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.

Strength and deformation behaviors of bedded rock mass under bolt reinforcement

The mechanism of bolt support is an important topic in mining engineering and slope treatment. The artificial material and loading system were self-developed to study the influence of bedding cohesion and bolt number on the anchoring behavior of bedded rock mass. The results show that, both peak strength and elasticity modulus increase gradually with the increase of bedding cohesion and bolt number. The axial stress–strain curve of bedded rock mass under the reinforcement of bolts presents the features of strain-softening and secondary strengthening. Finally, anchoring behavior of bedded rock mass with different bolt numbers was simulated by using FLAC3 D numerical program and the results were compared with the experimental results. This study can provide certain bases to the stability control and support design of bedded rock mass in roadway.

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.

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 geomechanical 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 thesuperficial 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 0.5 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.

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.

Quality index of bedded and joint-bearing rock mass and its applications

Based on the theory of Fuzzy Mathematics and Expert System, this paper presents the quantitative expression method of bedded and joint bearing rock mass quality "Stratum Quality Index"(SQI for short), and also introduces the successful application of the method in estimating stratum movement parameters.

各向异性层状千枚岩渗透率及有效孔隙率试验研究

采用岩石全自动三轴伺服仪和气体渗透装置,对一种致密的各向异性层状千枚岩开展了气体渗透率及有效孔隙率试验,研究常规三轴压缩和围压循环加卸载2种应力路径下,气体渗透率、有效孔隙率随层理倾角及偏应力的演化规律。结果表明:围压相同时,岩样的初始气体渗透率k0随着层理倾角β的增大呈“W”型变化,在β=45°时取最大值;在围压循环加卸载过程中,气体渗透率先随围压的加载而减小,后随围压的卸载而增大,卸载时的气体渗透率小于加载时的渗透率;层状千枚岩有效孔隙率和气体渗透率呈指数关系;平行于层理方向的气体渗透率远大于垂直于层理方向的气体渗透率;岩样有效孔隙率和气体渗透率随偏应力变化经历初始压密阶段、线弹性阶段和塑性变形阶段,随着偏应力的增大,岩样有效孔隙率和气体渗透率先减小,接着保持稳定,最后快速增大,并在岩样应力-应变曲线斜率接近于0时达到最大值。

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。

Rock Pressure on Tunnel with Shallow Depth in Geologically Inclined Bedding Strata

The method to calculate rock pressure to which the lining structure of tunnel with shallow depth is subjected in geologically inclined bedding strata is analyzed and put forward. Both the inclination angle of bedding strata as well as the internal friction angle of bedding plane and its cohesion all exert an influence upon the magnitude of the asymmetric rock pressure applied to tunnel. The feature that rock pressure applied to tunnel structure varies with the incUnation angle of bedding strata is discussed, At last, the safety factor, which is utilized to evaluate the working state of tunnel lining structure, is calculated for both symmetric and asymmetric lining structures. The calculation results elucidate that the asymmetric tunnel structure can be more superior to bear rock pressure in comparison with the symmetric one and should be adopted in engineering as far as possible.

中国大规模盐穴储氢需求与挑战

氢能是来源广泛且低碳清洁的能源,大力发展氢能产业是实现双碳目标和应对全球能源转型的重要举措。在氢能“制备―储存―运输―应用”全产业链中,储氢难问题长期制约着氢能产业高质量发展。盐穴储氢具有成本低、规模大、安全性高和储氢纯度高等突出优势,是未来氢能大规模储备的重要发展方向,也是我国能源低碳转型的重大战略需求。综合调研了我国制氢产业和氢能消费现状,分析了我国盐穴储氢的需求。调研了国外利用盐穴储存天然气和氢气的技术及工程现状,总结了我国盐穴储气库发展和建设历程。对比了利用盐穴储存天然气、氦气、压缩空气和氢气的异同点,提出我国盐穴储氢面临三大科技挑战:层状盐岩氢气渗透与生化反应、盐穴储氢库井筒完整性管控、储氢库群灾变孕育与防控。研究成果明确了我国氢气储备需求的快速增长趋势和大规模盐穴储氢的重点攻关方向。

