资兴高速K21段顺层岩质边坡支护过程数值模拟研究

以资兴高速K21段顺层岩质边坡为研究对象,借助现场调查、数值模拟研究段边坡的开挖和支护过程,对各阶段的稳定性、位移、应力等的变化规律进行分析,验证了开挖、支护设计的合理性以及边坡加固的安全性,研究了边坡在开挖支护过程中应力应变规律。结果表明,顺层岩质边坡开挖扰动开挖破坏了边坡原有的应力分布,导致岩体产生裂隙损伤和变形,并逐渐扩张,弱化岩体和层面自身的强度。同时,边坡开挖,直接破坏了边坡原有的连续受力体系,由于软弱层面的抗剪强度较低,从而导致岩层沿开挖揭露的软弱层面整体下滑。锚索框架一方面通过对坡体的位移的控制作用,增加坡体的稳定性,另一方面通过预应力锚索把层状岩体锚固在一起,使得各层之间摩阻力增大,内应力和挠度大为减少,大大提高了层面的抗剪强度。     

破碎性地层概念界定及其破碎的热力学分析

借助于岩土工程、岩土力学、岩石力学、土木工程等学科,提出了破碎、破碎体（破碎性地层）概念。阐述了这类岩体的破坏方式、破坏的失稳类型。根据热力学定律和微观结构观点,岩体破碎过程实质上是一种内能耗散现象,破碎的发生意味着要耗散一部分能量去产生新的裂纹面。给出了破碎性地层的稳定准则,可用以确定裂纹的稳定状态。当裂纹失稳时,裂纹会向前扩展演化,产生新的裂纹,到一定程度后,将会导致岩体破碎。     

开挖与卸载交替作用对上陡下缓型高陡层状岩质边坡变形失稳影响试验研究(“第六届水利水电岩土力学与工程学术研讨会”推荐稿件)

上陡下缓型高陡层状岩质边坡在我国西部地区典型发育,开挖与卸载交替作用对其变形失稳破坏具有非常重要的影响。以云南磷化集团有限公司所属尖山磷矿上陡下缓型高陡层状岩质边坡为工程背景,依据相似理论开展了模型试验研究,分析开挖与卸载交替作用对这类型岩质边坡变形失稳的影响。结果表明：上陡下缓型高陡层状岩质边坡随开挖深度的逐渐增加,其对应的位移变形量也逐步变大,边坡整体上表现为上部向下运动,下部受压向临空面方向隆起的变形规律,同时当开挖至一定的深度后,坡面与坡中均会发育较多的走向裂缝,且随着开挖深度的不断增加,其不断向坡体深部延伸发展;在整个开挖过程中,坡体中会发育形成“平面与圆弧面复合型”类型的潜在最危险滑移面,且表现为“滑移-弯曲-剪切”的变形失稳破坏特征;对边坡开展的浅部卸载作用效果不理想,虽其位移变形量有所减小,但没改变坡体整体的变形失稳趋势,然对边坡施加的深部卸载作用效果非常明显,使坡面及坡顶产生的裂缝几乎完全消除。研究结果可为我国西部大开发过程中面临的上陡下缓型高陡层状岩质边坡的预警预报与治理设计提供参考。     

断续节理岩体中围岩破裂区的试验研究

为了研究断续节理对围岩破裂区形成与扩展以及破裂区大小的影响,采用真三轴巷道平面应变模型试验台,运用数字照相进行变形量测的方法,研究分析了断续节理岩体中裂纹的产生、扩展与贯通机理及其围岩的破坏失稳行为．结果表明：在断续节理岩体中,围岩破裂区是由于新生裂纹与原有节理相互贯通,导致岩体中产生纵横交错的贯通裂隙所致;在断续节理的影响下,巷道围岩破裂区并不是均匀发展,而是首先产生于顶板节理附近,然后向巷道周边其它相邻部位发展;最终的破裂区厚度在平行于节理方向最大,而在垂直于节理方向的厚度最小．     

流固耦合作用下节理岩质边坡失稳过程的RFPA模拟分析

利用基于强度折减法的RFPA-Slope对渗流与应力耦合作用下的软弱互层岩质边坡稳定性进行了数值模拟分析,数值模拟不但直观形象地给出了边坡的渗流场、应力场、破坏区分布,而且得到了边坡滑移破坏面的萌生、扩展、贯通以及坡体整体失稳的渐进破坏过程,同时求得安全系数。并与无地下水的稳定性作了比较,结果表明,地下水渗流的作用使坡体位移增大,边坡安全系数减小,明显加大了滑坡范围。对实例的分析说明,RFPA-Slope能够较为准确地预测边坡潜在破坏面的形状与位置及计算相应的稳定安全系数,本文方法对于边坡,特别是对于复杂边坡的稳定性分析具有实用性。     

