异质岩块复合单裂隙岩体渗流试验及流固耦合机理分析

发布时间：2018-03-17 19:35

本文选题：裂隙岩体　切入点：渗透系数　出处：《山东科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：岩体是一种包含不同尺度节理裂隙的复杂天然地质体,由完整岩石和节理裂隙组成。在地铁隧道、海底隧道、煤矿巷道等地下工程中的岩体赋存于一定地质环境中,岩体的赋存环境主要包括地应力场及地下渗流场的作用,地下水在岩体裂隙里的流动过程中地应力场与渗流场之间会产生相互影响,这种相互作用是影响岩体渗透特性和工程稳定性的重要因素,因此研究岩体渗流过程中应力场与渗流场的耦合作用具有重要意义。裂隙岩体的流-固耦合研究多基于单裂隙的流-固耦合,从单裂隙研究入手研究多裂隙岩体流-固耦合是十分必要的。现有研究工作虽然在裂隙岩体渗流方面取得系列创新性成果,但对于不同性质地层接触区处裂隙面渗流特性的认识尚不全面,现有裂隙渗透理论还不能为实际工程中不同地层接触区处裂隙面渗透系数的计算提供可靠的理论依据和准确的计算方法。针对上述问题本文首先通过对人工制作的复合单裂隙细砂岩、复合单裂隙粗砂岩和复合单裂隙粗细砂岩岩体进行渗流试验,揭示裂隙面两侧岩性、裂隙水压及裂隙面法向应力对裂隙面渗透性的影响规律;然后基于三维应力下的裂隙-岩块位移模型,推导考虑裂隙面两侧岩性、裂隙面刚度系数、裂隙水压和裂隙面法向应力的裂隙岩体渗透系数理论计算公式;最后通过试验对新推出的裂隙岩体渗透系数计算公式的正确性及适用性进行了验证。通过研究本文得出以下主要结论:(1)在试验过程中,单裂隙岩体渗透系数随裂隙水压的增加呈线性增加,随着净围压的增加呈指数函数减小。(2)围压会引起裂隙的闭合,导致渗透系数减小;裂隙水压会使裂隙扩张,使裂隙渗透系数增加,并且在单裂隙扩展之初裂隙水压是影响裂隙初始宽度和初始渗透系数不可忽略的重要因素,因此在进行裂隙渗透系数理论计算时不宜仅用围压减去裂隙水压得到的净围压来进行计算,而应同时考虑裂隙水压对裂隙渗透系数的影响。(3)裂隙岩体裂隙面两侧岩块的岩性对裂隙渗透系数有显著影响,在相同的裂隙水压和围压共同作用下,单裂隙粗砂、单裂隙粗细砂岩复合体、单裂隙细砂的裂隙渗透系数各不相同,其中单裂隙粗砂岩渗透系数最大,单裂隙粗细砂岩复合岩体次之,单裂隙细砂最小。(4)本文基于裂隙岩体-位移模型,推导了考虑裂隙水压、围压与裂隙两侧为不同性质岩块的单裂隙岩体渗透系数计算模型及理论计算公式,并在试验中验证了其适用性和正确性,新推出的计算公式可为实际工程中不同地层接触区处裂隙面渗透系数的计算提供可靠的理论依据和相对准确的计算方法。
[Abstract]:Rock mass is a kind of complex natural geological body which contains joints and fractures of different scales. Rock mass in underground engineering such as subway tunnel, subsea tunnel, coal mine tunnel and so on occurs in a certain geological environment. The occurrence environment of rock mass mainly includes the action of ground stress field and underground seepage field, and the interaction between ground stress field and seepage field will occur during the flow process of groundwater in rock mass fissure. This interaction is an important factor affecting the permeability characteristics and engineering stability of rock mass. Therefore, it is of great significance to study the coupling of stress field and seepage field in the seepage process of rock mass. The fluid-solid coupling of fractured rock mass is mostly based on the fluid-solid coupling of single fracture. It is necessary to study the fluid-solid coupling of multi-fissure rock mass from the study of single fracture. Although the existing research work has made a series of innovative achievements in seepage of fractured rock mass, However, the understanding of seepage characteristics of fracture surface in the contact area of different strata is not comprehensive. The existing fracture permeability theory can not provide reliable theoretical basis and accurate calculation method for calculating the permeability coefficient of fracture surface in different strata contact area in actual engineering. Composite single fracture fine sandstone, In order to reveal the influence of lithology, water pressure and normal stress on the permeability of fracture surface, the seepage tests of composite single fissure coarse sandstone and composite single fissure coarse sandstone rock mass are carried out to reveal the influence of lithology, water pressure and normal stress on the permeability of fracture surface. Then, based on the three dimensional displacement model of fissure and rock mass, the theoretical formula of permeability coefficient of fractured rock mass considering the lithology, stiffness coefficient, water pressure and normal stress of fractured rock mass is derived. Finally, the correctness and applicability of the new formula for calculating permeability coefficient of fractured rock mass are verified by experiments. The permeability coefficient of single fractured rock mass increases linearly with the increase of fissure water pressure, and decreases with the increase of net confining pressure. The fracture permeability coefficient is increased, and the water pressure of the crack is an important factor which can not be ignored in the initial crack width and the initial permeability coefficient at the beginning of the expansion of a single fracture. Therefore, in the theoretical calculation of fracture permeability coefficient, the net confining pressure obtained by subtracting the water pressure of the fracture should not be used to calculate only the confining pressure. At the same time, the influence of water pressure on the permeability coefficient of fractures should be taken into account. (3) the lithology of rock blocks on both sides of fissure face of fractured rock mass has a significant effect on the permeability coefficient of fractures. Under the same water pressure and confining pressure, the coarse sand with single fissure should be taken into account. The permeability coefficient of single fissure coarse sandstone complex is different from that of single fissure fine sand, the permeability coefficient of single fissure coarse sandstone is the largest, and that of single fissure coarse sandstone composite rock is the second. In this paper, based on the fissured rock-displacement model, the calculation model and theoretical formula of permeability coefficient of single fractured rock mass are derived, which consider the water pressure of fissures, the confining pressure and the rock masses of different properties on both sides of the fissure. The new formula can provide reliable theoretical basis and relatively accurate calculation method for the calculation of permeability coefficient of fracture surface in different strata contact area in practical engineering.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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