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1.
In Daye Iron Mine, the open-pit mining has ended and the underground mining started in 2003. The present pit slopes are as high as 430 m and the slope angle is up to 43°. During the process of open-pit to underground mining, the high-steep pit slopes would be affected by both open-pit mining and underground mining, and its deformation characteristics would become more complex. So in this paper, the trinity method of numerical simulation, model experiment and field test was adopted to analyze the displacement and stress fields systematically. The results show that: (1) Prominent rebound deformation occurs near the slope foot, which is induced by the unloading in open-pit mining. When it is backfilled to 0 m level, the rebound deformation decreases, which indicate that backfilling mass can restrict the deformation and improve the slope stability; (2) Subsidence dominates the slope deformation in open-pit to underground mining and it increases with an increasing elevation of monitoring point; the maximum horizontal displacement occurs in the lower part of the slopes, because the backfilled part is squeezed by both the north slope and the south slope, and it has a lower elastic modulus than the previous orebody; (3) The stress and its variability near the slope foot are much larger than other places, indicating that the slope foot is most affected by stress redistribution and stress concentration may occur here; the stress at other stress monitoring points changes little, indicating that the influence of open-pit to underground mining is local; (4) The effect of underground mining on the deformation of the faults is not prominent; (5) Mining operations in near-ground part affect more on the variation of deformation and stress of pit slopes than that in deeper part.  相似文献   

2.
Numerous field monitoring programs have been conducted to investigate the performance of an unsaturated soil slope subjected to rainfalls in wet seasons. Most case histories focus on the response of matric suction, which is one of the two stress-state variables governing unsaturated soil behaviour. However, effects due to another variable, net normal stress, are often ignored. Also, slope performance under alternative wet and dry seasons is rarely reported and analysed. In this study, a saprolitic hillslope situated in Hong Kong was instrumented heavily to investigate its seasonal movement due to changes of the two variables and also groundwater flow mechanism. Two-year seasonal variations of matric suction and net normal stress were monitored by tensiometers together with heat dissipation matric water potential sensors and earth pressure cells, respectively. During heavy rainstorms in wet season, there was a substantial recharge of the main groundwater table, causing a significant increase of positive pore-water pressure in deeper depths. Rupture surface likely developed at depths between 5.5 and 6 m, hence resulting in a “deep-seated” mode of downslope movement. The downslope movement resulted in a peak increase of horizontal stress. In dry seasons, matric suction of up to 190 kPa was recorded, and the associated soil shrinkage led to substantial upslope rebounds. The stress built up in wet seasons hence reduced. After monitoring period of 2 years, downslope ratcheting is identified. Up to 40 % of the downslope displacements were recovered by the upslope rebounds.  相似文献   

3.
Rainfall is considered as one of the paramount factors for slope failures in many regions around the world, particularly in tropical and subtropical regions. To study the effect of rainfall storm and its duration on the stability of slopes with a thin soft band layer, a 2D seepage numerical analysis and experimental investigation were implemented on an unsaturated model, consisting of clayey sand soils with a thin soft layer inclined to the horizontal level by 30° at a slope angle of 50°. It was subjected to intensive rainfall 20 mm/h for 8 h. Positive pore water pressures and horizontal earth pressures were monitored during the rainstorm using sensors distributed inside the experimental model. Both the experimental and numerical simulation results showed that the stability of the slope decreased during the time of the rainfall storm. Infiltration of rainwater resulted in reduction of soil shear strength, due to the loss occurring in soil suction after 1 h of rainstorm; the tension cracks appeared at the top of the slope and a certain displacement was observed in the sliding blocks. During the time of rainstorm, the infiltrated water flowed out from the slope through the weak interlayer near to the toe causing piping and local failure, so the formed cracks at the top of slope grew and expanded due to sliding of the failed soil blocks. Moreover, the ground water table rose and the positive pore water pressures increased, resulting in a reduction of effective stress, which is considered as a main factor in soil shear strength. A surface runoff was also present following the full saturation of the slope, leading to dragging the fine particles with water flow causing erosion. The combination of piping and erosion effects led to a quick local failure at the toe, as well as sliding of the failed blocks and spreading of the cracks.  相似文献   

