用于三维复杂土坡稳定性分析的滑动面搜索新方法

【作者】 邓东平；

【导师】 李亮；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2010， 硕士

【摘要】 本文提出利用随机角来生成随机滑动面的一种新方法,通过研究随机曲线的生成规律,将二维随机滑动面的搜索简化成不同角度和竖直土条划分相结合而生成的近似曲线的搜索。针对新方法在边坡坡面外形复杂、各种层状的非均质土层和水参与下遇到的一些不同情况采取了一些基本方案(包括整体稳定性和局部稳定性),并将滑动面搜索新方法应用于均质土坡、分层土坡和稳定渗流作用下的土坡稳定性分析。然后,在考虑边坡几何外形、土层参数和边坡水位变化三种情况时,对边坡可能存在的局部稳定性进行了研究。为了拓展二维滑动面搜索新方法的应用,将单一曲线滑动面进行改进,提出了多段曲线滑动面搜索新方法并将应用于分层土坡中；提出了折线滑动面搜索新方法并将其应用于坡面外形复杂的土坡。通过以单一曲线滑动面搜索新方法为基础,提出了由母线和准线生成三维任意滑动面的新方法,并就工程上滑动体非对称情况(包括准线不对称和长度不对称)、母线不在滑动体内沿滑动方向断面尺寸最大的面上、土坡含软弱夹层的情况,提出了解决措施,将其应用于三维简单均质土坡和工程上常见的填挖方复合土坡、水平分层填方路堤、公路纵断面为平斜坡的土坡和含软弱夹层的土坡这四种复杂土坡算例中。通过对比计算与分析,获得了如下研究成果：(1)通过各种实例对比与分析,可得出新方法在均质土坡、分层土坡或有稳定渗流作用下的土坡中(包括边坡的整体稳定性或局部稳定性),计算出的安全系数与以往研究成果颇为接近,但得到的最危险滑动面与实际情况更为相符,因而可说明新方法的可行性；(2)稳定渗流作用下土坡的稳定性分析中,以非圆弧滑动面计算得到的结果较以圆弧滑动面得到的结果更为可靠,随着土坡坡内地下水位的升高,计算出的安全系数急剧下降,因而渗流效应会成为边坡发生失稳的一个重要因素；(3)在土坡的整体稳定性和局部稳定性中,边坡的几何外形、土层之间的差异、坡内外水位及土层的材料参数γ、c和φ的变化对土坡可能出现的局部失稳影响较大,但是φ与c的无量纲之比的减小可能使土坡转为整体稳定性；(4)在分层土坡中,计算出的安全系数以分段曲线滑动面方法最小,其次是单一曲线滑动面方法,圆弧滑动面方法最大。而从得到的临界滑动面的结果来看,当土层间材料物理性质相差较大时,其滑动面表现为非圆弧性,且各土层间的滑动面也不完全一致,可说明分段曲线滑动面新方法能够得到更接近于实际情况的最危险滑动面；(5)对三维土坡问题进行研究,可知：①在同一土坡中,土坡的三维稳定性高于二维稳定性性；②当填挖边坡上填方段和挖方段的材料不一致时,更容易在抗滑稳定性差的材料处发生失稳,但在填方段和挖方段的材料重度γ相同时,两种材料的φ／c是否相等在一定程度上对滑动体的对称性和大小有影响；③对于公路纵断面为平斜坡的土坡,其潜在最危险滑动面更倾向于平坡段,斜坡对边坡的稳定有一定的积极影响；④在含软弱夹层的土坡中,当滑动体的长度无限长时,其三维稳定性趋于二维稳定性。其中,本文创新点如下：(1)本文方法较新颖,不仅能够适用于土坡的二维和三维稳定性分析,而且能够较容易地在计算机上编程实现安全系数的计算和滑动面图形的绘制；(2)用本文新方法通过实例分析讨论了含软弱夹层土坡的滑动面型式选择(软弱夹层的存在对滑动面型式的选择有影响),得到了其滑动面的一般模式；(3)考虑渗流效应时,将竖直土条视为三种划分情况,并分别进行受力分析,推导出简化Janbu法中土条的浮力和渗透力计算公式。更多还原

