静力触探比贯入阻力与土体抗剪强度相关关系研究

发布时间：2018-09-12 11:41

【摘要】：随着城市化进程的加快,城市地下空间开发利用不断发展。深大基础工程增多,基坑开挖深度增加,工程规模增大,工程难度提高,对工程技术和科研水平提出了新的挑战。如何有效确定土体抗剪强度,准确进行基础稳定计算是关键问题之一。特别对于饱和软土地区的深基坑,难以测定施工期的孔隙水压力,通常要通过原位或室内固结不排水的剪切试验,测定破坏时的总抗剪强度进行总应力法分析。在众多原位试验中,静力触探仪是在不扰动土体原位状态的情况进行试验,具有设备简单、连续性好、数据可靠高等优点,在岩土勘察设计中应用广泛。建立静力触探比贯入阻力与土体抗剪强度相关关系,可以有效解决前述关键问题。而国内外又缺乏相关应用成果,本文通过理论、回归和数值方法研究其相关关系,研究内容和相关成果主要包括以下方面：首先,采用圆柱孔穴扩张理论推导了饱和软土中比贯入阻力与土体抗剪强度之间的关系。根据饱和软土假定,屈服准则,通过平衡方程,几何方程,本构方程以及边界条件求解给出了极限孔穴扩张压力,并得到土体弹塑性区的应力解、位移解及塑性区范围,给出圆柱孔穴扩张理论下静力触探比贯入阻力与土体抗剪强度相关关系式。其次,通过上海地区19个工程和武汉地区33个工程,共694组数据分不同土类对比贯入阻力与抗剪强度的相关关系进行研究,对两地区三种土的物理力学特性进行了分析总结,并经过回归分析确定分土类下可应用于相应地区工程的静力触探比贯入阻力与土体抗剪强度相关关系式。然后,基于自适应网格技术有限元大变形分析方法,对静力触探贯入过程进行模拟研究,土体位移随贯入深度增大而增大,贯入影响范围区向侧方和下方不断延伸。当锥头深入一定距离后,位移影响区趋近于环包状分布。阻力随抗剪强度的增大而增大,并根据锥头应力值得到比贯入阻力与抗剪强度的相关关系式。最后,结合上海地区典型工程世博演艺中心工程,对比分析了三种方法下确定土体抗剪强度的吻合性。认为孔穴扩张理论推导和有限元分析的条件理想化,忽略了土体固结、各向异性、摩擦性等特性。回归分析采用了当地的工程资料,综合了土体多方面特性,与实际土体抗剪强度吻合度较好。因此,在未建立多因素下通用表达式之前,根据工程资料确定静力触探比贯入阻力与抗剪强度相关关系是必要的,具有工程实用价值。另外,本文基于52个工程的勘察数据建立了静力触探相关资料数据库。结合目前的IT技术和软件对工程勘察资料数据库工作(数字化,标准化,数据库)做了初步探索研究。
[Abstract]:With the acceleration of urbanization, the development and utilization of urban underground space continues to develop. The increase of deep foundation engineering, the increase of excavation depth, the increase of engineering scale and the increase of engineering difficulty raise new challenges to engineering technology and scientific research level. One of the key problems is how to determine the shear strength of soil and calculate the foundation stability accurately. Especially for deep foundation pit in saturated soft soil area, it is difficult to measure pore water pressure during construction period, usually through in-situ or indoor consolidation undrained shear test, the total shear strength of failure is analyzed by total stress method. In many in-situ tests, the static penetration detector is used in the case of undisturbed soil in situ, which has the advantages of simple equipment, good continuity, high reliability and so on. It is widely used in geotechnical survey and design. The key problems mentioned above can be effectively solved by establishing the relationship between the specific penetration resistance and the shear strength of soil. However, there is a lack of relevant application results at home and abroad. In this paper, the correlation relationship is studied by means of theory, regression and numerical method. The research contents and related results mainly include the following aspects: first, The relationship between specific penetration resistance and shear strength of saturated soft soil is derived by using the theory of cylindrical cavity expansion. According to the assumption of saturated soft soil and yield criterion, the ultimate pore expansion pressure is obtained by solving equilibrium equation, geometric equation, constitutive equation and boundary condition, and the stress solution, displacement solution and plastic zone range of soil elastoplastic zone are obtained. The relationship between the penetration resistance of static penetration and the shear strength of soil under the theory of cylindrical cavity expansion is given. Secondly, through 19 projects in Shanghai and 33 projects in Wuhan, 694 groups of data are used to study the correlation between penetration resistance and shear strength of different soil types, and the physical and mechanical properties of three kinds of soils in two regions are analyzed and summarized. Through regression analysis, the relationship between the specific penetration resistance and the shear strength of soil is determined. Then, based on the finite element large deformation analysis method of adaptive mesh technology, the static penetration process is simulated. The soil displacement increases with the depth of penetration, and the penetration area extends to the side and below. When the cone head goes deep into a certain distance, the displacement-affected area approaches to the annular envelope distribution. The resistance increases with the increase of shear strength. Finally, combined with the typical project in Shanghai area, the consistency of shear strength of soil is compared and analyzed under three methods. It is considered that the theory of pore expansion and the condition of finite element analysis are idealized, and the characteristics of soil consolidation, anisotropy and friction are ignored. The regression analysis adopts the local engineering data and synthesizes the various characteristics of the soil, which is in good agreement with the actual shear strength of the soil. Therefore, it is necessary to determine the relationship between the specific penetration resistance of static penetration and shear strength according to engineering data before the establishment of a general expression under multiple factors, which is of practical value in engineering. In addition, based on the survey data of 52 projects, the database of hydrostatic penetration data is established in this paper. Combined with the current IT technology and software, this paper makes a preliminary exploration and research on the database work of engineering survey data (digitization, standardization, database).
【学位授予单位】：中国水利水电科学研究院
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU43

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