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地震作用下碎石土斜坡损伤特性与破坏模式研究
Alternative TitleStudy on damage characteristics and failure modes gravel of soil slope under seismic load
Language中文
邱洪志
Thesis Advisor孔纪名
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name博士
Degree Discipline岩土工程
Keyword地震 损伤坡体 碎石土坡体 损伤特性 破坏模式 稳定性分析
Other Abstract

汶川地震发生在龙门山断裂带上,区域内地质条件极其复杂且碎石土坡体广泛分布。地震使坡体产生不同程度的变形,引发了数以千万计的次生山地灾害,特别是地震斜坡失稳破坏造成的灾害令人触目惊心。地震发生之后,通过调查大量灾害的分布及成因发现,地震对碎石土斜坡的影响不仅仅表现在地震过程中,其发生之后若干年内,受地震影响的区域仍会出现滑坡及其它形式的灾害。因此研究强震触发滑坡的动力学机理与形成过程对认识山地灾害和灾害防治都具有重要的意义。本文以北川县鼓儿山不稳定斜坡及滑坡实例为基础,建立地质体分析模型,借助物理模型试验、数值模拟等手段,对地震荷载作用下碎石土斜坡的损伤特性及其破坏机理展开研究。研究了地震荷载的加速度幅值、持时及斜坡形态对坡体内部应力场、位移场、速度场和加速度场的影响规律;同时,在物理模型试验研究过程中,记录坡体内裂纹的演变过程,分析坡体内部和表面出现的裂纹的分布形态与基本特征,得到表征斜坡损伤程度的损伤状态参数。取得的研究成果如下:(1)假定损伤材料微元体的有效弹性模量服从Weibull分布模型。基于岩土材料破坏概率函数,建立起损伤材料的统计本构关系,并介绍了统计本构关系中各参数的确定方法。(2)利用数值分析方法和物理模型试验方法,分析了地震荷载参数与坡体形态参数对地震作用下碎石土坡体动力响应的影响规律。结果表明,①地震荷载加载过程中,坡体内部产生的应力与应变是动态变化的。加载开始阶段,产生的应变随持时逐渐增加,达到某一值后,应变不在继续增大而是随时间往返变化。②模型中相同位置的不同高度,从下往上应变幅值逐渐减小;同一高度,不同位置,模型中部产生的应变最大,其次是模型后部,最小的是模型前部。③随着地震持续时间的增加,模型后部和前部土体表面下沉,中部略微隆起;模型前部的坡体产生向外凸起的变形。地震加速度越小坡体表面变形越小,当加速度增大到一定值时,坡体表面沉降不再增加。增大模型的倾角,模型前部土体表面变形加剧,部分地方出现剪出破坏。(3)地震加速度的大小对放大效应的影响相对较小,高程对坡体地震加速度具有十分明显的放大效应。随高程的增加,水平加速度放大系数呈非线性增加。相同地震加速度作用下,地震加速度放大系数随高程的增加而增大,当高程超过模型中部时,随高程的增加,地震加速度放大系数增幅变快。相同地震荷载下,竖直方向响应加速度放大系数要比水平方向加速度放大系数小。(4)数值分析结果表明,地震荷载作用下碎石土坡体内剪切塑性区和拉伸塑性区最早出现在坡脚位置。随着地震荷载持续时间的增加,剪切塑性区从坡脚往坡体上部发展,坡顶位置的拉伸塑性区面积逐渐增加。拉伸塑性区是从坡体浅表层开始向着坡体深层发展,塑性区的面积逐渐增大,进而相互连通形成潜在滑动面。(5)通过物理模型试验,研究了地震荷载下碎石土坡体内裂隙、裂纹的几何形态与分布特征。归纳出地震作用下碎石土坡体内裂隙演化过程为,在地貌转折的位置首先出现裂隙~部分裂隙进一步扩展形成主裂缝~开始出现的主裂缝逐渐变宽~同时周围出现多条细裂纹~细裂纹进一步发展~并相互贯通~最终在坡体内部形成潜在的滑动面。 (6)碎石土斜坡在地震荷载作用下的破坏模式基本类型大致可分为三种:(1)拉裂-倾倒破坏;(2)崩解-滑落破坏;(3)滑移-拉裂破坏。(7)采用Bishop对安全系数的假定,同时考虑地震作用及岩土体材料损伤变量对坡体岩体强度的影响,推导出了坡体安全系数的计算方法,通过迭代的方法可以求出损伤坡体的安全系数。