4.
A series of benched excavations were typically carried out on the bedrock slope surface to improve the stability of the soil–rock mixture (S–RM) fill slope. It is difficult to devise an in situ, large-scale direct shear test for the interphase between the S–RM fill and the benched bedrock slope surface. This study introduced a comprehensive approach to investigate the shear deformation and strength of the interphase. First the soil–rock distribution characteristics were analyzed by test pitting, image analysis, and sieve test. Then the PFC2D random structure models with different rock block size distributions were built, and large-scale numerical shear tests for the interphase were performed after calibrating model parameters through laboratory tests. The stress evolution, damage evolution and failure, deformation localization (based on a principle proposed in this paper), rotation of rock blocks, and shear strength were systematically investigated. It was found that as the rock block proportion and rock block size (rock block proportion of 50 %) increase, the fluctuations of the post-peak shear stress–displacement curves of the interphase become more obvious, and the shear band/localized failure path network becomes wider. Generally, smaller rock blocks are of greater rotation angles in the shear band. The peak shear stress and internal friction angle of the interphase increase, while the cohesion decreases with growth of the rock block proportion. However, all these three parameters increase as the rock block size (rock block proportion of 50 %) increases.  相似文献   

5.
刘力 《岩土工程技术》2014,28(5):217-220
高填方粘性土边坡的稳定性以往研究较多,为了研究变形特性与强度都不同于粘性土的高填方粗粒土边坡,运用ABAQUS软件,采用强度折减法对多级加筋粗粒土边坡工程做了有限元数值模拟,分析了整个边坡的稳定性.研究结果表明,加筋不仅提高了各个台阶的局部稳定性,也加强了边坡的整体稳定;边坡中都存在水平位移,最大值出现在边坡底部坡脚附近,在坡脚处出现小部分沿x轴正向的负位移;水平位移随着填土高度的增加而减小,第一台阶的水平位移最大;越靠近边坡,土工格栅和土体的位移均越大,变大的趋势近似一致,但土体的水平位移明显大于土工格栅的水平位移.  相似文献   

6.
Laxiwa Hydropower Station is the largest among those hydropower stations in the upper reaches of the Yellow River. The construction started in October 2001, diversion tunnel was finished in January 2004, and impoundment started in March 2009. However, from May 2009, the right-bank slope of the reservoir about 700 m high and 1,000 m wide located 500 m far from the dam was found to be deforming greatly and continuously. Although this slope had been identified as an old landslide, the survey before the construction of the dam concluded that this slope being composed of granite is stable and would be stable even after the impoundment, and thus no detailed monitoring of the slope deformation had been performed before the visible deformation occurred after the impoundment. To indentify the relationship between the deformation of the slope and impoundment, we utilized differential synthetic aperture radar interferometry and Advanced Land Observing Satellite Prism data to analyze the slope deformation before and after impoundment. We found that no identifiable deformation took place before the impoundment, while during the period of 3 April 2009 to 22 May 2010, after impoundment, maximum horizontal displacement reached approximately 7.5 m. This slope is still deforming even after a total horizontal displacement of several tens of meters being reached, showing high risk of catastrophic failure.  相似文献   

7.
A full-scale landslide-triggering experiment was conducted on a natural sandy slope subjected to an artificial rainfall event, which resulted in mobilisation of 130 m3 of soil mass. Novel slope deformation sensors (SDSs) were applied to monitor the subsurface pre-failure movements and the precursors of the artificially triggered landslide. These fully automated sensors are more flexible than the conventional inclinometers by several orders of magnitude and therefore are able to detect fine movements (<?1 mm) of the soil mass reliably. Data from high-frequency measurements of the external bending work, indicating the transmitted energy from the surrounding soil to these sensors, pore water pressure at various depths, horizontal soil pressure and advanced surface monitoring techniques, contributed to an integrated analysis of the processes that led to triggering of the landslide. Precursors of movements were detected before the failure using the horizontal earth pressure measurements, as well as surface and subsurface movement records. The measurements showed accelerating increases of the horizontal earth pressure in the compression zone of the unstable area and external bending work applied to the slope deformation sensors. These data are compared to the pore water pressure and volumetric water content changes leading to failure.  相似文献   

