An experimental study of grouting in water-bearing ground based on the technology of gas driven water
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摘要: 当对含水地层进行灌浆改性时，通常会受到土体孔隙中自由水的不利影响。为此，考虑将以气驱水技术应用于含水地层化学灌浆中，以提高改性效果。对饱和黏土与粉质砂土开展以气驱水可行性试验，结果显示在饱和粉质砂土中充气驱替孔隙中自由水具有较好的可行性，在饱和黏土中则难以顺利进行。这是因为土体内部孔隙大小会直接影响初始进气值Pc，同时充气压力亦不能超过极限压力Pmax，否则土体内部会发生劈裂破坏，形成大范围空气通道；研制含水地层以气驱水化学灌浆模拟装置，以粉质砂土为研究对象进行对比试验，试验结果显示在以气驱水技术的辅助下进行化学灌浆可更加显著地改善原有土体的渗透性、无侧限抗压强度与微观结构，电子显微镜扫描也显示出相似结果，这是因为通过充气能够在含水地层中产生空气隔幕，为浆液提供良好的灌注、凝硬环境。Abstract: If the water-bearing ground is modified by grouting, the pore water will have an adverse influence on the grouting effect under normal conditions. In order to improve the grouting effect, the technology of gas driven water is proposed to apply to the chemical grouting in water-bearing ground. The feasibility test of gas driven water is carried out in the saturated clay and silty sand. The results show that the gas can drive the pore water in the saturated silty sand, but not in the saturated clay. The reason for this is that the size of soil pore will directly affect the initial air-entry value Pc. What’s more, the air pressure should not exceed the limit stress Pmax, otherwise the split failure and large-scale air passage will occur within the soil. An imitative experimental device for the gas driven water and chemical grouting in the water-bearing ground is designed, and some contrast test are conducted in the saturated silty sand. The results show that the chemical grouting can improve more significantly the permeability, unconfined compression strength and microstructure of the saturated silty sand with the aid of air charging technique, and the SEM photographs also show the same consequence. In general, an air curtain will be generated in the water-bearing ground via air charging, which can provide a favorable environment for the grouting, setting and hardening of grout.
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