【作者】 蒋臻蔚；

【导师】 彭建兵；

【作者基本信息】 长安大学 ， 地质工程， 2011， 博士

【摘要】 水是地裂缝形成及加剧发展的重要因素,这是大家所公认的,但是关于其具体的作用机制问题,一直以来却争议颇多。究其原因,一方面是水土相互作用的机理很复杂,二是各个地区地质环境条件各异。开展水作用下的地裂缝综合成因机制的研究,具有重要的科学意义和社会价值。本文所作的主要工作,一是对水土相互作用的类型及模式进行了分析,总结了水作用下土体物质流动、物理力学性质和地质环境场变化的成因机制；二是分别采用理论分析、数值模拟等方法对水作用下地裂缝的成因机理进行了研究；三是结合西安地裂缝、三原双槐树村地裂缝的实例分析,验证了理论模型的正确性,并对一些传统的认识进行了科学的解释。主要的工作及创新性成果如下：(1)基于随机介质理论对抽水沉降致裂机理进行了研究,结果表明由于抽水作用将在沉降中心区形成挤压区、在沉降边缘区形成张拉区,张拉区的应变在地面沉降漏斗的曲率变化最大处达到最大值,从而引起自上而下发展的张性地裂缝。(2)采用考虑偶应力的Mohr-Coulomb理论对抽水致裂机理进行了分析,结果表明抽水作用下产生的差异沉降,将会在土体单元中产生附加偶应力的作用,该作用使得单元应力呈现非对称的特点,从而使得强度曲线中的摩尔圆偏转,加大了土体剪切破坏的可能,从而在土体中形成剪切地裂缝。(3)首次采用基于弱面破坏和塑性滑动的理论对地裂缝活动进行了研究,结果表明具有先期断裂存在的地裂缝在抽水等扰动力的作用下,由于弱面抵抗变形和破坏的能力差,断裂容易再次破坏并沿破裂面发生滑移,该效应是西安这类具有先期隐伏断裂的地裂缝形成及发展的最主要因素。(4)通过建立考虑水土耦合作用并考虑先期断裂的数值计算模型,作者模拟计算了单裂隙抽水作用下的发展过程,并对其影响因素进行了敏感性分析计算,结果表明先期断裂对地面沉降具有诱导,隔离和放大的作用；地裂缝的强度参数内摩擦角和几何参数倾角对地裂缝活动的敏感性强。(5)通过对西安祭台村地裂缝段水文、地质、地貌等条件的分析,建立了考虑两条地裂缝的精细计算模型,计算结果与实际吻合较好。模型计算验证了很多问题,并取得了一些新认识：①西安地裂缝与抽水作用直接相关,但其活动的主要因素是下伏断层控制作用下的弱面破坏和滑移效应,抽水沉降漏斗和地层差异导致的差异沉降只是次要的因素；②西安的梁洼地貌对地裂缝的发展有一定的影响,梁洼相对高差大的先期发展要快一些,但总的量值相差不大。(6)浅表水作用下地裂缝的形成机制包括黄土湿陷致裂机制、冲蚀溶蚀致裂机制、水压致裂机制、失水收缩开裂机制等,三原双槐树村地裂缝暴雨开裂的分析表明,该地裂缝是在隐伏地裂缝的优势控水作用(包括阻水、截水作用,导水与强渗水作用)下,暴雨时引起的劈裂效应,冲刷效应和拖曳牵引效应的综合作用而造成的。更多还原

【Abstract】 It is accepted that water is the most important factor to the formation and development of the ground fissures. But the specific mechanism is a controversial question. The reasons are the complex mechanism of water-soil action and different geological environmental conditions. It has important scientific significance and social value to carry out the research on the comprehensive formation mechanism of the ground fissures by the action of water.In this paper, the main works done are as follows. Firstly, the types and modes of water-soil action are studied. Formation mechanism of the flow of soil material and the changes of physico-mechanical properties and geological environment are summaried. Secondly, formation mechanism of the ground fissures under the role of water is researched by theoretical analysis and numerical simulation. Thirdly, through analysizing the ground fissures in xi’an city and shuanghuaishu village of sanyuan, the validity of theoretical mode is verified. And some traditional understandings are explained scientificly.The main work and innovative results are as follows:(1) Based on the theory of random medium, the ground fissures caused by extractive are studied. The results show that the crush zone would be formed in settlement central area and the tension zone would be formed in settlement fringe area owing to extractive function. The strain of tension area in the biggest curvature change of the subsidence funnel reaches the maximum value, so the tension-cracks are developed from top to bottom.(2) Based on the theory of Mohr-Coulmb considering the accidentally stress, the ground fissures caused by extractive are studied. The results show that different subsidence produced under the action of extractive would generate additional couple stress role in the soil mass unit. The role makes the unit stress present the asymmetric feature and causes the Mohr-round to deflect. The possibility of soil shear failure is increased and the shear-cracks are developed.(3) Based on the theory of damage of weak surface and plastic sliding, activities of the ground fissures are researched firstly. The results show that the ground fissures developed on the basis of early fractures are very easy to damage again and to slide along the fracture surface under the action of extractive and other disturbing forces, because the ability of weak surface to resistant deformation and failure is poor. The effect is the main factor to the formation and development of the ground fissures developed on the basis of early fractures in xi’an city.(4) Through the establishment of numerical calculation model considering water-soil coupling and the prior fracture, the author simulates the development of single fissure under the action of extractive and analyzes the sensitivity of influence factors. The results show that the prior fracture has effect of induction, isolation and enlargement. And the parameters of ground fissures, such as internal friction angle and dip angle, are sensitive strongly to the activities of the ground fissures.(5) Through the analysis of hydrology, geology, geomorphic conditions of the ground fissure in jitai village of xi’an city, the author establishes a fine calculation model including two ground fissures.The calculation results are in good agreement with the actual. Model calculation verifies many problems and some new understandings are achieved:①The activities of ground fissures in xi’an city are relate to extractive directly. But the main activities are the damagement of weak surface and slippage effect under the control of subjacent faults. Descend funnel by extractive and different subsidence caused by stratigraphic differences are just the minor factors.②Ridge-depression physiognomy in xi’an has certain effection to the development of ground fissures. The big relative elevation of ridge-depression physiognomy develops quickerly in advance, but they have little difference in the total magnitudes.(6) The formation mechanism of ground fissures by the action of superficial water includes failure mechanism caused by collapse of loess, failure mechanism caused by erosion and corrosion, failure mechanism caused by hydraulic pressure, failure mechanism caused by water loss shrinkage, and so on. Through analysizing the ground fissures in shuanghuaishu village of sanyuan caused by rainstorm, the results show that the ground fissures caused by the comprehensive function of fracturing effect, scouring effect, drag traction effect during rainstorm under preponderant controlling role of concealed ground fissures, incuding water-blocking and water-interception role, permeability and strong seepage role.更多还原