Study on Fracturing Phenonena of Soil Ground by Injection Materials

本课题研究了化学灌浆、回填灌浆、浆式盾构施工中浆体加压、地锚中水泥乳加压等情况下的地面破裂现象。当注入压力大于地面压裂压力时，发生压裂。而破裂压力取决于土壤类型、围压和注浆类型。对影响砂质土和粘性土破裂压力的因素进行了研究。在试验中，明确了土体类型（渗透性、强度）、浆液黏度、围压的影响，并建立了压裂压力的计算公式。主要结论总结如下。1)压裂压力一般随着注入材料粘度的增大而增大。而当注入物流量值超过30秒时，压裂压力趋于恒定。2)注入物流量值大于30秒左右时，无论何种地面，注入物的压裂压力均可达到空腔膨胀压力。3)巷道端面空腔的破裂压力略大于圆柱空腔的破裂压力。4)当直径比（=试件直径/钻孔直径）小于10左右时，压裂压力随直径比的增大而增大。当比值大于10时，压强保持不变。

This research project deals with the fracturing phenomena of ground in the cases of chemical grouting, backfill grouting, pressurization of slurry in slurry type shield tunneling, pressurization of cement milk in ground anchor and so on.When the injection pressure is larger than the fracturing pressure of ground, the fracturing occurs. And the fracturing pressure depends upon the soil type, confining pressure, types of grouts. The author studies some factors related to the fracturing pressure of sandy and cohesive soils. In experiments, the effects of soil type (permeability, and strength), viscosity of grouts, and confining pressure were clarified and the equation which gives the fracturing pressure was supposed. Main conclusions were summarized as follows.1) The fracturing pressure generally increases as the viscosity of injection materials increase. However, the fracturing pressure become constant when the flow value of injection material exceed 30 sec.2) The fracturing pressure with injection materials which flow value is larger than about 30 sec can be reach to the cavity expansion pressure, irrespective of types of ground.3) The fracturing pressure which have a tunnel-face-shaped cavity is a little larger than that have a cylinder-shaped cavity.4) The fracturing pressure increases as the diameter ratio (=diameter of specimen/diameter of borehole) increases when the ratio is less than about ten. And the pressure become constant when the ratio is larger than ten.