8.
严琼  吴顺川  周喻  张铎  宋伟超 《岩土力学》2015,36(Z2):47-56
以河北省某露天铁矿边坡为工程背景,采用连续-离散耦合数值分析方法,对典型边坡断面进行分步开挖,结合强度折减法,计算分析坡体的变形规律和受力特征。连续、离散网格区域分别采用有限差分FLAC和颗粒离散元PFC进行建模,着重从连续-离散模型的数据一致性,剪应变增量的形成、发展与局部位移的关系,连续-离散介质受力与位移过程,离散体细观破裂与坡体塑性变形等方面,对边坡稳定性的耦合分析方法进行研究,从宏观和细观角度对边坡的失稳机制进行了较为全面的探索。结果表明:(1)计算过程中坡体应力和位移在连续域和离散域保持了较高的一致性,连续-离散耦合分析方法适用于边坡稳定性研究;(2)作为边坡失稳判据的剪应变增量变化过程主要受岩土体水平位移控制;(3)细观破裂机制可有效表征边坡的宏观塑性变形;(4)土体颗粒接触力链的方向改变是土体位移和变形的驱动因素。  相似文献   

9.
江学良  杨慧  曹平 《岩土力学》2011,32(4):1234-1240
采用SURPAC建立了瓮福磷矿穿岩洞矿段采场的三维地质模型,利用接口程序将模型导入FLAC3D对采空区与露采边坡之间的相互影响进行了计算,并在边坡坡顶、坡脚与采空区四周布置了监测点以监测各点应力与位移的变化。计算结果表明:采空区的存在极大地改变了采空区周边与边坡的应力分布;使得采空区周边水平位移出现明显增加,并且改变了采空区位置周边的竖向位移场,对各个采空区之间的区域的影响最为显著,使得回弹量减小;边坡与采空区监测点的应力与位移随着边坡露采的进行出现规律性的变化;采空区的存在极大地改变了岩体塑性区的分布,对于有采空区边坡,塑性区分布范围随着开挖的进行有减小的趋势,但坡面上出现明显的拉伸破坏区,不利于边坡稳定;采空区使得露采边坡的安全系数降低。  相似文献   

10.
In the effective stress equation for unsaturated soils proposed by Bishop, shear strength in these soils depends on the effective stress parameter, χ, a function of soil suction [1]. To estimate the shear strength of unsaturated soils, one must already know this parameter and its variation with soil suction. Though theories on the shear strength of unsaturated soils are consistent with experimental measurements, estimating the effective stress parameter directly from tedious laboratory tests is impractical. Thus, researchers have performed numerous intensive studies to effectively obtain the unsaturated shear strength using simplified empirical methods.This paper shows an adaptive learning neural network method for predicting this parameter, χ. The proposed network is a multilayer perceptron network with six neurons in the input layer representing the air entry value, the volumetric water content at residual and saturated conditions, the slope of soil water characteristic curve, the net confining stress and suction. The available literature uses a database prepared from triaxial shear test results to train and test the network. The results show the suitability of the proposed approach for estimating the effective stress parameter. Network analysis indicates that the χ-parameter depends strongly on the net mean stress.  相似文献   

11.
刘杰  李建林  屈建军  陈星  李剑武  骆世威 《岩土力学》2010,31(11):3619-3626
在现阶段工程运用中,卸荷岩体力学理论中还需完善和扩充的几个方面为①锚索施加前后卸荷效应对边坡水平位移的影响;②超前开挖锚固滞后的方案会对具体工程岩体水平位移产生的影响;③关键工程结构面连通率对卸荷岩体位移的影响;④地震作用下卸荷岩体的水平位移响应;⑤地震作用下不同连通率对水平向位移的影响。针对此,以大岗山坝肩边坡为对象展开研究。分析指出岩体开挖卸荷后回弹变形和压缩变形都会大于未考虑岩质劣化时的计算变形。同时指出,卸荷条件下两种施工方案对坡面的水平向位移造成的影响较小,为超挖多级而锚固措施相对滞后的现场施工过程的可行性提供依据。统计出各剖面在不同高程水平位移随地震加速度发展特征,建议水平位移随地震加速度呈非线性变化区域为防震抗震重点加固区域。研究发现,连通率的增大会导致卸荷裂隙XL9-15,XL316-1的塑性区发育明显增大,而裂隙范围内塑性区的加剧不会明显地反映在坡面关键点的变化上,开挖工况可能造成表观位移较小的突发性崩塌。  相似文献   

