高压旋喷桩防渗墙钻孔注水和压水试验检测对比研究

为保证土石围堰的渗流稳定性和减少渗水量,需要在堰体内施工防渗墙。高压旋喷桩由于施工速度快、成本低而在围堰防渗结构中广泛应用。采用钻孔压水和钻孔注水试验对高压旋喷桩防渗性进行检测,分析钻孔压水、钻孔常水头注水和钻孔降水头注水试验检测高压旋喷桩防渗墙渗透系数的试验原理和计算方法。在现场检测中选取若干根整体性较好的高压旋喷桩,在同一钻孔取芯孔内分别进行压水、常水头注水和降水头注水试验。通过对3种试验方法的渗透系数结果对比分析发现,在桩体通长整体性较好的情况下,三者得到的渗透系数比较接近,分段压水试验得出的渗透系数比通长注水试验的结果稍大,但没有量级上的差异。在桩体某段存在缺陷漏水点的情况下,分段压水试验能够发现桩体漏水点,通长注水试验可能难以准确发现桩体漏水部位,当取芯发现桩体不均匀时要避免采用通长注水试验。

Comparative study on borehole of high-pressure jet grouting pile cutoff wall between water injection test and water pressure test

To ensure the seepage stability of earth-rock cofferdam and reduce water seepage,it is necessary to construct cutoff wall inside the cofferdam.High-pressure jet grouting pile is widely used in the cofferdam to reduce seepage because of its fast construction and low cost.Water injection test in borehole and water pressure test in borehole are used in the impermeability testing of high-pressure jet grouting piles.Firstly,the test principle and calculation method for the water injection test in borehole and water pressure test in borehole including constant head and precipitation head are analyzed,and then the high-pressure jet grouting piles with good quality are chosen to carry out the water pressure test in borehole and water injection test in borehole including constant head and precipitation head in the same coring borehole.The results show that the permeability values from three kinds of testing methods are close to each other when the quality of jet grouting pile is good,and the permeability coefficient of water pressure test in borehole is slightly larger than that of full-length water injection test in borehole without difference in magnitude.When there is a leakage point at certain part of the pile,the water pressure test in borehole can find the leakage point efficiently,while it may be difficult for the full-length water injection test to accurately find the leakage point,and the full-length water injection test should not be adopted if the pile is found inhomogeneous from coring.