【作者】 张海东；

【导师】 言志信；

【作者基本信息】 兰州大学 ， 防灾减灾工程及防护工程， 2012， 硕士

【摘要】 我国黄土分布广泛,特别是位于乌鞘岭与太行山之间的黄土高原地区,黄土堆积厚度大,天然地貌沟壑纵横,存在大量的天然黄土边坡,随着黄土高原地区的开发建设,伴随而来的是大量人工黄土边坡的产生；我国地震灾害严重,黄土高原地区为地震多发区。由于黄土颗粒成分多、结构疏松,历史上因地震诱发的黄土边坡滑坡数目庞大;黄土边坡动力响应研究已经成为工程建设中亟待解决的问题,该方面的研究目前尚不完善,因此,开展黄土边坡动力响应研究具有重要意义。本文利用FLAC3D有限差分软件对多层黄土边坡进行动力响应数值分析。主要研究了边坡土层组成对地震波的传播及对边坡自由面加速度峰值放大作用的影响；探讨了常见黄土边坡因土层参数变化,对边坡地震加速度响应及稳定性的影响,采用FLAC3D有限差分软件模拟计算了黄土常见的洞穴对黄土边坡动力响应的影响。(1)双层模型和三层模型计算结果表明：当坡体位于基岩之上时,其塑性区较单层均质边坡均会出现扩大现象,当材料参数较小时会产生一个贯通的滑移面,而当材料参数较高时,剪应变率较大值区域只出现在坡脚处,呈向坡内发展的半圆形,坡体的受拉-剪破坏区随坡体材料参数的降低而向坡内扩展。(2)不同层数黄土边坡动力响应研究结果表明：PGA放大系数在坡顶最大,在坡脚处较大,最小值则出现在坡高1/3至1/2处；多层边坡情况下,PGA放大系数下降段的下降幅度会发生减小现象,坡体内较小洞穴的存在使坡面水平向PGA放大系数发生增大现象,坡面竖向PGA放大系数在坡面中下部增大、在坡面中上部减小的现象(3)坡内下部存在洞穴时,使坡内受拉-剪破坏区向坡内转移,拉破坏区深度增大,从洞穴沿斜向上方向至坡面区域内发生拉破坏现象；坡内剪应变率较大值区域沿潜在滑移面向坡顶扩展。坡内中部存在洞穴时,致使坡内潜在滑移面上的剪应变率较大值区域通过洞穴与坡面贯通,使边坡发生局部破坏甚至失稳。坡内顶部存在洞穴时,对边坡整体应力分布及位移影响较小,只对局部产生影响。更多还原

【Abstract】 Loess topography is widely distributed in China,especially in the area of loess plateau between Wushaoling and Taihang Mountains.In this area,the accumulation thickness of the loess is very large and the natural landscape is rugged.With the development of the exploitation of loess area,a large number of aritificial loess slopes come into being.Our country is a harder-hit earthquake area,and the loess plateau area is an earthquake-prone one.Since the composition of the loess grains arevery complex and the structure is loose,there were a large number of loess slopes induced by the earthquake in history.Analysis of multi-layer loess slope’s dynamic response is now a very important problem which requires immediately solution.And researches about this are imperfect,so the subject of this paper is of great significance.This paper analyses the Dynamic response of multi-layer loess slope,using the FLAC3D finite difference software.It mainly analyses the composition of the slope’s soil layer’s effects on the transmission of seismic wave and the slope’s free surface’s effects on the amplification of acceleration.It also researches common loess slopes’effects on the response and stability of slope earthquake acceleration and calculates the effects of common loess cave on the stability of the loess slope via the finite difference numerical simulation.(1) Calculations of two-layer model and three-layer model indicate that:Compared to single inhomogeneous slope,it’s plastic zones amplify when the slope is on the bedrock.When the material parameter is small, it will produce a interconnected glide plane.While material parameter is high,the plastic zone only appears at the point of the slope toe and it presents as a semicircular towards the inside of the slope.And the slope’s tension-shear failure zone expands towards the inside of the slope with the reduction of the material parameters.(2) Dynamic response results of different layers of loess slopes show that:the PGA amplification factor comes to the maximum at the top of the slope,it gets to the median at the slope toe,and the minimum appears from1/3to1/2of the height of the slope.Under this circumstance of multi-layer loess slopes,the descending range will decrease during the descending branch of the PGA amplification factor.The smaller caves inside of the slope make the horizontal PGA amplification factor increase.And the PGA amplification factor increases at the lower part of the slope and decreases at the upper part.(3) When caves exist at the lower part of the inside of the Slope, the tensile shear failure zone shifts to the inside of the slope.The damage depth increases.Tensile failure appears in the area form the cave to the slope surface along the diagonal direction.The plastic zone inside of the slope expands towards to the top of the slope along the latent glide plane.When caves exist at the middle part of the inside of the Slope, the plastic zone on the latent glide plane is connected with the slope surface through the caves.It will damage the slope partially and even destroy the stability.And When caves exist at the top of the inside of the Slope,it has little effects on stress distribution of the whole slope and the displacement,it only affects partially.更多还原