库区公路倾倒岩体边坡高位错落变形机理及治理措施

倾倒岩体边坡是岩体向临空面发生弯曲变形的特殊岩质边坡，随着边坡开挖岩体卸荷，坡体应力重新分布，倾倒岩体折断面逐渐连通，坡体持续发生时效变形，易导致边坡变形失稳。依托澜沧江苗尾库区沿江公路倾倒岩体边坡实例工程，分析边坡高位错落变形特征及孕育过程，研究倾倒岩体边坡高位错落变形影响因素、失稳原因及变形机理；边坡治理遵循“锁口、强腰、固脚”的思路，采用削坡减载、主动预加固防护、挂网喷锚、堆渣压坡及截排水措施等进行综合治理，评价边坡加固前后的稳定性。结果表明：倾倒岩体边坡变形具有继承性，高位错落变形是前期倾倒岩体变形的延续；倾倒岩体变形边坡治理以主动预加固防护为主，削坡减载与锚固防护并重，限制倾倒变形岩体应力松弛与蠕变，可为类似边坡病害分析与治理提供借鉴和参考。     

基于DIC技术的充填体固结时间对花岗岩裂纹扩展的影响研究

为了研究地下工程中裂隙岩体的变形、破坏规律对岩体稳定性控制的影响,基于数字图像相关方法,对单轴压缩下未充填裂隙岩石、充填裂隙岩石的应变场演化过程进行监测,结合滑动裂纹模型理论,从宏观和细观角度系统地分析了裂隙岩石在破坏过程中的裂纹萌生、扩展和贯通规律。结果表明:未充填裂隙岩石应变场内最大应变值主要集中于两预制裂隙尖端连接处,沿预制裂隙某一侧贯通破坏,而充填裂隙岩石应变场内最大应变值主要集中于两预制裂隙连接处与次翼裂纹扩展处,沿预制裂隙两侧贯通破坏;未充填裂隙岩石的岩桥边界区域以剪切破坏为主,充填裂隙岩石的岩桥区域以张拉破坏为主,无论裂隙岩石充填与否,应变场内都主要分为拉应力与压应力区域;在弹性阶段内,应变场中已形成了沿翼裂纹、次翼裂纹扩展路径的局部化应变带;在内侧翼裂纹和次翼裂纹的搭接处,破坏程度最严重。随着充填体固结时间的延长,在预制裂隙尖端处,伴有剪切起裂的次生共面裂纹扩展,所形成的断面粗糙度高于其他断面。     

开挖与卸载交替作用对上陡下缓型高陡层状岩质边坡变形失稳影响试验研究

以云南磷化集团有限公司所属尖山磷矿上陡下缓型高陡层状岩质边坡为工程背景,依据相似理论开展模型试验研究,分析开挖与卸载交替作用对这类型岩质边坡变形失稳的影响。结果表明:上陡下缓型高陡层状岩质边坡随开挖深度的逐渐增加,其对应的位移变形量也逐步变大,边坡整体上表现为上部向下运动,下部受压向临空面方向隆起的变形规律;同时当开挖至一定的深度后,坡面与坡中均会发育较多的走向裂缝,且随着开挖深度的不断增加,其不断向坡体深部延伸发展。在整个开挖过程中,坡体中会发育形成"平面与圆弧面复合型的潜在最危险滑移面,且表现为滑移-弯曲-剪切的变形失稳破坏特征。对边坡开展的浅部卸载作用效果不理想,虽其位移变形量有所减小,但没有改变坡体整体的变形失稳趋势,对边坡施加的深部卸载作用效果非常明显,使坡面及坡顶产生的裂缝几乎完全消除。研究结果可为中国西部大开发过程中面临的上陡下缓型高陡层状岩质边坡的预警预报与治理设计提供参考。     