12.
In order to study the dynamic response characteristics of a rock slope with discontinuities under the combined action of earthquakes and rapid water drawdown, a large-scale shaking table test was performed on a rock slope with discontinuous joints. Wenchuan earthquake (WE) seismic records were performed to investigate the horizontal and vertical acceleration response and displacement response. In particular, three-dimensional optical measurement techniques was used to obtain the slope surface displacements. A comparison was made on the seismic response according to the analysis of PGD (peak ground displacement) and M PGA (acceleration amplification coefficient) of the modeled slope. The results show that the experimental slope mainly underwent settlement and horizontal deformation when the WE records were applied in the z and x directions, respectively. The slope was first shaken by the P wave, which caused the differential settlement to occur at the surface slope; then, the slope was shaken more severely by the S wave, which led to a greater horizontal deformation. Moreover, analysis of the ΔPGD (increment of PGD) and ΔM PGA (increment of M PGA) under rapid drawdown suggests that the rapid water drawdown mainly impacts the deformation of the surface slope, particularly between the high and low water levels. The water infiltration through the cracks softened the material of the surface slope, and the rapid drawdown also enhanced the slope deformation. In addition, the damage evolution process of the slope can be identified, mainly including three stages: an elastic stage (<?0.168 g), a plastic stage (0.168–0.336 g), and a failure stage (>?0.336 g).  相似文献   

13.
Landslides are frequently occurring natural hazards in Nilgiris district of Tamil Nadu, India, particularly during monsoon season. The present study describes the geotechnical characterization and analysis of rainfall-induced landslide that occurred at Marappalam location of Nilgiris district on November 10, 2009. The detailed investigation comprises mapping of landslide, topographical survey, field and laboratory investigations, characterization of soil and rock, and numerical analysis. Field study comprises borehole and geophysical investigations. Detailed laboratory investigation was performed to identify index and engineering properties of soil and rock. Based on the results obtained from field and laboratory investigations, the generalized subsoil profile of Marappalam slope has been plotted. The investigations revealed that loose and soft soil layer with low permeability and plasticity interspersed with boulders could be the main source of debris flow. Scanning electron microscopic analysis and x-ray diffraction analysis were performed to study the influence of weathering on slope failure. Failure mechanism of Marappalam 2009 landslide was identified from the numerical analysis performed using landslide simulation program LS-RAPID. The analysis revealed that the 5-day antecedent rainfall (303 mm) and intense rainfall on 10th November 2009 (405 mm) saturate the slope due to infiltration of rainwater. This leads to a decrease in the matric suction and subsequent development of positive pore water pressure, which in turn reduces the shear resistance of the soil along with shear displacement, and resulted in a progressive failure.  相似文献   

14.
复杂应力状态下土质高边坡稳定性分析   总被引:1,自引:1,他引:0  
马宗源  廖红建  祈影 《岩土力学》2010,31(Z2):328-334
结合现有的实际滑坡场地,开展了关中盆地黄土塬边的高边坡稳定性研究。基于弹塑性理论和非关联流动法则,根据双剪统一强度理论,建立了双剪统一弹塑性本构模型的显式有限差分格式。针对陕西省泾阳县南塬高边坡滑坡的现场勘测和室内试验,分析了滑坡的规模和滑坡前后的地形特征。在此基础上,还原了滑坡前的边坡地形概状,建立三维计算模型并运用三维拉格朗日有限差分方法分析了中间主应力对高边坡稳定性的影响;然后考虑中间主应力的影响对不同地下水埋深和渗流时边坡的稳定性进行分析。结果表明,考虑中间主应力情况下,随着地下水位升高,坡顶水平向位移增大;当不考虑渗流时,坡顶水平位移增大到一定值后边坡达到稳定状态,而考虑渗流时坡顶水平位移持续增大,并且容易发生突然的破坏失稳。期望对泾阳南塬滑坡群的破坏机制研究提供一定参考。  相似文献   

