开采地下水条件下地裂缝形成机理及数值模拟研究

Excessive groundwater withdrawal can result in earth fissures and cause huge economic loss. However, many problems regarding earth fissures, especially the mechanism and numerical simulation, have not been satisfactorily solved yet in the world. Based on extensive geological survey and deep analysis of field data of groundwater level, compaction of individual soil layers, land subsidence, and earth fissures for a typical earth fissuring area, this project will study the tensile and shear failure of soils under different changing patterns of groundwater level and study the mechanism of earth fissuring from the viewpoint of soil failure. In this project, an earth fissure will be represented by a smeared blunt crack band, which is proposed on the basis of fracture mechanics. Thus earth fissures can be simulated numerically through the finite element method without remeshing when they initiate and propagate. The numerical model for earth fissuring proposed in this project will be examined and calibrated by the field data of the study area, and then the examined and calibrated numerical model will be used to predict the initiation and propagation of earth fissures due to groundwater extraction. The outcomes of this project can be used as the instructions for reasonably exploiting groundwater and preventing ground surface from fissuring. The ideas and methods used in this project are creative and novel. The research achievements of this project has great scientific meanings for the further development of soil strength, mechanism and numerical simulation of earth fissuring, and has important practical values for the predition and prevention of earth fissures and for the plan of groundwater withdrawal.

过量开采地下水会导致地面开裂，造成巨大的经济损失，但目前国内外在地裂缝研究方面还有很多科学问题未得到很好解决，特别是地裂缝的形成机理和数值模拟方法。本项目将在对典型地裂缝地区进行广泛地质调查和对地下水位、土层变形、地面沉降、地裂缝等监测资料深入分析的基础上，通过试验研究土体在不同地下水位变化模式下的拉伸和剪切破坏特征，采用基于断裂力学的钝断裂带模型来表征地裂缝，建立刻画地裂缝形成和发展过程的数值模拟方法，揭示地裂缝形成机理。利用研究区实际观测资料，对所建立的数值模型进行识别和检验，并将经识别和检验的模型应用于地裂缝的预测预报，为合理规划地下水开采、防治地裂缝灾害提供科学依据。本项目研究地裂缝的思路和方法独特，创新显著,其研究成果对土体强度理论、地裂缝的形成机理、地裂缝数值模拟的进一步发展具有重要的科学意义，对地裂缝的科学预测和合理防治以及地下水开采的合理规划具有重要的实际应用价值。

过量开采地下水不仅会引起地面沉降，也可能引起地面开裂，地裂缝往往伴随着地面沉降而发生。地裂缝极大地威胁着地表及地下建（构）筑物的安全和正常使用，也给地表水体提供了直接渗入地下含水层的通道，造成农田灌溉水渗漏及地下水体污染，同时地裂缝的出现也会给当地社会造成一定的恐慌，使大面积土地资源遭弃置，造成巨大的经济损失。由于问题的复杂性，目前国内外在地裂缝研究方面还有很多科学问题未得到很好解决，特别是地裂缝的形成机理和数值模拟方法。本项目在已有研究基础上，以典型采水型地裂缝地区（江苏苏锡常地区）作为研究区域，研究地裂缝的时空演变特征，研究在地下水开采引起的缓慢、反复的有效应力作用下土体拉裂破坏和剪切破坏特征以及地裂缝形成机理，研究基于断裂力学、能够刻画地裂缝形成和发展过程的数值模拟方法。本项目解决了地裂缝研究和防治中长期存在的难题，深化了地裂缝的形成和演变机理，有效模拟了地裂缝的发生位置和演变过程，为地裂缝灾害防治和工程建设规划提供了切实可行的模拟方法。项目研究成果对土体强度理论、 地裂缝形成机理、地裂缝数值模拟的进一步发展具有重要的科学意义。