层状岩石不排气三轴压缩力学特性试验研究

为研究地下隧洞开挖过程中围压和孔隙气压对层状千枚岩力学特性及变形参数的影响,以氩气作为渗透介质,开展层状千枚岩不排气三轴压缩试验,分析层状千枚岩在不同围压和孔压下应力-应变关系、峰值强度、变形特性及破坏形式随层理倾角的演化特征。引入基于层理倾角的各向异性度公式,探讨围压和孔压对层状千枚岩各向异性的影响。结果表明:不排气条件下,当孔压减小或围压增大时,层状千枚岩峰值强度逐渐增大;岩石峰值强度σc、弹性模量及变形模量随层理倾角的增大呈“U”型变化;层理倾角在30°~60°之间,层状千枚岩存在层理弱面,破坏形式主要为沿层理面剪切滑移破坏;层状千枚岩在平行层理方向受围压、孔压影响较大,呈现明显各向异性特征。

基于耗散能演化的层状黄砂岩损伤本构模型及其验证

层理构造影响工程岩体力学性质及稳定性.为探究层理倾角对岩石变形损伤过程的影响,开展了0°,15°,30°,45°,60°,75°,90°共7种不同层理角度的黄砂岩纵波波速测试和单轴压缩试验,分析了层理角度对黄砂岩峰值强度、弹性模量及破裂模式的影响,基于弹性模量劣化程度和耗散能演化特征分别表征黄砂岩初始层理损伤变量和荷载损伤变量,并借助Logistic函数模拟了层理与荷载耦合损伤变量演化全过程,探讨了层理角度对黄砂岩损伤演化规律的影响,进一步结合损伤力学理论与有效介质理论,建立了能够模拟单轴压缩下层状黄砂岩变形全过程的分段本构模型.结果表明:随层理倾角增大,黄砂岩纵波波速逐渐增大,峰值抗压强度和弹性模量呈现先减小后增大再减小的倒N型变化趋势,各向异性特性明显;黄砂岩破裂模式与层理倾角密切相关,倾角在0°~60°范围内时,主要发生穿切层理弱面的劈裂型张拉破坏,倾角为75°和90°时,岩样发生沿层理弱面的剪切滑移和劈裂张拉破坏;基于耗散能表征的损伤演化曲线可分为初始无损伤、损伤开始、损伤加速及损伤减速终止4个过程,借助Logistic函数构建的理论损伤模型可以很好的模拟和预测层状黄砂岩损伤演化全过程;初始层理损伤最大值与最小值之比约为1.41,表明层理倾角对黄砂岩初始损伤影响较大;建立的分段本构模型可以较好的描述层状黄砂岩单轴压缩应力–应变全过程,且理论模型曲线与试验数据吻合度高.

铁路道砟材质选型分析与建议

我国铁路覆盖范围广,沿线所处地质环境复杂、气候多变,铁路运维面临巨大挑战。有砟道床作为铁路重要组成部分,其养护维修一直以来倍受关注,然而,岩石材料具有多样性和分布不均衡性,且我国道砟材质标准及选型较为单一,并未考虑地质及气候环境等因素,给铁路建设及运维带来一系列问题。针对此,总结世界各国道砟选型方式及方法,对比复杂环境道砟材质选型标准,归纳新型道砟材料,并且解释了标准中用于道砟性能量化的指标及其试验方法。对比各国所道砟材质及其配套的选型标准,得到以下主要结论:(1)针对我国现有道砟规范问题,可以考虑根据铁路沿线地质和气候等因素选择道砟材质;(2)目前仍没有方法可以快速、准确并且不破坏道床的方式来得到道床堆积密度;(3)为实现双碳目标,在有条件的新建或改建线路上可考虑选用建筑固废、工业固废等新型道砟材料。