15.
以功东高速大营盘碎石土深路堑高边坡为研究对象,对其用有限差分软件FLAC3D模拟分析,在低频高幅的地震波作用下,深入考虑网格划分和输入波以保证模拟的准确性,以此来研究高烈度地区地震作用下高边坡开挖及时支护的工序下的自然和降雨工况不同的变形和动力响应规律。结果表明:(1)在静力开挖支护阶段,开挖主要影响范围为开挖面附近的土体,位移主要为回弹变形,随着开挖深度的增加,回弹位移增加变缓。向下坡方向的位移趋势从坡脚开始产生,在降雨工况下所有坡面测点均产生向下坡方向位移。(2)地震作用下,坡体会产生多条剪切带倾泄能量,而地震降雨工况下产生坡顶到坡脚的贯通剪切带,成整体失稳趋势。(3)输入地震波峰值及其在此峰值点的位移响应存在时间差,且此点位移也不是位移最大值,降雨对中上部坡体位移影响较大,会使位移较自然工况下几乎成倍增加。(4)在地震中下坡方向的水平位移越大,其加速度响应越有降低的趋势,且越往坡体内部,降雨对加速度响应影响越不明显。  相似文献   

16.
延安市阳崖黄土边坡开挖破坏离心模拟试验研究   总被引:1,自引:0,他引:1  
人工开挖是黄土地区滑坡形成的主要诱发因素之一,开挖导致斜坡一定范围内产生卸荷回弹和应力重分布,斜坡应力重新平衡的过程伴随着斜坡形变,甚至破坏。延安市宝塔区枣园镇阳崖滑坡为典型开挖诱发的黄土边坡,本文选取阳崖滑坡为地质原型,采用TLJ-500大型土工离心机对边坡坡脚开挖状态下变形破坏过程进行模拟试验,通过对模型控制点监测数据分析,研究边坡坡脚开挖前后坡体形变位移特征、坡体内部土压力响应特征以及边坡变形破坏机理。结果表明:坡脚开挖后临空面附近产生局部垮塌,其坡体位移、潜在滑移面以及拉张裂缝均由坡体前缘往后部渐进性变化发展。开挖后坡体内部产生明显的应力松弛,且越靠近开挖面卸荷效应越明显,开挖主要影响坡体的中前部分,对坡体后部影响较小甚至无影响,分析得知坡体变形破坏机理为典型的渐进后退式。  相似文献   

17.
Transient seepage in unsaturated soil slope is one of the significant triggering factors in rainfall-induced landslides. Rainfall infiltration leads to the decrease in stabilizing effect because of increased positive pore-water pressures. SEEP/W and SLOPE/W used in this study have been widely employed to describe frameworks for understanding transient seepage in soil slope, and to perform slope stability analyses, respectively. The study area is in Sichon District in Nakhon Si Thammarat Province, southern Thailand. A landslide there was investigated by modeling the process of rainfall infiltration under positive and negative pore-water pressures and their effects on slope stability. GIS (Geographic Information System) and geotechnical laboratory results were used as input parameters. The van Genuchten’s soil water characteristic curve and unsaturated permeability function were used to estimate surface infiltration rates. An average rainfall was derived from 30-year monthly rainfall data between 1981 and 2011 in this area reported by the Thailand Royal Irrigation Department. For transient condition, finite element analysis in SEEP/W was employed to model fluctuations in pore-water pressure during a rainfall, using the computed water infiltration rates as surface boundary conditions. SLOPE/W employing Bishop simplified method was then carried out to compute their factors of safety, and antecedent precipitation indices (API) calculated. Heterogeneous slope at the site became unstable at an average critical API (APIcr) of 380 mm, agreeing well with the actual value of 388 mm.  相似文献   

