【作者】 孙如华；

【导师】 李文平；

【作者基本信息】 中国矿业大学 ， 地质工程， 2010， 博士

【摘要】 东部矿区深部土以第三系土为主,该土层含水量低、致密、呈饱和坚硬或半坚硬状态,为一种土向软岩过渡的特殊土。近年来深井土层地压、渗漏问题日益突出,要彻底解决这一技术工程难题,必须深入研究深部土地质成因、结构、力学性、渗透性等工程地质性质。因此研究深部土结构力学性具有重要理论意义和实用价值。论文以东部矿区埋深300m以下深部土为研究对象,以室内试验、理论分析为主要研究手段,对深部土的微观结构特征、高压三轴卸载结构力学性以及高压K0固结等进行了较为深入、系统的研究。对深部土微观结构进行SEM探测,并且探索出一种简易可行的、大众化的影像图分析处理方法,提取了土体微观结构各结构要素信息;应用数理统计分析,对微观结构各单因素指标进行综合量化,得到了一个相对比较合理的反映深部粘土微观结构的综合量化参数S,结合密度ρ、含水量ω,建立了三者间的关系式。考虑近似模拟深部粘土天然和建井作用受力状态,利用MTS815电液伺服试验系统,进行深部原状土和重塑土高压三轴卸载试验研究,分析了土样经历从高压密实结构状态卸载到一较松散结构状态的应力-应变特征。应用GE8800CT机进行高压三轴卸载土体内部结构的CT探测,研究表明:土样初始状态时颗粒及孔隙排列定向性不明显;各向等压加压过程中,土颗粒明显密集,孔隙减少,且颗粒及孔隙排列趋于有序;轴压不变,围压卸载时砂土样横断面上土颗粒密度减小,孔隙增大,粘土样土颗粒密度基本保持不变,土样破坏时对横断面上土颗粒及孔隙定向性排列稍有影响。设计加工了固结压力可达18MPa的高压K0固结装置,进行了一土多样不同高压载荷K0固结试验,研究表明深部土体的特性与浅部土体明显不同,随着固结压力的增加,土样微观结构排列的各向异性逐步增加,当固结压力达到一定时,微观结构的各向异性增长幅度很小,说明土体内颗粒排列的方向性基本不再变化,颗粒高度定向,在宏观上表现则是K0值基本保持不变。三轴加载渗透试验表明:深部粘土原状土样渗透性存在明显的各向异性,同等轴向应力下垂直方向渗透系数kT小于水平方向渗透系数kH,突变前(即各自均未达到临界应力段)kH/kT大约在1.1-1.3之间,其原因主要是:扁平状的粘粒在垂直方向和水平方向不同应力环境下定向沉积,造成孔隙的水平方向导通性普遍优于垂直方向。利用高压K0计算公式分析水平地压对井壁稳定性的影响,较好的模拟实际工程状况,对井筒建设具有一定的指导意义。该论文有图48幅,表34个,参考文献195篇。更多还原

【Abstract】 The deep soils of mine area in eastern China are dominated by Tertiary soil layer, which contains low water content, is compact and appears in a saturated hard or half-hard condition, and is a type of special soil transitioning from soil to soft rock. In recent years the problems of earth pressure and permeation of deep well soil layer are outstanding, whereas it is required to look into the mechanical properties of engineering geology such as geological formation, structure, mechanics, permeability etc. of the deep soils in order to thoroughly solve such technical engineering difficulty. Therefore, the study the structural mechanics of deep soils has important theoretical significance and practical value.In this paper the soils buried below 300m in the mine area are taken, on the basis of indoor tests and theoretical analysis, and the micro-structural features, high Pressure triaxial unloading mechanical properties and K0 consolidation of the deep soils are studied deeply and systematically.Firstly, the microstructure of deep soils is detected by SEM, and a simple and feasible image map processing methods which can be extracted various micro-structural elements in deep soils are explored.Mathematical statistics is adopted for determining the weight of each single-factor index of the microstructure.And a relatively reasonable composite quantification parameter S that reflects the microstructure of deep clay is established. The densityρ, water contentωand composite quantification parameter S is , tcombined and he relationship among the parameters is established.Under the condition that considers approximate simulation of natural and well-building acting stress of deep clay,MTS815 servo test apparatus are introduced to carry out high Pressure triaxial unloading tests of undisturbed and remodeling soils, And the stress - strain characteristics through the state from high Pressure unloading dense structure to a more loose structure are analyzed.GE8800CT is introduced to detect high Pressure triaxial unloading soils. It is showed that: the initial state, the densities of different soil layers are close, and the arrangement of particles and pores inside the soil layer is not uniform; under the condition of equal pressure in all directions, the particle density of each soil layer increases, the pores decrease, the arrangement of the soil particles and pores tend to be uniform with the increase of pressure.When the confining pressure unloading is carried out and the axial pressure is kept unchanged, the particle density decreases and the porosity increasesof the sandy soil on the lateral section.But the particle density of the clay on the lateral section is basically kept unchanged.The directionality of particles and pores of the soil on the lateral section will be slightly influenced.A high Pressure K0 consolidation Apparatus which consolidation pressure up to 18MPa is designed.After K0 consolidation tests.We obtained that the remarkable difference between characteristic of deep soils mass and shallow soil mass. With the increase of consolidation pressure, soil samples ordered microstructure anisotropy gradually increasing,when the consolidation pressure to reach certain values, the microstructure anisotropic growth rate is small, indicating the direction of arrangement of soil particles does not change, the basic particles highly directional, and K0 value remained unchanged.Triaxial permeability tests showed that: there is remarkable anisotropy in the permeability of undisturbed soil sample of deep clay, the permeability coefficient kT in vertical direction under equal axial stress is less than permeability coefficient kH in horizontal direction, before sudden change (i.e. they have not reached the critical stress sections, respectively).The kH/kT ranges roughly between 1.1 and 1.3, the main reason lies in that: the flat clay particles settle directionally in vertical and horizontal direction in the environment of different stresses, resulting in tat the continuity of the pores in horizontal direction is generally better than that in vertical direction.The effect of horizontal earth pressure on the stability of well wall of the shaft under construction is calculated by the high Pressure K0 so as to simulate the actual conditions better, so has certain signification for guiding construction of the pit shaft.The paper have 48 maps, 34 tables, 195 references.更多还原