Interaction between tunnel and unstable slope – Influence of time-dependent behavior of a tunnel excavation in a deep-seated gravitational slope deformation

A back analysis of old tunnels in an unstable slope context leads to consider several situations of tunnel entering a slope: cross-cutting tunnel to the slope, oblique tunnel to the slope, or shallow tunnel parallel to the slope. Identified pathologies of structures vary depending on these situations. In the context of a shallow tunnel, the tunnel excavation leads to a slope destabilization due to a more or less important deconfinement of the surrounding massif. Construction techniques influence, on one hand, slope surface displacement acceleration, on the other hand, structural damages in the tunnel lining. Nevertheless, the interaction between tunnel and unstable slope depends on the distance between the slope surface and the tunnel lining plot according to the tunnel diameter (D) and on the geological, geomorphological, hydrological and seismic contexts of the slope. This research focuses on different mechanisms of slope instability in a glacial unloading context, especially in creeping contexts, and on damages affecting the structure of tunnels parallel to the slope. Through numerical simulations, the influence of the construction techniques was studied; so was the choice of the tunnel situation, more or less away from the slope surface. Mainly the delay time before tunnel structure implementation) on the damage lining processes, the interaction between tunnel and slope surface displacements and their time evolution have been taken into account for the most critical tunnel situation in the slope. The different situations of tunnel in the slope permit to set in evidence the safety distance from the slope in the context of a slow glacial unloading mechanism.     

Human-induced landslide on a high cut slope: a case of repeated failures due to multi-excavation

The paper attempts to represent a case of repeated failures on a high cut slope due to multi-excavation. The characteristics of each failure induced by excavation are analyzed through geological investigation, and then a geological model at different failure stages is proposed. The geological analysis shows that the excavation-induced repeated failures are related to the exposure of the weak bedding plane and the toe unloading of the cut slope. Numerical modeling is conducted based on a sequential method, taking into account the main failure stages of cut slope. The simulation results fairly coincide with the practical phenomena observed in field. It is shown that the decrease in normal stress of displaced mass on cut slope will induce the increase in shear stress in bedding planes and that at the toe of the cut slope. The released stress leads to repeated gravitational instabilities of cut slope due to the decrease in normal stress and the increase in shear stress along the bedding planes of mudstone.     

Method of mitigating the surface erosion of a high-gradient mudstone slope in southwest Taiwan

Soft mudstone dominates the rock mass at southwest Taiwan. Mudstone slakes significantly when it meets water due to a short diagenetic period and poor cementation. Gulleys are visible on the surface of mudstone slopes after rainfall. The low slaking durability resistance of the mudstone causes not only geographical badland but also erosion problems on the highway slopes in the mudstone area. An effective countermeasure for protecting the mudstone slope must contribute to a reduction in surface erosion; facilitate drainage from the slope surface during rainfall; and incorporate a high-strength structure to fight against swelling stress, preserve vegetation, and contribute to slope stabilization. In this study, a new slope erosion countermeasure, the soil-tyre-vegetation method (STV), was applied to an excavated mudstone slope in southwest Taiwan. STV utilizes waste tyres, H-beams, and geotextile. Waste tyres are good for preserving the soil for vegetation on mudstone slopes, mitigating slope erosion. The H-beams support the weight of the vegetation and the soil-filled tyres. The geotextile prevents the loss of fine-grain soil and guarantees drainage from the slope during heavy rainfall. The experimental results for a mudstone slope with a slope angle of 45° showed that STV protected the mudstone slope and improved the condition of the vegetation on it.     

某隧道边坡稳定性研究

通过对隧道边坡破坏模式分析,建立了边坡地质概化模型,确定了岩体及控制性结构面物理力学参数,并基于刚体极限平衡法对边坡在不同工况条件下的安全系数进行了计算分析,分析结果表明,目前条件下边坡整体趋于稳定,但隧道的开挖会导致边坡稳定性一定程度降低,暴雨工况会导致边坡稳定性显著降低,最后为进一步探讨边坡加固方案提出了建议。     

某矿山边坡工程地质特征与防治对策

结合广西田阳一处矿山边坡工程实例,在详细分析边坡工程地质条件的基础上,研究了该类边坡的坡体结构特征,针对稳定性评价结果和边坡的地质特征,提出了相应的防治对策,以期为西南地区类似工程提供指导。     

