地下连续墙作为基坑围护结构起到支撑周围土层及防水的目的,接头处渗漏监测是检验嵌岩地下连续墙防渗质量的有效方法。结合南京地区采用"Ⅱ"型接头嵌岩地下连续墙的基坑实际工程,用20个监测孔对地下连续墙单元连接位置进行渗漏监测,结合接头处渗漏情况的现场监测数据,重点分析各监测孔的渗漏量大小、渗漏流速随深度的变化、渗透系数随深度的变化,并对"Ⅱ"型接头处做过与未做过高压旋喷钻孔灌注桩进行渗漏对比分析。监测结果表明:20个监测孔渗漏量均较小,其中按头部位做过高压旋喷钻孔灌桩处理的监测孔S4渗漏量最大,在深度8~25m范围内更易发生渗漏,该深度范围的渗漏流速及渗透系数也比其他深度的大,接头处做过高压旋喷钻孔灌注桩处理的监测孔S16~S20在深度35~55m范围也有上述现象;5个接头处未做过高压旋喷钻孔灌注桩处理的监测孔没有出现渗漏异常现象。
Diaphragm walls are often used as the retaining structure of the foundation pit to undertake the lateral earth pressure and to prevent the ground water from flowing into the foundation pit during excavation.Monitoring water leakage at position of diaphragm wall joints is an effective method to examine the leakage prevention quality of rock-socketed diaphragm walls.Combined with the specific foundation pit engineering of rock-socketed diaphragm walls with "Ⅱ"type joints in Nanjing,20 monitoring holes were set to monitor leakage at the connection position of diaphragm wall panels,and in-situ monitoring data of leakage condition at joint positions were used to focus on analysis of leakage volume of each monitoring hole,variation of leakage flow rate versus depth,and variation of permeability coefficient versus depth.And leakage conditions of two kinds of conditions were compared:one with high pressure jet grouting and bored cast-in-place pile around the"Ⅱ"type joints whereas the other without the pile.Monitoring results show that:the leakage volumes of 20 monitoring holes are all few,and the leakage amount monitoring hole S4 with high pressure jet grouting and bored cast-in-place pile around joints is the largest;leakage is more likely to happen at the depth from 8m to 25 m,and leakage flow rate and permeability coefficient at the depth from 8m to 25m are larger than that in other depth ranges.In addition,the same phenomena also can be seen in holes of S16~ S20 with high pressure jet grouting and bored cast-in-place pile around joints at the depth from 35m to 55m;there is no abnormal leakage phenomenon in joints without high pressure jet grouting and bored cast-in-place pile around.