温湿度循环下非饱和松散堆积体的剪切特性研究

发布时间：2018-06-26 19:11

本文选题：非饱和 + 堆积体　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：在汶川大地震的震中区域映秀镇,地震引起山体破碎,形成大量的松散堆积体边坡,雨季到来时经常发生滑坡和泥石流等自然灾害,严重影响着人民的生命财产安全。大量的现有研究表明温湿度对土的剪切特性有较大影响,但大部分研究对象为黏土。温湿度循环下松散堆积体的剪切特性研究目前还没有进行过,故此研究将为非饱和松散堆积体边坡的稳定性分析提供重要的数据参考,且对其破坏的预测和防护具有重要的指导意义。本文试验用土采用映秀镇现场堆积体,分别对温度循环和干湿循环后的非饱和松散堆积体进行了大型三轴剪切试验,并对其剪切特性受温湿度影响规律进行了总结和分析。针对粗颗粒松散堆积体剪切的要求,本文自主设计制作了一整套大型非饱和三轴仪;针对温度循环的试验要求,本文提出了控制试样温度的试验方案,即通过控制压力室水温来控制试样温度;针对干湿循环的试验要求,本文提出了干燥试样的试验方案,即采用向试样内部通热气的方法来干燥试样并进行试样吸力测量。在排水条件下,升温导致高围压下饱和试样收缩,这主要是由于试样中孔隙体积减小导致的,而低围压饱和试样发生轻微热膨胀,这主要是由于试样中土颗粒自身热膨胀导致的;升温导致了饱和试样剪切强度的提高及有效内摩擦角的增大。在排水条件下,温度循环导致饱和试样收缩,且温度循环后饱和试样的初始弹性模量、剪切强度和有效内摩擦角均有所提高。在排气条件下,非饱和试样在加热过程中吸力大幅减小且体积收缩,在加热后剪切强度有所降低且表现为更小的脆性,剪切强度随吸力而增大的速率大幅减小。在排气条件下,非饱和试样在温度循环后初始吸力小幅减少且体积收缩,剪切强度小幅增大。在室温条件下的常含水率三轴试验中,低初始吸力试样在剪切阶段吸力以增大为主,高初始吸力试样在剪切阶段吸力以减小为主,破坏更早且脆性更大。在室温条件下,非饱和试样在干燥和湿润过程均发生体积收缩,在干湿循环后表现出更大的剪胀和更大的脆性,且剪切强度不变。
[Abstract]:In Yingxiu Town, the epicenter of Wenchuan earthquake, the earthquake caused the breakage of mountain body and formed a large number of loose accumulative slope. When the rainy season came, natural disasters such as landslide and debris flow often occurred, which seriously affected the safety of people's life and property. A large number of existing studies show that temperature and humidity have a great impact on the shear characteristics of soil, but most of the research objects are clay. The shear characteristics of loose deposits under temperature and humidity cycles have not been studied, so the study will provide an important data reference for the stability analysis of unsaturated loose deposits slope. And the prediction and prevention of its damage have important guiding significance. In this paper, the large scale triaxial shear tests of the unsaturated loose accumulations after temperature cycling and dry and wet cycling are carried out in Yingxiuzhen by using the in-situ accumulations in Yingxiu Town, and the shear characteristics affected by temperature and humidity are summarized and analyzed. According to the requirement of coarse grain loose accumulation body shear, a set of large unsaturated triaxial apparatus is designed and manufactured by ourselves, and the test scheme of controlling sample temperature is put forward according to the test requirement of temperature cycle. According to the test requirement of dry and wet cycle, the test scheme of drying sample is put forward, that is to say, the method of heating air into the sample is adopted to dry the sample and measure the suction of the sample. Under the drainage condition, the temperature rise results in the shrinkage of the saturated specimen under high confining pressure, which is mainly due to the decrease of pore volume in the sample, while the slight thermal expansion occurs in the saturated specimen with low confining pressure. This is mainly due to the thermal expansion of the soil particles in the sample and the increase of the shear strength and the effective internal friction angle of the saturated sample. Under the drainage condition, the temperature cycle results in the shrinkage of the saturated specimen, and the initial elastic modulus, shear strength and effective internal friction angle of the saturated specimen are increased after the temperature cycling. Under the condition of exhaust, the suction and volume shrinkage of unsaturated specimen decrease greatly during heating, and the shear strength decreases and appears to be smaller brittleness after heating, and the rate of shear strength increases with suction decreases significantly. Under the exhaust condition, the initial suction decreases slightly and the volume shrinks, and the shear strength increases slightly after temperature cycling. In the triaxial test of constant moisture content at room temperature, the suction of low initial suction specimen is mainly increased in shear stage, while that of high initial suction sample is decreased in shear stage, and the failure is earlier and brittleness is greater. At room temperature, the volume of unsaturated samples shrinks during drying and wetting, and exhibits greater shear expansion and brittleness after drying and wet cycling, and the shear strength is constant.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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