越南胡志明路某边坡加固设计研究

本文介绍了越南胡志明路某边坡加固设计研究结果。文中指出用于边坡设计计算的力学指标最好采用地质勘察结果与现场调查反演结果综合而得的数据。通过胡志明路边坡设计研究笔者体会到介于土质与岩质边坡之间状态的边坡采用平面滑动模型分析与圆弧滑动模型分析结果基本相同。由此笔者得出以下认识：从某种意义上讲，边坡工程设计的任务不是去进行精确的计算，而是进行正确的判断。文中通过工程实例论证得出：边坡工程稳定性分析除了地质条件是影响边坡稳定主要内因外，水的作用是影响边坡稳定的主要外因。因此水的治理和控制是边坡加固工程必须要解决的问题。     

Analysis of a rock slide stabilized with a toe-berm: a case study in British Columbia, Canada

Practical experience has shown that slope movement can be controlled by the placement of a berm near the toe of the moving mass. During construction of the Revelstoke project (British Columbia, Canada), excavation of a large highway rock cut triggered movement of a 250,000 m³ rock slide. A 15,000 m³ toe-berm was used as a temporary measure to control the displacements of the slide and allow permanent remedial measures to be completed. The rock slide was extensively investigated and monitored. The Sarma limit equilibrium method and the three-dimensional distinct element program, 3DEC were used to investigate the stabilizing effect of the toe-berm on the slope deformations. In addition, 3DEC was used to investigate the effect of internal discontinuities on slope displacements. The numerical model responded in a manner that is in general agreement with field observations and supported the observations that a small toe-berm can be an effective remedial measure in controlling slope displacements.     

矿山边坡破坏模式与稳定性评价

矿山边坡的稳定性研究一直是岩土工程领域广泛关注的热点问题之一。结合广西田阳一处矿山工程边坡的实例,在分析其破坏模式的基础上,采用刚体极限平衡法、数值模拟方法和赤平投影方法综合评价了该边坡的稳定性,三种方法互为补充,为边坡防治提供了可靠的稳定性计算成果。提出的研究方法可为西南地区类似工程提供一定的借鉴和参考。     

某二级高边坡健康监测试验研究与分析

近年来,随着中国建设事业规模的增大,多级高边坡工程安全问题日益突出,对边坡工程进行监测预警尤为必要。依托舟曲灾后重建项目某二级高边坡项目,建立了一套综合立体的自动化监测系统。通过对边坡内力、位移的监测与分析,发现了边坡在施工和运营阶段的一些变化特征和规律:边坡支护初期,应力、位移变化的幅度较大;随着支护结构与边坡内部岩体的相互调整,二者变化趋于平稳。该边坡运营阶段的最大位移变化速度为0.25mm/d0.5mm/d,监测点最大位移累积变化量小于10 mm;格构梁的内力与变形也均处于弹性范围之内。综合各项监测结果可以得出,支护结构对该边坡起到有效的加固效果,该边坡在运营阶段处于稳定状态。该试验对今后同类边坡的加固设计与监测分析具有一定的参考价值。     

Effect of a less permeable stronger soil layer on the stability of non-homogeneous unsaturated slopes

Slope failure occurs due to an increase in the saturation level and a subsequent decrease in matric suction in unsaturated soil. This paper presents the results of a series of centrifuge experiments and numerical analyses on a 55° inclined unsaturated sandy slope with less permeable, stronger silty sand layer inclusion within it. It is observed that a less permeable, stronger silty sand layer in an otherwise homogeneous sandy soil slope hinders the infiltration of water. The water content of the slope just above the stronger layer increases significantly, compared to elsewhere. No shear band is found to initiate in a homogeneous sandy soil slope, whereas for a non-homogeneous slope, they initiate just above the less pervious, stronger layer. A discontinuity of the shear zone is also observed for the case of a non-homogeneous soil slope. The factor of safety of a non-homogeneous, unsaturated soil slope decreases because of the less permeable, stronger layer. It decreases significantly if this less permeable, stronger soil layer is located near the toe of the slope.     

Prediction of grey-catastrophe destabilization time of a granite residual soil slope under rainfall

The stability of a residual soil slope is a system of grey and white, and gradual change and sudden change. It is difficult to accurately forecast the instability time of a granite residual soil slope, because the factors affecting the instability of granite residual soil slopes are random and uncontrollable. Using the grey prediction method, the accumulation generation of data weakens the influence of random disturbance factors in the original sequence, and enhances the regularity of data. In this paper, we proposed a grey cusp catastrophe prediction model to calculate the instability time of granite residual soil slopes under rainfall. We took one-time cumulative transformation of the remote monitoring data of slope displacement, and then conducted polynomial regression fitting on the processed displacement data and monitoring time. The grey cusp catastrophe instability prediction model of granite residual soil slopes was established using the nonlinear dynamic catastrophic prediction theory. The critical instability time of the slope was predicted using the grey catastrophe instability prediction method presented in this paper. For comparison, we conducted exponential curve fitting on the displacement data and monitoring time, and then established the Saito instability forecasting method of a soil slope to predict the slope instability. Through the engineering application, and using the presented grey catastrophe slope instability prediction method, the slope instability process may be accurately predicted. The calculation results using the grey catastrophe slope instability prediction method presented in this paper are in good agreement with the actual situation. Whether it can be used for other slopes remains to be further studied.