陕西省煤矿典型水灾隐患特征及治理技术

陕西省煤炭资源丰富,2022年煤炭产量达7.46亿t,是我国主要产煤省份之一。由于全省煤矿区地质及水文地质条件差异明显,煤矿水灾类型多样,随着近年煤炭开采强度的增大,水灾事故时有发生,防治水形势较为严峻。以煤炭赋存条件为基础,系统总结区域水文地质结构特征,界定典型水灾类型及各类水灾影响区域分布,论述典型水灾的形成机理及特征,并提出了相应的防控技术。研究表明:(1)陕西省主要煤炭产区分为陕北、黄陇、渭北三大区,陕北侏罗纪煤田主要有顶板松散沙层水灾隐患、厚层砂岩水灾隐患、溃水溃沙灾害,局部区域分布有烧变岩对煤矿造成水灾隐患;黄陇煤田主要受顶板巨厚砂岩水灾隐患、离层溃水隐患、泥砂溃涌灾害隐患威胁;陕北石炭—二叠纪煤田和渭北煤田,主要受到煤层底板奥陶系灰岩水灾隐患威胁。(2)陕北侏罗系煤田顶板水灾隐患主要为顶板含水层受开采导水裂隙带扰动形成,导水裂隙波及砂岩含水层或松散沙层可形成持续大流量涌水,部分区域充水强度较大,在短时间水量较大超过排水系统能力时造成顶板水灾,在薄基岩区域垮落带直接导通松散沙层时可转变为溃水溃沙灾害,导水裂隙带影响到烧变岩富水区域时可形成瞬时水量大且持续的烧变岩水灾;黄陇煤田顶板巨厚砂岩含水层受采动导水裂隙带波及形成高强度持续涌水并可能形成顶板水灾,当含水层下部隔水层厚度较大时,可能形成离层溃水灾害,当近煤层顶板岩层松软遇水易崩解时可转变为泥砂溃涌灾害;陕北石炭—二叠纪煤田和渭北煤田,煤层开采底板扰动破坏带或断层等构造导通奥陶系灰岩含水层时,会引发极为严重的底板突水灾害,该类灾害具突发性强、瞬时水量大的特征。(3)各区域的顶板水灾隐患治理技术主要包括钻孔疏泄、注浆治理、开采参数控制等,底板水灾隐患治理技术主要包括区域注浆加固及封堵等;烧变岩水灾隐患主要采取帷幕注浆与钻孔探放有机结合的防治技术。

顺层变质岩坡稳定性评价与生态治理方案

为了探究鄂西北变质岩区不稳定斜坡滑崩地质灾害的成因机制和生态治理模式,以三用塘顺层变质岩不稳定斜坡为研究对象,在查明灾害体地质与变形特征的基础上,分析了其可能的破坏模式与主要影响因素,深入探究了顺层变质岩坡渐进式变形破坏的成因机理。采用极限平衡等方法对不稳定斜坡进行了稳定性分析评价,结果表明,该斜坡体处于不稳定状态。基于地质灾害生态治理理念,提出了削方整形、护脚墙、格构锚固、截排水沟、生态绿化与监测等综合防治措施。通过工程实施及效果监测表明:该治理方案不仅有效地消除了三用塘滑崩地质灾害安全问题,而且取得了良好的环境绿化与美化效果。其综合防治措施,特别是将地质灾害防治与生态绿化融为一体的生态治理模式可为同类顺层变质岩不稳定斜坡的加固与坡面防护提供借鉴。

干湿循环作用下嵊州-新昌地区红层软岩崩解及强度弱化特性

红层软岩遇水易崩解并造成其强度弱化,在边坡工程建设中易造成其稳定性弱,导致经济损失,甚至人员伤亡。揭示红层软岩干湿循环作用下黏聚力与内摩擦角的变化特征对于针对性设计边坡处理措施具有重要意义。以浙江嵊州-新昌地区下白垩统朝川组3组红层软岩为研究对象,通过干湿循环试验、崩解岩块点荷载强度试验和崩解颗粒直剪试验研究了红层软岩崩解及强度弱化特性。结果表明:试样在干湿循环作用下呈碎块状-粒渣状-泥糊状依次崩解的形态,其主要崩解过程可分为初始崩解、快速崩解、细微再崩解和崩解稳定4个阶段;试样的点荷载强度I_(s(50))随干湿循环次数的增加而降低,耐崩解指数I_(dn)与点荷载强度I_(s(50))呈正指数关系,试样的点荷载强度I_(s(50))在耐崩解指数I_(dn)为80%~100%之间急速弱化,在耐崩解指数I_(dn)为50%~80%之间表现缓慢弱化特性;试样的峰值抗剪强度介于0.567~1.219 MPa之间,其多发生在剪切位移3 mm前后,同组试样在相同轴压下,峰值抗剪强度随循环次数的增加而减小,试样崩解颗粒内摩擦角在22.28°~33.03°之间,黏聚力在0.46~0.74 MPa之间。试样的摩擦角和黏聚力随着干湿循环次数增加,都呈负指数关系。试验结果表明砂质比泥质胶结的耐崩解性更好,黏土矿物高的岩石更容易崩解,而“白色矿物”钠长石的吸水膨胀能力远不及黏土矿物,其含量差异对耐崩解性的影响不及黏土矿物。

