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1.
This paper evaluates the stability of long and steep slopes examining the effect of the critical length/depth ratio, L/H, and critical slope angle, β cr, by comparing the results of infinite slope equation with the spectral element method. In addition, the influence of uphill and downhill boundaries on stability of long and steep slopes is also evaluated in theoretical domains. As an example, this paper presents a stability analysis of long and steep vegetated and barren slopes in saturated and seismic conditions, and also evaluates the effectiveness of the infinite slope equation for those slopes. In the vegetated slopes, the root zone may not extend to the whole depth of slope, which may lead to overestimating the factor of safety by infinite slope equation. This paper examines the applicability of the infinite slope equation for infinitely long, steep, and shallow slope model by comparing the results of the spectral element method. 相似文献
2.
The stability problem of natural slopes, filled slopes, and cut slopes are commonly encountered in Civil Engineering Projects. Predicting the slope stability is an everyday task for geotechnical engineers. In this paper, a study has been done to predict the factor of safety (FOS) of the slopes using multiple linear regression (MLR) and artificial neural network (ANN). A total of 200 cases with different geometric and shear strength parameters were analyzed by using the well-known slope stability methods like Fellenius method, Bishop’s method, Janbu method, and Morgenstern and Price method. The FOS values obtained by these slope stability methods were used to develop the prediction models using MLR and ANN. Further, a few case studies have been done along the Jorabat-Shillong Expressway (NH-40) in India, using the finite element method (FEM). The output values of FEM were compared with the developed prediction models to find the best prediction model and the results were discussed. 相似文献
3.
提出一种基于有限元计算的边坡三维滑裂面搜索的方法,根据有限元计算的应力结果,计算可能滑裂面的安全系数,然后用遗传算法搜索出最危险滑裂面,并得出相应的安全系数作为边坡的安全度评价指标。该方法的优越性是只需进行一次有限元计算,不需要假定滑裂面,可以用于具有复杂地貌和地质构造的三维边坡。通过算例,验证该方法的可行性和程序的正确性,以大岗山水电站库区边坡工程实例验证该方法的实用性。 相似文献
4.
Jianqiang Mao 《国际地质力学数值与分析法杂志》2005,29(5):525-550
This paper presents a finite element approach to solve geotechnical problems with interfaces. The behaviours of interfaces obey the Mohr–Coulomb law. The FEM formulae are constructed by means of the principle of virtual displacement with contact boundary. To meet displacement compatibility conditions on contact boundary, independent degrees of freedom are taken as unknowns in FEM equations, instead of conventional nodal displacements. Examples on pressure distribution beneath a rigid strip footing, lateral earth pressure on retaining walls, behaviours of axially loaded bored piles, a shield‐driven metro tunnel, and interaction of a sliding slope with the tunnels going through it are solved with this method. The results show good agreement with analytical solutions or with in situ test results. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
有限元数值计算方法在岩土工程中已有较多的应用,但在水平受荷桩分析计算中的应用尚不普遍。有关水平受荷桩土体系水平承载力及变形的数值模拟方法少有文献报道。采用有限元数值模拟方法来研究水平受荷桩土体系的水平位移。首先简要分析了水平受荷桩的主要计算方法及原理。然后,基于ABAQUS软件建立了桩土系统二维及三维的有限单元模型,分别通过按现行规范推荐的m法和按Poulos的弹性理论法计算的两个算例,将数值计算方法与解析方法进行了对比计算分析。有限元数值计算结果与解析解基本吻合,说明了所采用有限元数值模拟方法的可靠性及有效性。 相似文献
6.
