Study on Fracturing Phenonena of Soil Ground by Injection Materials

研究了化学灌浆、回填灌浆、泥浆加压、地面锚杆水泥浆加压等情况下地面的破裂现象，当注浆压力大于地面破裂压力时，即发生破裂。破裂压力取决于土体类型、围压、灌浆类型。研究了影响砂性土和粘性土破裂压力的一些因素。在试验中，明确了土的类型(渗透性、强度)、浆液粘度和围压对破裂压力的影响，并建立了破裂压力的计算公式。主要结论如下：1)压裂压力一般随注入材料粘度的增加而增大。然而，当注入材料的流量大于30s时，破裂压力趋于恒定。2)无论地基类型，流量大于30s的注入材料的破裂压力都可以达到空腔膨胀压力。3)具有隧道面形空腔的破裂压力略大于具有圆柱形空腔的破裂压力。4)当直径比(=试件直径/井眼直径)小于10时，破裂压力随着直径比的增加而增加。当比大于10时，压力变得恒定。

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.