18.
The Kualiangzi landslide was triggered by heavy rainfalls in the “red beds” area of Sichuan Basin in southwestern China. Differing from other bedrock landslides, the movement of the Kualiangzi landslide was controlled by the subvertical cracks and a subhorizontal bedding plane (dip angle < 10°). The ingress of rainwater in the cracks formed a unique groundwater environment in the slope. Field measurement for rainfall, groundwater movement, and slope displacement has been made for the Kualiangzi landslide since 2013. The field monitoring system consists of two rainfall gauges, seven piezometers, five water-level gauges, and two GPS data loggers. The equipments are embedded near a longitudinal section of the landslide, where severe deformation has been observed in the past 3 years. The groundwater responses to four heavy rainfall events were analyzed between June 16 and July 24 in 2013 coincided with the flood season in Sichuan. Results showed that both of the water level and the pore-water pressure increased after each rainfall event with delay in the response time with respect to the precipitation. The maximum time lag reached 35 h occurred in a heavy rainfall event with cumulative precipitation of 127 mm; such lag effect was significantly weakened in the subsequent heavy rainfall events. In each presented rainfall event, longer infiltration period in the bedrock in the upper slope increased the response time of groundwater, compared to that of in the gravels in the lower slope. A translational landslide conceptual model was built for the Kualiangzi landslide, and the time lag was attributed to the gradual formation of the uplift pressure on the slip surface and the softening of soils at the slip surface. Another important observation is the effect on the slope movement which was caused by the water level (H w) in the transverse tension trough developed at the rear edge of the landslide. Significant negative correlation was found for H w and the slope stability factor (F s), in particular for the last two heavy rainfall events, of which the drastic increase of water level caused significant deterioration in the slope stability. The rapid drop (Δ?=?22.5 kPa) of pore-water pressure in the deep bedrock within 1 h and the large increase (Δ?=?87.3 mm) of surficial displacement were both monitored in the same period. In the end, a four-level early warning system is established through utilizing H w and the displacement rate D r as the warning indicators. When the large deformation occurred in flood season, the habitants at the leading edge of the landslide can be evacuated in time.  相似文献   

19.
Shallow landslides (i.e. 1–2-m depth) on both man-made and natural slopes are of major concern worldwide that has led to huge amount of socio-economical losses. The use of vegetation has been considered as an environmentally friendly means of stabilising slopes. Existing studies have focused on the use of plant roots with different geometries to mechanically stabilise soil slopes, but there are little data available on the contribution of transpiration-induced suction to slope stability. This study was designed to quantify both the hydrological and mechanical effects of root geometry on the stability of shallow slopes. Centrifuge tests were conducted to measure soil suction in slope models supported by newly developed artificial roots. These artificial roots exhibit three different representative geometries (i.e. tap, heart and plate) and could simulate the effects of transpiration. The measured suction was then back-analysed through a series of finite element seepage-stability analyses to determine the factor of safety (FOS). It is revealed that after a rainfall event with a return period of 1000 years, the slope supported by heart-shaped roots retained the highest suction within the root depth, and thus, this type of root provided the greatest stabilisation effects. The FOS of the slope supported by the heart-shaped roots, through both mechanical reinforcement and transpiration-induced suction, is 16 and 28 % higher than that supported by the tap- and plate-shaped roots, respectively.  相似文献   

20.
为了研究复杂应力条件下原状黄土的增湿变形特性,利用改进的非饱和土湿陷真三轴仪,在测量吸力条件下对原状黄土进行双线法分级浸水增湿试验,探讨力?水耦合作用下吸力的变化特性,研究真三轴浸水试验的增湿变形特性,以及吸力、净围压、中主应力和应力比对增湿变形的影响。研究结果表明:由ei-lgp压缩曲线确定了非饱和土的屈服点,屈服点之前,曲线的斜率近似相等;屈服点之后,曲线的斜率随着初始吸力的减小而减小,且非饱和土与饱和土的交点随着初始吸力的增大呈右下方移动趋势。等向压缩过程中,吸力随着净平均应力的增加近似呈线性减小趋势,初始吸力越小,吸力减小的速度越慢,且吸力变化量越小。均压分级浸水增湿时,吸力s随着浸水量w的增加而减小,增湿体变 随着浸水量w的增加而增大,不同净围压下的 -w关系曲线相互有交叉。交叉区域之前,净围压越大,增湿体变越小,而交叉区域之后,净围压越大,增湿体变越大。在同一净围压条件下,浸水量相同时,初始吸力越大,增湿体变越大。真三轴剪切增湿试验中,应力比k、中主应力参数b值和净围压?3皆对增湿变形有一定的影响。当q/p≤1时,增湿变形曲线前段下凹后段上凹,主要表现为体积增湿变形;当q/p>1时,增湿变形曲线只有下凹部分,主要表现为剪切增湿变形。增湿变形曲线的形态取决于k值和b值的不同组合。  相似文献   

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