Two‐dimensional slope stability analysis for a slope with a row of drilled shafts needs a mechanism to take into account the three‐dimensional effect of the soil arching due to the spaced drilled shafts on slope. To gain a better understanding of the arching mechanisms in a slope with evenly spaced drilled shafts socketed into a stable stratum (or a rock layer), the three‐dimensional finite element modelling technique was used for a comprehensive parametric study, where the nonlinear and plastic nature of the soil and the elastic behavior of the drilled shafts as well as the interface frictions were modelled. Various factors were varied in the parametric study to include (1) the rigidity of the drilled shafts as influenced by its diameter, modulus of elasticity, and total length; (2) shafts spacing and location on the slope; (3) the material properties of rock and the socket length of shaft; and (4) the soil movement and strength parameters. Evidences of soil arching and reduction in the stresses and displacements through the load transfer mechanisms due to the presence of the drilled shafts were elucidated through the finite element method (FEM) simulation results. Design charts based on regression analysis of FEM simulation results were created to obtain a numerical value of the load transfer factor for the arching mechanism provided by the drilled shafts on the slope. Observations of the arching behavior learned from the FEM simulations provide an insight into the behavior of drilled shafts stabilized slope. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
基于边界元法的边坡矢量和稳定分析 总被引：4，自引：0，他引：4
矢量和法物理力学意义明确,计算简单,且能根据边坡当前的应力分布状态合理地评价其整体稳定性状态。其中边坡的应力状态通常是采用有限元法来求解。由于边界元法具有研究问题降阶、离散化带来的误差值仅产生在边界以及计算量小等优点,在工程中得到了广泛应用;对于平面问题,以源点作为原点,以所积分单元的切向和法向为坐标轴建立局部坐标系,对于线性单元可以得到所有积分的解析解。因此,可以得到计算区域内部任意点的场变量的解析解,这就保证了位于边界附近区域场变量的精度。利用边界元法得到二维边坡体内连续的应力分布状态,使用矢量和法对该边坡进行稳定性分析,并且与基于有限元的矢量和法、极限平衡法进行对比分析。边坡圆弧滑面和折线滑面的计算结果表明,基于边界元法得到的矢量和安全系数和基于有限元的矢量和法、极限平衡法基本一致;边界元法对应的矢量和安全系数对边界单元尺寸不敏感。 相似文献
8.
Stability of partially submerged slopes is analysed when dealing with water front structures such as reservoirs. This work presents a numerical study of the stability of partially submerged cohesionless slopes under no flow conditions. The analysis shows that critical conditions occur when water level is located close to the mid‐height of the slope. Safety factor for such cases may be significantly lower than the classical result tan(?)/tan(β), and the critical slip surfaces does not approach the surface of the slope. This apparent anomaly is related to a reduction in normal stresses and frictional resistance over submerged parts of the slip surface. These effects are particularly significant for flat slopes and low ratios of submerged to total unit weights. Commercially available slope stability software using common slope stability methods (e.g. Bishop's) can detect this behaviour with reasonable accuracy; however, when conducting such an analysis, the user needs to be aware of the counterintuitive behaviour of partially submerged cohesionless slopes in order to analyse the critical conditions. An instructive stability chart provides an overview of the effects of submergence thus drawing the attention of professionals to the observed phenomenon and its potential extent. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
Finite element modeling approach to assess the stability of debris and rock slopes: a case study from the Indian Himalayas 总被引：4，自引：2，他引：2
Landslides and slope failures are recurrent phenomena in the Indian Himalayas. The study area comprises the hill slopes along a road stretch of 1.5 km at a distance of 9 km from Pipalkoti on Chamoli–Badrinath highway (NH-58) in the Garhwal Himalayas, India. Based on the field survey, contour map, and the hillshade, the study area has been divided into different zones. Three different zones/slopes in this study area including one potential debris slide, one stable debris slope, and one potential rock slide have been undertaken for investigation and modeling. Field mapping, data collection related to slope features and soil/rock sample collection, and discontinuity mapping for all the slopes have been carried out in field. Soil samples have been tested in the laboratory to determine the physico-mechanical properties. These properties along with some material properties from the literature have been used as input parameters for the numerical simulation. To investigate the failure process in the debris/rock slides as well as stable debris slope, the slopes were modeled as a continuum using 2D finite element plain strain approach. Shear strength reduction analysis was performed to determine the critical strength reduction factor. The computed deformations and the stress distributions, along the failure surface, have been compared with the field observations and found to be in good agreement. The analysis results indicated rock/debris slide slopes to be highly unstable. The debris slide modeling depicted failures both above and below road levels as observed in field. The rock slide modeling could depict the exact pattern of failure involving 3 sets of discontinuities simultaneously as observed in real-field scenario which is a major limitation in case of limit equilibrium analysis. The field-observed stable slope comes to be stable through FE analysis also. Based on these analyses, landslide hazard assessment of the study area could be done. 相似文献
10.
11.
