合肥地区膨胀土大围压下三轴强度特性试验研究

发布时间：2019-02-15 01:15

【摘要】：随着国家经济建设的发展,城市化建设程度的加快,人口向大中城市迁移和集中。合肥市作为安徽省的省会、长江三角洲的副中心城市及国家首个高新创新中心。为满足这种发展的需求,合肥市建筑物的高度和密度不断增大,同时为解决城市交通拥堵的问题,地下交通—地铁的建设也在全市全面铺开。在这些工程中,土体常常处于较大的围压作用状态。目前,针对这类土体的强度和稳定计算,由于受到试验仪器的限制,仍多采用常规三轴试验指标,这显然与工程土体所处的应力状态不符。因而,对合肥市的土体(主要是膨胀土),开展超过常规围压的大围压三轴试验,对土体的抗剪强度指标进行试验研究,获取强度参数指标,对处于大围压状态的土体强度和稳定性计算,提供科学依据。(1)按照试验仪器所能承受的围压试验值,将试验围压分为三个围压段进行试验。即100~300kPa为常规围压段,600~800kPa为中围压段,1100~1300kPa为大围压段。为保证试验结果的一致性,在同一基坑中获取试验土样280个,有效试验225个。(2)三个围压段,分别进行不固结不排水(UU)、固结不排水(CU)、固结排水(CD)三轴试验。试验显示随着围压的增大,土体的强度呈现衰减的趋势;土样随着固结和排水条件的变化,强度衰减幅度不同,按不固结不排水(UU)、固结排水(CD)、固结不排水(CU)顺序衰减逐渐减弱。(3)对三个围压段,以相同固结和排水条件的三轴试验破坏莫尔圆画出莫尔包络线,并对其进行拟合研究,得出合肥市膨胀土中、大围压下莫尔包络线的基本线型。不固结不排水(UU)为抛物线型,固结不排水(CU)与固结排水(CD)为二次对数型,为合肥地区中、大围压土体的强度指标的工程选取和应用提供借鉴。
[Abstract]:With the development of national economic construction and the acceleration of urbanization, the population migrates and concentrates to large and medium cities. Hefei is the provincial capital of Anhui Province, the sub-center city of the Yangtze River Delta and the country's first high-tech innovation center. In order to meet the demand of this kind of development, the height and density of the buildings in Hefei are increasing, and in order to solve the problem of urban traffic congestion, the construction of underground transports-subway is also spread out in the whole city. In these projects, soil is often in a larger confining pressure state. At present, for the strength and stability calculation of this kind of soil mass, because of the limitation of the test instrument, the conventional triaxial test index is often used, which obviously does not accord with the stress state of the engineering soil mass. Therefore, the large confining pressure triaxial test is carried out on the soil mass (mainly expansive soil) in Hefei, and the shear strength index of the soil is studied, and the strength parameter index is obtained. Scientific basis is provided for the calculation of strength and stability of soil in the state of large confining pressure. (1) according to the experimental value of confining pressure which the test instrument can bear, the test confining pressure is divided into three confining pressure sections. That is, 100~300kPa is the normal confining pressure, 600~800kPa is the middle confining pressure, and 1100~1300kPa is the large confining pressure. In order to ensure the consistency of the test results, 280 test soil samples were obtained in the same foundation pit, and 225 effective tests were conducted. (2) three confining pressure sections were carried out respectively for unconsolidated undrained (UU), consolidation and undrained (CU),. Consolidation drainage (CD) triaxial test. The results show that the strength of soil decreases with the increase of confining pressure. With the change of consolidation and drainage conditions, the intensity attenuation ranges of soil samples are different, and the attenuation of unconsolidated undrained (UU), consolidation and drainage (CD), consolidation and undrained (CU) gradually decreases. (3) for three confining pressure sections, The moire envelope line is drawn by triaxial test with the same consolidation and drainage conditions, and the basic shape of moire envelope line is obtained under large confining pressure in expansive soil of Hefei. The unconsolidated undrained (UU) is a parabolic type, and the consolidation undrained (CU) and consolidated drainage (CD) are quadratic logarithmic, which provides a reference for the engineering selection and application of the strength index of the large confining pressure soil in Hefei area.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU443

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