Research Of Directional Induced Fracture Grouting Mechanism In Tunnel And Its Supporting Test Methods

ABSTRACT:Fracture grouting is one of the most widely used method in grouting engineering, but its theory lags far behind its application. Especially in tunnel engineering, Fracture grouting is strongly influenced by the random of initial stress and cleavages. That makes the cleaving direction to extend to a wrong direction which is useless in reinforcing the stratum and preventing groundwater. A comparative Analysis whose conclusions can tell us the cleaving direction in tunneling fracture grouting engineering was done by numerical method and analytic method. So as to the disadvantage of conventional fracture grouting, a new style fracture grouting named directional induced fracture grouting was invented. It utilizes the installed induced hole to make the cleaving direction to extend to the right direction. A pilot numerical simulation of this method was done by RFPA2D.In different geological conditions, induced intervals between grouting hole and induced hole were calculated by this code mentioned above. In addition, to put this fracture grouting method into practice, the soil's mechanical parameters should be known first. However, the existing in situ tests which all most need to punch from ground surface to tunnel's face are time-consuming, energy-consuming and damage to the environment. Combining the features of tunnel engineering and fracture grouting, two new in situ test methods have been researched and designed. Whose name are "Test method of elastic parameter on rock and soil's surface" and "Test method of mechanical parameters in rock and soil's horizontal cavity" respectively. Those two methods are all based on precise theory and can acquire the majority of soils' parameters. So they can provide reference to the programming of directional induced fracture grouting. The former method is based on elastic theory, and can get the value of rock and soil's elastic modulus E. And whose calculating formula which was proved very precise was elaborated. Considering only one parameter can be got in this method, a new method, the latter one which can close cooperated with the fracture grouting engineering, was designed. At present, this method can get the value of rock and soil's still lateral pressure coefficient, Poisson's ratio, elastic modulus, cohesion and angle of internal friction.