆积过程可划分为5个阶段,即裂缝发展贯通阶段、启滑动态响应阶段、整体高速滑动阶段、平台碰撞制动阶段、堆积侧向挤滑阶段;滑坡前缘于坡脚处堆积,堆积距离约15~25 m,整体滑移水平距离约15 m,滑坡最大位移量高达30 m。研究成果对类似顺层岩质滑坡研究具有一定参考价值。

山区公路顺层边坡首次失稳长度影响因素及确定方法

西部山区公路建设中常遭遇顺层边坡,其首次失稳长度L_(c)是失稳机制及加固设计的关键参数,现有L_(c)确定方法存在一定局限性。依托31个四川盆周山区公路顺层边坡失稳案例,系统调查坡体结构特征(岩层倾角α、边坡走向与岩层走向的夹角θ和坡长L)及外在灾变诱因(切层厚度D和降雨量Q)对首次失稳长度的特征,并结合数值分析,探讨顺层边坡首次失稳长度的主要影响因子及确定方法,建立更加完善的多因素首次失稳长度的拟合关系式。结果表明:顺层边坡破坏主要发生在θ≤30°范围,坡体双面临空甚至三面临空时,θ>30°的顺层边坡也发生失稳;L_(c)随L的增大而增大,且L_(c)/L等于0.3~1.0;L_(c)/D介于3~24之间,不含软弱夹层时L_(c)/D等于3~10;α在12°~35°时,顺层边坡稳定性最差,且L_(c)/D随α的增大而减小;降雨对顺层边坡的失稳诱发源于软弱夹层的饱水软化,汛期开挖是含软弱夹层顺层边坡失稳的灾变诱因。边坡首次失稳长度影响因子敏感度从大到小排序为:①含软弱夹层边坡:岩层倾角、坡长、切层厚度、内摩擦角、黏聚力、弹性模量、开挖高度;②无软弱夹层边坡:岩层倾角、内摩擦角、切层厚度、黏聚力、坡长。提出的走向夹角折减系数和多因素首次失稳长度计算公式对边坡破坏范围的确定有指导意义。

软弱结构面参数对顺层岩质边坡动力响应的影响研究

为了探究地震作用下软弱结构面对岩质边坡动力响应特征的影响。以云南省某露天矿山边坡为研究背景,利用有限差分软件中的非线性动力分析法对顺层岩质边坡进行动力计算,通过控制变量法设计了一系列的数值实验,探究了软弱结构面参数的改变对岩质边坡动力响应的影响规律,再基于正交试验以及极差分析法对影响岩质边坡动力响应的结构面参数进行了敏感性分析。结果表明:结构面参数的改变对于顺层边坡的动力响应有较大影响;各影响因子对顺层岩质边坡动力响应影响程度大小排序为结构面黏聚力>结构面倾角>结构面内摩擦角>结构面厚度。动力响应的研究可为地处地震频发区域的顺层岩质边坡提供抗震依据。

珠海市南水镇金龙边坡变形破坏特征及稳定性评价

边坡稳定性分析评价是边坡调查评价过程中一个不可或缺的环节。以珠海市金龙边坡为研究对象,分析了边坡的发育特征、影响因素、形成机制。在查明边坡岩土体出露及结构特征基础上,根据典型断面C、ϕ值反演分析及敏感性分析结果,确定金龙边坡岩土体物理力学参数,采用极限平衡法对金龙边坡进行稳定性分析评价。评价结果表明:金龙边坡在天然工况下处于欠稳定状态,在饱和及饱和+地震工况下处于不稳定状态。