A micromechanical model is proposed for studying the stability and failure process of slopes based on the gravity increase method (GIM). In this numerical model the heterogeneity of rock at a mesoscopic level is considered by assuming that the material properties conform to the Weibull distribution. Elastic damage mechanics is a method used for describing the constitutive law of the meso-level element, the finite element method (FEM) is employed as the basic stress analysis tool, and the maximum tensile strain criterion and the Mohr–Coulomb criterion are utilised as the damage threshold. The numerical model is implemented into the Realistic Failure Process Analysis (RFPA) code using finite element programming, and an extended version of RFPA, i.e., RFPA-GIM, is developed to analyse the failure process and stability of slopes. In the numerical modelling with RFPA-GIM, the critical failure surface of slopes is obtained by increasing the gravity gradually but keeping material properties constant. The acoustic emission (AE) event rate is employed as the criterion for slope failure. The salient feature of the RFPA-GIM in stability analysis of slopes is that the critical failure surface as well as the safety factor can be obtained without any presumption for the shape and location of the failure surface. Several numerical tests have been conducted to demonstrate the feasibility of RFPA-GIM. Numerical results agree well with experimental results and those predicted using the FEM strength reduction method and conventional limit equilibrium analysis. Furthermore it is shown that selection of the AE rate as the criterion for slope failure is reasonable and effective. Finally, the RFPA-GIM is applied to several more complex cases, including slopes in jointed rock masses and layered rock formations. The results indicate that the RFPA-GIM is capable of capturing the mechanism of slope failure and has the potential for application in a larger range of geo-engineering. 相似文献
12.
Volume estimate of flow-type landslides along carbonatic and volcanic slopes in Campania (Southern Italy) 总被引：1，自引：0，他引：1
Recent studies on flow-type landslides in pyroclastic deposits have been performed to identify potential source areas and
the main depositional mechanisms. Interesting methods for mapping landslide susceptibility have also been proposed. Since
the potential volume of flow-type landslides is a measure of event magnitude, hence of considerable use in hazard assessment,
we propose a method to estimate the potential volume for the morphometric analysis of 213 flow-like landslides occurred in
Campania in recent centuries. First, our data show that the height, H, of the detachment and erosion-transport zones (i.e. the difference in height between the top of source area and a point,
the first break at the foot of the slope, where the deposition stars to take place and the landslide loses velocity) and the
area, A
f, of the same zones are linked by a mathematical function. Secondly, only part of the entire thickness of the pyroclastic
material on the slope is involved. To define the potential volumes of the flow-type landslides, we analysed slopes, both in
volcanic and carbonatic contexts, considering both channelled and unchannelled flow-type landslides. The most susceptible
areas are identified by using a landslide-triggering susceptibility map, and then in each case the height H was estimated. This height is the difference in level between the point on the slope with highest susceptibility and the
first break at the foot of the slope. Using the statistical correlation between H and A
f, both calculated for historical landslides, we evaluate the area of a potential landslide on a slope. Finally, potential
volumes are calculated by using A
f and a constant thickness of the pyroclastic cover for the whole slope. This method could represent a useful tool to detect
the main areas where risk mitigation works are required. 相似文献
13.
Embankment slopes composed of spatially variable soils have a variety of different failure modes that are affected by the correlation distances of the material properties and the geometry and total length of the slope. This paper examines the reliability of soil slopes for embankments of different length and uses parallel computing to analyse very long embankments (up to 100 times the embankment height) for a clay soil characterised by a spatially varying undrained shear strength. Based on a series of analyses using the 3D random finite element method (RFEM), it is first shown that the reliability of slopes of various length can be efficiently computed by combining simple probability theory with a detailed 3D RFEM analysis of a representative shorter slope of length 10 times the slope height. RFEM predictions of reliability indices for longer slopes are then compared with results obtained using Vanmarcke's (1977a) simplified 3D method and Calle's (1985) extended 2D approach. It is shown that these methods can give significantly different results, depending on the horizontal scale of fluctuation relative to the slope length, with RFEM predicting a lower slope reliability than the Vanmarcke and Calle solutions in all cases. The differences in the solutions are evaluated and attributed to differences in the assumed and computed failure surface geometries. 相似文献
14.
针对目前岩土工程中锚杆数值模型存在的局限性,受商用软件中锚杆强度模型的启发而提出了一种适用于强度折减有限元法的锚杆强度模型,并建议了考虑锚杆强度折减的强度折减方法,研制了相应程序。该模型应用于岩坡锚固计算,计算结果说明了模型的有效性;应用于土质边坡稳定性评估计算,结果表明模型方便可行。 相似文献
15.
对于分级修建的边坡,如何选择合适的平台宽度还有待研究。利用离心模型试验和有限元强度折减法对加筋土边坡进行分析,探讨平台分级的影响。试验表明,设置平台可以使边坡分解成若干个次级边坡,边坡分级后,其整体破坏向各个次级边坡集中,失稳部分的规模有所减少;加筋增强了边坡的整体性,能够强化次级边坡之间的独立性;合适的宽度可以使滑动面只发生在次级边坡中,对整体安全是有利的。有限元计算表明,边坡高度较大时,土的黏聚力的作用就会削弱,通过将高大的边坡变成高度较小的次级边坡,能够充分发挥黏聚力对边坡稳定的作用。而加筋的主要效果就是给土体提供一个似黏聚力。也就是说,合适的边坡高度分级能够充分发挥筋材的加筋效果。另外,对加筋高边坡来说,筋材的模量和延伸率是更为关键的材料参数。延伸率不足,在其他筋材的强度还没有发挥时被拉断,就达不到共同承载的目的。 相似文献
16.
