基于弹性力学的诱导劈裂注浆机制分析

针对隧道内水平超前劈裂注浆中浆液劈裂方向随机性的问题，提出一种诱导劈裂注浆方法，可以控制和改变浆液的劈裂方向。首先，基于弹性力学理论及其基本假定，分析竖向地应力大于水平地应力条件下对单一土层进行劈裂注浆时浆液沿竖向劈裂的力学机制，在此基础上探讨改变浆液劈裂方向为水平劈裂的必要性和诱导方法，并从应力集中的角度分析诱导劈裂注浆的力学机制；其次，采用有限元法研究注浆孔孔周劈裂方向控制点的应力随侧向压力系数和诱导孔与注浆孔间距变化而变化的情况，得出实现诱导劈裂注浆时两孔间距及侧向压力系数应满足的条件，并拟合两孔间距临界值的计算公式。结果表明：在离注浆孔上、下方4倍注浆孔径以内对称布设诱导孔，改变了注浆孔孔周劈裂方向控制点的应力场。当两孔间距小于实现诱导的临界距离值时，注浆孔孔周控制点的应力大小发生转换，浆液的劈裂方向发生改变，将沿水平方向劈裂。诱导孔与注浆孔间距的临界值会随着侧向压力系数的增大而逐渐增大。

Mechanism analysis of induced fracture grouting based on elasticity

An induced fracture grouting method has been developed to solve the randomness of the splitting direction of fracture grouting in soil in tunnel. The objective of the method is to control and change the splitting direction of the soil. The results can be used to guide the design and construction of induced fracture grouting. Based on the elastic theory and its basic assumptions, the mechanism of fracture grouting in a single layered soil under the condition that the vertical in-situ stress is larger than horizontal in-situ stress is analyzed. And then the necessity of changing the splitting direction into horizontal as well as the induced method is discussed. The mechanism of induced fracture grouting is analyzed according to the stress concentration theory. By using the finite element method, a research about the stress distribution around the grouting hole is performed, in order to find out how it changes with the lateral pressure coefficient and distance between the grouting hole and the induced hole. The requirements about the lateral pressure coefficient and distance between the above two holes to achieve induced fracture grouting are studied. The formula for calculating critical value of distance between the above two holes is fitted. It is concluded that it appears possible to change the stress distribution around the grouting hole by excavating symmetrically the induced holes at its top and bottom positions; and the distance needs less than 4 times the diameter of the grouting hole. While the distance between the grouting hole and induced hole is less than the critical distance, the stresses of the control points around the grouting hole transform, as a result the slurry would split horizontally. In addition, the critical distance between the induced hole and grouting hole increases if the lateral pressure coefficient increases.