不同倾角裂隙砂岩单轴压缩颗粒流模拟分析

为探索不同倾角裂隙岩体在单轴压缩作用下的破坏形式,利用二维颗粒流程序(PFC2D)对不同倾角裂隙岩体试样进行单轴压缩数值模拟,研究了不同倾角裂隙岩体的强度变化规律、破坏形式以及裂纹扩展路径。结果表明:不同倾角预制裂隙岩体的破坏模式略有不同;不同倾角预制裂隙岩体破坏过程基本一致,都会经历弹性变形阶段、裂纹稳定扩展阶段、岩体失稳阶段3个阶段;不同倾角裂隙的存在使得岩体的抗压强度有不同程度的降低;在单轴压缩破坏中,裂隙的顶点应力集中现象比较严重,沿裂隙岩体对角线方向产生的裂纹最多。该数值模拟分析为进一步探索地下工程中裂隙岩体失稳破坏规律提供了参考。     

基于离心模型试验的岩质边坡敏感性研究

根据相似理论制作了均质岩质边坡模型,通过离心机增加边坡坡体容重再现边坡失稳过程,并对全长粘结锚杆应力进行监测来研究均质岩质边坡在不同加速度作用下的内部应力场变化规律、边坡破坏形式,并预测锚杆监测最佳位置。研究结果表明,在离心机分级加速过程中,各锚杆应力监测点应力曲线呈阶梯式增长趋势,且各监测点在700 s左右曲线出现反弯点,应力监测比位移监测提前;边坡破坏过程中,坡顶易出现拉裂缝,坡脚处易发生压剪破坏;在实际边坡稳定性监测中,宜选择坡脚附近的潜在滑动面处作为监测点。     

裂隙及卸荷对岩体边坡的影响

应用弹塑性力学及断裂力学的相关理论,分析讨论了裂纹的分形特性及裂隙面的压剪起裂破坏机理;分析了静载、动载和不同类型裂隙的相互作用对边坡稳定性的影响规律。结合工程实际问题,研究了边坡开挖前后其应力应变的分布规律,提出了由于开挖卸荷而引起裂纹扩展的作用机理。     

Mechanism of action of cracks water on rock landslide in rainfall

In worldwide, the most common triggering factor of rock landslides is extended and intense rainfall. However, different from the soil slope failure caused by softening action of infiltration rainwater, the mechanism of rock landslide in rainfall is not clear. From the view of fracture mechanics, the propagation of cracks on rock slope and the development of sliding surface were researched. Then based on hydraulics formulas and using Sweden arc method, the influence of crack water on stability of rock slope was quantitatively studied. Finally, an example was given to check the theoretical approach. The result shows that the development of sliding surface of rock slope is mainly caused by crack propagation under hydrostatic pressure when the stress intensity factor K _I at crack tip is bigger than the toughness index of rock fractures K _IC, and the failure of slope is the result of hydraulic action of crack water and the softening of materials on sliding surface when the depth of crack water is bigger than a minimum value h _min.     

锦屏一级水电站左岸边坡高地应力区卸荷松弛特征及其控制措施

岩体开挖卸荷松弛效应对边坡的稳定性影响巨大,如何控制岩体卸荷松弛程度非常重要。以锦屏一级水电站左岸高边坡为研究对象,区域3维地应力场反分析结果表明:工程区域内地应力水平较高,水平构造应力较大,河床处的最大主应力达到40～50 MPa。施工期声波波速及钻孔变模的测试数据表明:边坡高地应力区的岩体卸荷松弛现象非常明显,岩体卸荷松弛深度随着地应力的增大而增大。边坡高地应力区开展的先挖后锚和先锚后挖的两种岩体卸荷松弛控制试验表明:先锚后挖能够有效地改善岩体的应力释放,同时能够较好地控制岩体的变形。     

岩石卸荷破坏与岩爆效应

对粉砂岩试样进行了保持轴向变形不变的卸围压试验,在对岩样的破坏分析基础上,将岩石卸荷破坏与岩爆特征联系起来.研究表明,随着卸荷初始围压值的增加,卸荷破坏状态逐渐从中等岩爆过渡到强烈以上岩爆;三轴应力状态下的岩体如果某一方向的应力突然降低,造成其在较低应力状态下破坏,那么原岩储存的弹性应变能将对外释放,进而可能引起岩爆;通过调整施工速度可以减缓或降低岩爆的发生.     