Ground movement analysis of soil nailing construction by three-dimensional (3-D) finite element modeling (FEM) 总被引：10，自引：0，他引：10
In recent years, soil nailing has been widely used to stabilize excavated steep slopes. Its design is often controlled by the allowable deformation level especially when buildings and/or other underground facilities exit near the excavation. In this paper a three-dimensional (3-D) finite element model (FEM) has been developed for the deformation analysis of nailed soil structures. In this model, the soil nonlinearity, the soil–nail interaction and the staged construction are all considered. Parametric studies are carried out to investigate some influence factors on the deformation behavior. An engineering case is also analyzed and the predicted soil movements at various stages of excavation are compared with field measurements. Good agreement between the prediction and the measurements proves the reliability of the model. 相似文献
17.
Partially submerged c′ − φ′ slopes with a horizontal water table exhibit a critical pool level at which the factor of safety becomes a minimum. The phenomenon was first identified using finite element methods, but in this paper, a more thorough analytical investigation is presented. The approach described herein assumes a rigid block sliding with a circular failure mechanism, combined with optimization software to identify the critical circle. The method is initially validated against known slope solutions that assume circular and log-spiral mechanisms and shown to give excellent agreement, especially for flatter slopes. The method is then applied to partially submerged slopes with a focus on the critical pool level. Through detailed investigation of the overturning and restoring moments in the stability analyses, the critical pool level phenomenon is shown to lie in the trade-off between the destabilizing effects of internal pore pressures on soil strength and the stabilizing effect of external hydrostatic water pressures on the slope surface. 相似文献
18.
Himalayan mountain chains are neo-tectonically active and significantly susceptible to frequent geohazards like landslides, earthquakes, cloudburst and flash floods, etc. Himalayan slopes are characterized by highly fractured, jointed and sheared rock mass. This affects the strength of the rocks and thus largely influences the stability characteristic of slopes which have been aggravated by human intervention. The ongoing developmental activities, particularly in the last two decades, are responsible for large-scale destabilization of slopes. In rugged terrain, safer designs along hill-cut roads must be ensured. Despite extensive geotechnical works for slope stabilization done in the Himalayan range, slope sections evolve due to various natural and man-made factors are need to be understood in greater details. Proper evaluation and treatment were done on the cut slopes that are severely affected during Kedarnath disaster of June 2013. One of such roads is national highway from Rudraprayag to Gaurikund near Kedarnath. In this study, the stability of vulnerable road cut slopes from Rudraprayag to Agastmuni was investigated. Three key road cut slopes were considered. Finite element analysis was conducted using PLAXIS simulator. Factors of safety, stress, strain, horizontal and vertical displacement have been determined for each slope. The most unstable slope had a factor of safety (FoS) equal to 0.935, while the most stable slope had FoS equal to 2.56. Outcomes from simulation are in good agreement with the prevailing field conditions. Slope stability evaluation must be performed to ensure better safety and to achieve disaster mitigated design. 相似文献
19.
Finite Element (FE) pseudo-static analysis can provide a good compromise between simplified methods of dynamic analysis and time domain analysis. The pseudo-static FE approach can accurately model the in situ, stresses prior to seismic loading (when it follows a static analysis simulating the construction sequence) is relatively simple and not as computationally expensive as the time domain approach. However this method should be used with caution as the results can be sensitive to the choice of the mesh dimensions. In this paper two simple examples of pseudo-static finite element analysis are examined parametrically, a homogeneous slope and a cantilever retaining wall, exploring the sensitivity of the pseudo-static analysis results on the adopted mesh size. The mesh dependence was found to be more pronounced for problems with high critical seismic coefficients values (e.g. gentle slopes or small walls), as in these cases a generalised layer failure mechanism is developed simultaneously with the slope or wall mechanism. In general the mesh width was found not to affect notably the predicted value of critical seismic coefficient but to have a major impact on the predicted movements. 相似文献
20.
The elasto-plastic analysis of a circular underground opening using the finite element method (FEM), the coupled finite element and the boundary element method (FEBEM) is presented. The coupling procedure and elasto-plastic formulation are discussed. The effect of in situ stress ratio on yielded zone, displaced shape and principal stresses is presented. The results of FEBEM analysis are compared with those obtained from FEM. The computation time and the number of iterations as required by FEBEM and FEM are compared. 相似文献