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The “5.12” Wenchuan earthquake occurred in the Longmen Mountain Fault Zone, where the regional geological condition is very complex and there are lots of the gravel soil slope in near zone. the slope has the different degree of deformation induced by Earthquake, and which caused tens of millions of secondary mountain hazards, especially seismic slope instability caused by the disaster is shocking. After the earthquake, through the distribution and origin of the survey a lot of disaster found that the impact of an earthquake on gravelly soil slope lies not only in the earthquake process, after its occurrence within a few years, by the earthquake affected areas will still be disasters of landslide and other forms.Therefore, it is of great significance to study the dynamic mechanism and formation process of landslide triggered by strong earthquake.This paper based on Guer mountain unstable slope and landslide in Beichuan County, the geological model was established. By the means of all physical model test, numerical simulation, damage characteristics and failure mechanism of gravelly soil slope is studied under seismic load. Focus on the influence of earthquake on dynamic response of gravel soil slope, such as stress field, displacement field, speed field and the acceleration field. At the same time, in the physical model test and research process recorded the evolution of crack in the inner part of the slope, analysis of slope and surface crack distribution and basic characteristics, indicating the damage level of the slope parameter of damage state. The results obtained are as follows:(1) Assume that the effective elastic modulus of the material damage element obeys Weibull distribution model. Based on the failure probability function of rock and soil materials, the statistical constitutive relation of damage materials is established, and the method of determining the parameters in statistical constitutive relation is introduced.(2) Using the numerical analysis method and physical model test method, the influences of the seismic load parameters and slope shape parameters of earthquake gravel soil slope dynamic response are analyzed. The results show that the stress and strain generated in the slope body are dynamic in the process of earthquake loading. At the beginning of the loading, the strain increases gradually with the increase of time. After reaching a certain value, the strain will not continue to increase but change with time. In the model, the different height of the same position, from bottom to top, should be gradually reduced; the same height, different position, the maximum strain generated in the middle of the model, followed by the back of the model, the smallest is the front part of the model. With the increase of the duration of the earthquake, the rear and front of the model soil surface subsidence, the middle of a slight uplift; model of the front of the slope of the deformation of the outward bulge. The smaller the earthquake acceleration, the smaller the surface deformation of the slope, when the acceleration is increased to a certain value, the surface of the slope is no longer increased. Increasing the inclination of the model, the deformation of the soil surface in front of the model is increased, and the shear failure occurs in some areas.(3) The effect of seismic acceleration is relatively small on the amplification effect of seismic wave, and the height of the seismic acceleration has a very obvious amplification effect. With the increase of elevation, the horizontal acceleration amplification coefficient increases. Under the same seismic acceleration, the seismic acceleration amplification factor increases with the elevation, when the elevation exceeds the middle of the model, with the increase of the elevation, the seismic acceleration amplification factor increases rapidly. Under the same seismic load, the vertical response acceleration amplification factor is smaller than the horizontal acceleration amplification factor.(4) The numerical analysis results show that under the action of earthquake load gravel soil body shear plastic zone and tensile plastic zone appears most early in the location of the slope angle. With increase of the duration of the seismic load, shear plastic zone from the foot of the slope to slope top and position of slope of tensile plastic area gradually increased. The tensile plastic zone is from the shallow surface layer of the slope surface, and the area of the plastic zone increases gradually, and the potential sliding surface is connected with each other.(5) Based on the physical model test to study the seismic gravel slope body fracture, crack geometry and distribution characteristics. Summed up the earthquake rubble slope of fractures in process of evolution, in geomorphic turning position of the first cracks appeared ~ crack part of further expansion form the main crack ~ began to appear the main crack is gradually widened ~ also appeared around a plurality of small crack ~ fine cracks further development ~ and interconnected ~ and eventually the potential slip surface are formed within the body of the slope.(6) Study on failure mode of the gravelly soil slope suffered seismic load, the results show that the basic types of mode can be broadly divided into three: (1) - fracturing toppling failure; (2) disintegration - slide destruction; (3) slip tensile damage.(7) By the Bishop of stability coefficient assumed, at the same time, consider the effect of earthquake and geotechnical material damage variable of slope rock mass strength derived the stability coefficient of slope calculation method (as shown in following expressions), damage the slope stability coefficient are obtained through an iterative method. 

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18981
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
邱洪志. 地震作用下碎石土斜坡损伤特性与破坏模式研究[D]. 北京. 中国科学院大学,2016.
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