注浆抬升地层的机制、解析解及数值模拟分析

Mechanisms of ground heave by grouting and analytical solutions & numerical modeling

注浆抬升地表是地下工程施工控制地层和邻近建筑物沉降的常用工法。目前,注浆设计主要依靠现场监测和工程经验。数值方法模拟注浆效果通常是通过提高注浆区域的土性参数来实现的,但该方法忽略了注浆抬升对地层的补偿作用。通过研究注浆引起的土体体积膨胀的机制,将注浆体积、土体体积应变增量、位移大小三者联系在一起。采用了一种模拟注浆抬升地层的数值方法。在该数值方法中,给出了土体体积应变的计算方法,提出了施加"虚拟"膨胀压力来增加单元体积,并通过判断单元体积应变增量是否达到土体体积应变增量来控制模拟注浆的过程。其方法的优点在于:施加在单元上的膨胀压力可以是一个虚拟的压力,而无需是实际注浆压力。通过解析解与数值解对比分析,验证了这种数值方法的正确性和可行性。

Grouting used to heave ground is a common measure adopted to control the settlements of ground and buildings in underground constructions.Presently,designs of grouting are based on field-monitoring and construction experiences.The numerical simulation of the grouting effect is realized by advancing the parameters of soil property in the grouting zone,while ignoring the compensation effect of ground heave due to grouting.The relationship of the volume of grouting,the soil volume strain increment,and the value of displacement is established by a study on the mechanisms of soil expansion caused by grouting.A numerical method is applied to simulate ground heave caused by grouting.In the numerical modeling,a method is defined to calculate soil volume strain.It is proposed to increase the volume of the element by applying a ＂fictitious＂ expanding pressure in the element.And The process of injection modeling can be controlled by estimating the element volume strain increment to see whether it has reached the soil volume strain increment.The advantage of this method is that the expanding pressure can be a ＂fictitious＂ stress in the element,but not a real one of grouting.Contrasting the numerical solutions with the analytical ones,the numerical method is proved to be proper and available.