【Abstract】 This article puts forward a new method of using random angle to generate random sliding surface, and by studying generation law of random curves search of two-dimensional random sliding surface was simplified into search of approximate curve generated by combination of delineation of different angles and vertical soil slices.Some basic solutions were provided under a number of different circumstances of slopes with complicated shape,a variety of heterogeneous layered soil and water encountered (including the general stability and local stability) in new method. And the new method of search of sliding surface is applied to homogeneous soil slope, stratified slopes and slopes under action of seepage.Then, considering three cases of slope geometry, soil parameters and change of water level in slope, possible of local stability of slope was studied.At the same time,for expanding application of the new method of two-dimensional sliding surface search, through improving new method of a single curve sliding surface search the new methods of multi-segment curve sliding surfaces search and line sliding surfaces search was proposed, and apply them in stratified soil and soil slope with complex shape respectively.As a basic of the new method of a single curve sliding surface, a new method of arbitrary sliding surface generated by mother line and standard line is proposed.For the sliding body of asymmetry in the engineering (including the case of standard line of asymmetric and length of asymmetric) and mother line being not in the largest cross-section of the sliding body along the sliding direction, and slopes with weak interlayer, some solution measures are used.Then these are applied to three-dimensional simple homogeneous slopes and four examples of common excavation and filling compound slope in the engineering, filling embankment at form of hierarchical Level,vertical section of road with flat and oblique slope and the slopes with weak interlayer.By contrast and analysis of calculating, the following conclusions can be obtained. (1)Through comparison and analysis of various examples, it can be obtained that in homogeneous soil, layered soil or soil under steady seepage (including the overall slope stability or local stability), factor of safety calculated by using new method is quite close to previous research, and the critical sliding surface got by using new method is consistent with the actual situation. Therefore those demonstrate the feasibility of the new method.(2) On stability analysis of slope under effect of seepage,the calculated results with non-circular sliding surface are more reliable than with circular sliding surface, and with increase of groundwater level in slope factor of safety of slopes were sharply decline, so effect of seepage is an important factor for occurring of slope instability.(3) In general stability and local stability of slopes,changes of slope geometry, difference between soil, water level in outside and inside of slope and soil material parameters y, c andφchanges may impact occurrence of local instability of slopes, but decrease of dimensionless ratio ofφand c may turn to general stability of slopes.(4) In the layered soil,comparing with factor of safety, the result of multi-segment curve sliding surface method is minimum, followed by single curve sliding surface method, and that of circular sliding surface method is the largest, at the same time from the results of critical sliding surface obtained, while physical properties between soil have large difference, sliding surface performs non-circular arc, and sliding surface between soil is also not entirely consistent, so those can illustrate that multi-segment curve sliding surface method could get closer to actual situation of the critical sliding surface.(5)Research on problems of three-dimensional slope showed that firstly three-dimensional stability is higher than two-dimensional stability in the same slopes and secondly when the fill material and excavation material is inconsistent in excavation and filling compound slope, the sliding instability occurs easier at poor stability of materials, but at the case of material of filling and excavation with same severe y, whetherφ/ c of two materials is equal impacts symmetry and size of the sliding body on a certain extent, and thirdly for the slope of vertical section of road with flat slope, the most potential dangerous sliding surface is more inclined to flat slope section of the slope and oblique slope section of the slope have some positive impact on the slope stability, and fourthly in slope with weak interlayer, when the length of sliding body reaches infinite length its three-dimensional stability tends to two-dimensional stability.In this article there are some innovations as follows:(1)The method of this article is relatively new, and that can not only be applied to stability analysis of two-dimensional and three-dimensional slope,but also easily calculate factor of safety and draw graphics sliding surface through programming in computer.(2) An example of soil slope containing soft interlayer (existence of weak interlayer impact the choose of type of sliding surface) is discussed and analyzed in type selection of sliding surface by using new method, and obtain general calculations model of sliding surface in this case.(3)When considering the effect of seepage, soil slices was seen as three kinds of division and conducted mechanical analysis to derive the formula of buoyancy and penetration of slices in simplified Janbu method respectively.更多还原