     

岩质边坡危岩最优锚固方案的确定

运用赤平板射投影，块体理论和岩本力学的基本原理，试探求证 种可供边坡工程采用的确定岩质边坡危岩最优锚固方案的简易方法。最后，试用该法对已竣工重庆大学高陡边坡危岩锚固工程进行验证分析。     

邻近建筑物某岩质高边坡的稳定性分析与评价

介绍东莞市虎门镇某岩质高边坡的支护设计方案,该边坡坡体裂隙发育且邻近建筑物,采用有限元强度折减法并运用MIDASGTS软件建立二维模型进行计算分析,结果表明其稳定性满足要求,同时根据计算结果给出结论及建议,供同行参考。     

某隧道仰坡力学参数确定及稳定性分析

对某隧道进口仰坡进行分析,在RMR评价的基础上确定岩体的力学参数,利用赤平投影法对仰坡的稳定性进行定性分析,找出其最可能的破坏形式,然后对仰坡的稳定安全系数进行了计算,结果表明,该隧道仰坡安全储备不大,隧道施工扰动下,仰坡有失稳的可能。     

预应力地梁锚索改善边坡受力状态的理论分析

边坡开挖后,原有应力平衡遭破坏,若边坡过高、过陡,将产生失稳。当采用预应力地梁锚索对坡面施加一个外力时,由于改善边坡受力状态,可继续维持稳定。但是应力状态的改善程度,每级边坡的合理高度,对此目前尚无较好的方法,本文拟对此进行初步探讨。     

考虑运行风险的某岩质边坡坡比优选分析

为了研究某水电站岩质边坡在运行期内不同坡比下的抗风险能力并优化坡比,设计了不同工况(暴雨、地震)和不同坡比下的数值模拟分析。结果表明:(1)坡比一定时,随着降雨强度增加,位移逐渐增大,拉应力则变化较小;随着地震烈度增加,位移和拉应力均逐渐增大,且趋势愈明显。(2)断层区域对坡体位移场有着明显的分割作用,顺向断层则会使应力沿断层方向发生突变。(3)暴雨和地震分别作用下,边坡越陡最大位移均出现了不同程度的减小,且地震强度越大,最大位移对坡比越敏感。(4)在考虑边坡稳定性与工程造价的前提下,对开挖坡比进行组合优化设计后在各工况下为最优选择。研究成果对该工程边坡开挖施工具有较大的参考价值。     

Prevention of Critical Building Deformations on a Slide-Prone Slope

Causes of deformations of a five-story tenement building constructed on a slope are analyzed. Engineering measures that have made it possible to terminate development of settlements of risk to the building, and prevent continued sliding of the slope are described. Results are presented for geodetic observations on the building's settlements in different years.     

大连市某边坡的稳定性及防护治理探讨

对边坡及边坡的稳定性进行了介绍,以大连市西岗区某边坡为研究实例,分析了影响该边坡稳定性的因素,指出气象气候因素是影响本地区边坡失稳的主要诱发因素,并提出边坡防治的几种常用方法,对于指导边坡治理的实践具有一定的理论和应用意义。     

深圳某边坡挡土墙及坡上建筑物桩基础的加固处理

结合某边坡挡土墙的破坏情况及该边坡上建筑物桩基础的沉降情况,通过计算及方案比较,认为采用预应力锚索加固悬臂式挡土墙以及锚杆静压桩加固边坡上建筑物桩基础的方法,能有效处理挡土墙破坏及桩基础不均匀沉降问题.     

Stability assessment of a slope under a transformer substation using numerical modelling

This paper presents an analysis of the deformation mechanism and stability assessment of a slope in Yunnan Province, China. Field investigations indicated that the deformation of the slope was caused by the combined effects of the unfavorable topographical, geological and hydrogeological conditions and the placement of man-made fill. The stability of the slope was assessed by 3D numerical modeling which showed that the factor of safety of the slope was 1.1 in the natural state but reduced to 1.03 after fill was placed. Pile reinforcement was undertaken, which raised the factor of safety to 1.27.