Failure behavior of a rock-coal-rock combined body with a weak coal interlayer

Using an MTS 815 testing machine, the deformation and failure behavior of a rock-coal-rock combined body containing a weak coal interlayer has been investigated and described in this paper. Uniaxial loading leads to the appearance of mixed cracks in the coal body which induce instability and lead to bursts in coal. If the mixed crack propagates at a sufficiently high speed to carry enough energy to damage the roof rock, then coal and rock bursts may occur – this is the main mechanism whereby coal bumps or coal and rock bursts occur after excavation unloading. With increasing confining pressure, the failure strength of a rock-coal-rock combined body gradually increases, and the failure mechanism of the coal interlayer also changes, from mixed crack damage under low confining pressures, to parallel crack damage under medium confining pressures, and finally to single shear crack damage or integral mixed section damage under high confining pressures. In general, it is shown that a weak coal interlayer changes the form of overall coal damage in a rock-coal-rock combined body and reduces the overall stability of a coal body. Therefore, the whole failure behavior of a rock-coal-rock combined body in large cutting height working faces is controlled by these mechanisms.     

Research on Mechanism of Rock Burst Generation and Development for High Stress Rock Tunnels

Through the investigation and analysis of high stress distribution in surrounding rock during the excavation of rock tunnels,the key factors to cause rock burst and the mechanism of rock burst generation and development are researched. The result shows that the scale and range of rock burst are related with elastic deformation energy storied in rock mass and the characteristics of unloading stress waves. The measures of preventing from rock burst for high stress rock tunnels are put forward.     

边坡工程中卸荷岩体的探讨

岩体卸荷是水利水电工程建设中常见的工程地质问题,岩体卸荷裂隙是影响边坡岩体稳定性的重要因素.文章介绍了边坡工程中卸荷岩体的形成机理、裂隙类型、分带依据及卸荷岩体加固时应注意的问题.     

Numerical Simulation of Rock Burst in Circular Tunnels Under Unloading Conditions

Rock burst in a circular tunnel under high in-situ stress conditions was investigated with a numerical method coupled the rock failure process theory (RFPA) and discontinuous deformation theory (DDA).Some numerical tests were carraied out to investigate the failuer patterns of circular tunnel under unloading conditions.Compared the results under loading conditions, the shapes of failure zones are more regular under the unloading conditions.The failure patterns in the same type of rock mass are clearly different because of non-homogeneity of the rock material.The extension of cracks shows some predictability with an increasing of in-situ stress.When the homogeneity index of rocks (m) is either relatively high or low and lateral pressure coefficients (λ) is high, the number of regular shear slide cracks decreases and the probability of a rock burst also becomes lower.Our numerical simulation results show that the stability of surface rock and the natural bedding stratification of rock material greatly affect rock bursts.Installing bolts with due diligence and suitably can effectively prevent rock bursts.However, it is not effective to control rock bursts by releasing the strain energy with normal pre-boreholes.     

Mechanical behavior of coal under different mining rates: A case study from laboratory experiments to field testing

During deep mining, the excavation disturbance stress path is the domination factor for the stability of the surrounding rock mass as well as the ground pressure. One of the important parameters of the stress path is the loading or unloading rate of the disturbed rock or coal, which depended on the mining rate. To achieve a well understanding of the mining rate and its effect on the coal behavior, a preliminary case investigation of the mechanical properties of the coal at the various mining rates in both the laboratory scale and field scale was performed. Based on the uniaxial compression test and the digital image correlation(DIC) method, the mechanical behavior of the coal samples, such as the evolution of the strength,surface deformation, crack propagation, and elastic strain energy of the coal under the various loading rates were analyzed. A threshold range of the loading rate has been observed. The uniaxial compressive strength(UCS) and releasable elastic strain energy(Ue) increase with increasing loading rate when the loading rate is below the threshold. Otherwise, the UCS and Uemay decrease with the loading rate.Under the low loading rate( 0.05 mm/min), the tensile deformation of the original defects could result in crack coalescence, whereas failure of the coal matrix is the key contributor to the crack coalescence under the high loading rate(greater than 0.05 mm/min). Afterwards, with the consideration of the bearing capacity(UCS) and energy release of the mining-disturbed coal mass(Ue), a power exponential relationship between the mining rate(MR) in the field and the critical loading rate(vc) in the laboratory was proposed. The application potential of the formulas was then validated against the field monitored data.Finally, based on the critical loading rate, the released strain energy, and the monitored pressure on the roof supports, a reasonable mining rate MRfor the Ji 15-31030 working face was determined to be approximately 3 m/d.     

开挖卸荷条件下边坡的变形分析

岩体工程具有加载和卸荷两种不同的力学状态,在此力学形态各异的情况下,岩体的力学特性有本质区别.岩石边坡开挖为卸荷力学条件,运用加载的力学理论和方法研究卸荷岩体的变形,往往与实际有较大的出入;采用卸荷岩体力学的方法分析边坡的位移变形比较符合实际.