|Alternative Title||Study on damage characteristics and failure modes gravel of soil slope under seismic load|
|Place of Conferral||北京|
|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|
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.
|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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