原生层理结构影响下煤岩组合体超声波及CT扫描分析

为研究原生层理结构对煤岩组合体波速及力学性质的影响,并提升室内获取煤岩波速及力学参数的精确性、快速性及便捷性,在室内对不同原生层理倾角的煤岩组合体开展了多层位多方位的超声波及CT扫描测试。基于超声波测试数据,获取了原生层理结构影响下煤岩组合体不同层位的波速及波速比变化特征;结合CT扫描及三维重构技术,应用煤岩灰度分布频数数据,提出了不同层位CT灰度均值的计算方法,获得了不同原生层理倾角下煤岩组合体不同层位灰度及煤岩含量的变化规律,建立了煤岩CT灰度均值与波速、力学参数的关系;构建了考虑层理倾角与煤岩含量效应的煤岩组合体纵波波速计算模型,并应用测试数据进行了对比验证。结果表明:①含原生层理的煤岩组合体波速及波速比与层理倾角线性相关,随层理倾角增加,组合体的纵波波速近似线性减小,而波速比的分布范围增大;②不同层理倾角下组合体的CT灰度均值与波速线性相关,随CT灰度均值增高,煤岩组合体波速线性增加;③煤岩组合体的密度随CT灰度均值增加线性增高,其动态弹性模量及剪切模量则与CT灰度均值均呈三阶多项式关系,并随CT灰度均值增高趋于增大;④层理倾角与煤岩含量相比,组合体波速对煤岩含量的敏感性更高,煤岩含量相近则波速受层理倾角响变化最大。

间歇式降雨对沅麻盆地红层滑坡的影响分析

沅麻盆地红层边坡具有岩层倾角小和所处边坡坡角小的特点,天然状态下处于相对稳定状态。水对红砂岩的力学性质有着很大的影响,降雨的入渗会引起边坡内土层饱和重度上升和基质吸力下降,在裂隙中产生的水头会对坡体有平推力。为了研究降雨对边坡稳定性的时间-空间效应,通过现场勘察沅麻盆地地区已有滑坡,采取数值模拟等手段进行定性和定量分析,还原大华坪滑坡的全过程,并对不同强度下前期降雨和后期降雨对边坡的作用进行对比分析。结果表明:前期降雨影响体现在入渗后引起的基质吸力降低和裂隙中水压不断上升,安全系数不断下降但未能达到滑坡临界值,停雨后边坡安全系数的回升具有滞后性,前期降雨量越小滞后性越明显;后期降雨影响体现在降雨量越大,更容易形成表面渗流,增大了下滑力。如果原有裂隙中存在积水,则坡体停雨阶段的安全系数变化比较缓慢。

红层软岩隧洞围岩稳定性分析及分类方法改进

以亭子口灌区一期工程(Ⅳ标段)为工程实例,选取小洞径隧洞较典型的工程地质条件类型,运用工程地质分类法、RMR法、Q系统围岩分类方法分别对红层软岩隧洞围岩稳定性进行分类,由此避免因单一方法造成的系统偏差,对本工程隧洞围岩有了更系统的认识,评价了各方法适用性,并指出各方法分类过程中侧重的分类指标及存在的问题。为改进工程地质分类方法并建立本项目专门的围岩分类方法提供了技术参考和思路:(1)对于小洞径完整软岩岩石强度指标权重可适当降低;(2)对于无结构面发育的围岩,其结构面产状与洞向组合关系指标减分项数值可适当缩小;(3)对本工程水理性质敏感的软岩,因围岩干燥状态和遇水后的工程性质差异巨大,工程地质分类法低估了软岩有水后的劣化影响,故地下水指标权重可适当增大;(4)洞径的影响可加入评分系统中,以某一标准洞径作为零分项,超出该洞径范围实行加、减分。按照以上思路改进工程地质分类对规范的修订有较高参考价值。