地震作用下多年冻土区低缓坡度滑坡发育机理研究
发布时间：2018-11-06 18:11
【摘要】：青藏高原是我国多年冻土分布的主要区域,同时也是我国地震最集中发生的地区。随着我国西部大开发战略的实施和深入,大型工程项目建设越来越多的在青藏高原兴起,此类工程的建设和维护也将越来越受到人们关注。因此研究多年冻土区斜坡在地震作用下的失稳机理是十分必要的,其研究成果将会对此地工程建设具有一定的影响意义。运用振动台等设备进行了多年冻土区斜坡的近似原型试验和数值模拟。通过对前人研究成果和试验段现场考察,设计并制作了多年冻土区低缓坡度斜坡近似原型的模型,采用反映青藏高原地震特点的人工合成地震波,完成了水平方向和垂直方向荷载下的大型振动台模型试验。研究指出地震作用下多年冻土区斜坡滑动是沿着冰土界面的软弱层整体滑动的,斜坡土体内部没有发生变形。斜坡破坏后其水平方向自振频率下降明显,垂直方向无明显变化。加速度沿斜坡高程具有放大效应,水平方向加速度放大效应大于垂直方向,在冰土界面软弱层加速度放大效应小于下部冰层和上部土体。冰土界面软弱层的孔隙水压力受水平方向地震荷载影响较大且在振动过程中变化明显。振动过程中上部土体的温度有所增加,冰土界面的水分含量逐渐增大。数值计算地震作用下此类斜坡的动力响应指出,随着地震荷载的增大,斜坡稳定的安全系数不断减小;振动过程中冰土界面孔隙水压力不断上升,当振幅较小时孔压上升不明显,振幅较大时孔压上升明显;斜坡的最大剪应变主要存在冰土界面软弱层中。综合考虑多年冻土区地震作用下斜坡破坏机理可认为冰土界面软弱层的存在是导致地震作用下斜坡沿冰土界面滑动的主要因素,振动过程中冰土界面超孔隙水压力的产生和冰土界面软弱层加速度减小而产生的剪力以及冰土界面软弱层含水量增大,都是诱发滑坡的因素。本次研究得到了中科院寒旱所冻土工程国家重点实验室开放基金(No.SKLFSE201209)的支持。
[Abstract]:Qinghai-Xizang Plateau is the main area of permafrost distribution in China, and it is also the most concentrated area of earthquakes in China. With the implementation and deepening of the strategy of western development in China, more and more large-scale engineering projects are springing up in the Qinghai-Tibet Plateau, and the construction and maintenance of such projects will be paid more and more attention to. Therefore, it is necessary to study the instability mechanism of slopes in permafrost regions under earthquake, and the research results will have a certain impact on the local engineering construction. The approximate prototype test and numerical simulation of slope in permafrost region were carried out by means of shaking table and other equipment. Based on the previous research results and field investigation of the test section, an approximate prototype model of low-gradient slope in permafrost region is designed and made. The synthetic seismic waves reflecting the seismic characteristics of the Qinghai-Xizang Plateau are adopted. The model tests of large shaking table under horizontal and vertical loads have been completed. It is pointed out that the slope sliding in permafrost region under earthquake is a whole sliding along the interface of ice and soil and there is no deformation inside the slope soil. After the slope failure, the natural vibration frequency of horizontal direction decreases obviously, but the vertical direction has no obvious change. The acceleration amplification effect along the slope height is larger than that in the vertical direction, and the acceleration amplification effect in the weak layer at the interface between ice and soil is smaller than that in the lower ice layer and the upper soil mass. The pore water pressure of the weak layer at the interface of ice and soil is greatly affected by the horizontal seismic load and changes obviously during the vibration process. During vibration, the temperature of the upper soil increases and the moisture content of the interface increases gradually. Numerical calculation of the dynamic response of this kind of slope under seismic action indicates that the safety factor of slope stability decreases with the increase of seismic load. During vibration, pore water pressure at the interface of ice soil is rising continuously, but pore water pressure increases obviously when the amplitude is small, and the maximum shear strain of slope mainly exists in the weak layer at the interface of ice and soil. Considering the mechanism of slope failure under earthquake action in permafrost region, it can be concluded that the existence of weak layer at the interface of ice and soil is the main factor leading to the slope sliding along the interface of ice and soil under earthquake. The formation of excess pore water pressure at the ice-soil interface, the shear force caused by the decrease of acceleration in the ice-soil interface weak layer and the increase of the water content in the ice-soil interface are all the factors that induce the landslide. The study was supported by the State key Laboratory of Frozen soil Engineering (No.SKLFSE201209) of the Institute of Cold and drought of the Chinese Academy of Sciences.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435;P642.22
本文编号：2315078
[Abstract]:Qinghai-Xizang Plateau is the main area of permafrost distribution in China, and it is also the most concentrated area of earthquakes in China. With the implementation and deepening of the strategy of western development in China, more and more large-scale engineering projects are springing up in the Qinghai-Tibet Plateau, and the construction and maintenance of such projects will be paid more and more attention to. Therefore, it is necessary to study the instability mechanism of slopes in permafrost regions under earthquake, and the research results will have a certain impact on the local engineering construction. The approximate prototype test and numerical simulation of slope in permafrost region were carried out by means of shaking table and other equipment. Based on the previous research results and field investigation of the test section, an approximate prototype model of low-gradient slope in permafrost region is designed and made. The synthetic seismic waves reflecting the seismic characteristics of the Qinghai-Xizang Plateau are adopted. The model tests of large shaking table under horizontal and vertical loads have been completed. It is pointed out that the slope sliding in permafrost region under earthquake is a whole sliding along the interface of ice and soil and there is no deformation inside the slope soil. After the slope failure, the natural vibration frequency of horizontal direction decreases obviously, but the vertical direction has no obvious change. The acceleration amplification effect along the slope height is larger than that in the vertical direction, and the acceleration amplification effect in the weak layer at the interface between ice and soil is smaller than that in the lower ice layer and the upper soil mass. The pore water pressure of the weak layer at the interface of ice and soil is greatly affected by the horizontal seismic load and changes obviously during the vibration process. During vibration, the temperature of the upper soil increases and the moisture content of the interface increases gradually. Numerical calculation of the dynamic response of this kind of slope under seismic action indicates that the safety factor of slope stability decreases with the increase of seismic load. During vibration, pore water pressure at the interface of ice soil is rising continuously, but pore water pressure increases obviously when the amplitude is small, and the maximum shear strain of slope mainly exists in the weak layer at the interface of ice and soil. Considering the mechanism of slope failure under earthquake action in permafrost region, it can be concluded that the existence of weak layer at the interface of ice and soil is the main factor leading to the slope sliding along the interface of ice and soil under earthquake. The formation of excess pore water pressure at the ice-soil interface, the shear force caused by the decrease of acceleration in the ice-soil interface weak layer and the increase of the water content in the ice-soil interface are all the factors that induce the landslide. The study was supported by the State key Laboratory of Frozen soil Engineering (No.SKLFSE201209) of the Institute of Cold and drought of the Chinese Academy of Sciences.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435;P642.22
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