具有随机几何缺陷的超高压旋喷桩止水效果研究

Study on the Water-stopping Effects of Ultra-high Pressure Jet Grouting Pile with Random Geometric Defects

由于设备精度、地层特性等因素影响,在旋喷、提升过程中,超高压旋喷桩不可避免地会出现直径缺陷和垂直度缺陷。为研究具有几何缺陷的超高压旋喷桩在暗挖地铁车站工程中的止水效果及适应性,以北京地铁3号线石佛营站3号施工竖井为例,研究几何缺陷对超高压旋喷桩止水效果的影响。基于旋喷桩成桩质量检测结果,归纳总结超高压旋喷桩的几何缺陷规律:旋喷桩直径服从平均值为1.1 m,标准差为0.11 m的正态分布,倾斜角度服从平均值为0.003°,标准差为0.3°的正态分布;倾斜方位角在[-180°,180°]内服从均匀分布。根据旋喷桩几何缺陷规律,建立三维缺陷计算模型,分析不同缺陷对旋喷桩止水效果的影响。研究结果表明:在旋喷直径和咬合厚度相同时,4种模型渗流量排序为双缺陷模型>直径缺陷模型>垂直度缺陷模型>无缺陷模型。基于数值模拟计算结果,提出超高压旋喷桩“临界咬合厚度”概念,为合理设置旋喷桩参数提供了依据。

Due to factors such as equipment accuracy and stratum characteristics,the diameter and perpendicularity defects of ultra-high pressure jet grouting piles will inevitably occur in the process of jet grouting and lifting.In order to study the water-stopping effect and adaptability of ultra-high pressure jet grouting piles with geometric defects in shallow buried excavation subway station engineering,the No.3 construction shaft of Shifoying Station of Beijing Metro Line 3 is taken as an example to study the effects of geometric defects on the water-stopping effect of ultra-high pressure jet grouting piles.Based on the test results of pile forming quality of rotary jet grouting pile,the geometric defects of the ultra-high pressure jet grouting piles constructed in Shaft No.3 are summarized:the diameter of jet grouting piles obeys the normal distribution with an average value of 1.1 m and a standard deviation of 0.11 m,and the inclination angle obeys an average value of 0.003°.The difference is a normal distribution of 0.3°;the tilt azimuth angle is uniformly distributed within [-180°,180°];a three-dimensional defect model is established based on the geometric defect law of the jet grouting pile,and the water-stopping effect of the jet grouting pile is analyzed.The research results show that when the jet grouting diameter and occlusal thickness are the same,the seepage flow of the four models is sorted as double defect model>diameter defect model>perpendicularity defect model>no defect model.Based on the numerical simulation results,the concept of "critical occlusion thickness" of ultra-high pressure jet grouting pile is put forward,which provides a basis for setting reasonable parameters of jet grouting pile.