超深MJS工法在岩溶发育区截水帷幕中的应用研究

Application of ultra deep MJS construction method in water-cutting-off curtain in karst development area

MJS工法引入国内后其适用范围不断扩大,加固深度从30m加大到60m左右。当周边环境敏感、深度较大时,可采用MJS工法施做截水帷幕。既有工程中未见MJS工法用于灰岩溶洞区截水帷幕的案例,文章以广州地铁某车站为例,详细介绍岩溶发育区57m深垂直MJS工法截水帷幕的设计、施工以及施工过程中异常情况的处理。研究应用实践表明:(1)提前处理溶土洞及裂隙是保证岩溶区MJS工法桩加固效果的必备措施;(2)MJS工法具备孔内强制排浆功能,其施工对围护结构变形、支撑轴力的影响均较小;(3)围护结构底部未嵌入稳固的岩层时,围护结构测斜数据应根据顶部水平位移监测值进行校核修正。相关研究成果可为岩溶发育区MJS截水帷幕的应用提供参考和借鉴。

After the introduction of MJS method into China,its scope of application has been expanded,and the reinforcement depth has been deepened from 30 m to about 60 m.When the surrounding environment is sensitive and the depth is large,the MJS method is a better choice to construct the water-cutting-off curtain.However,there have been no cases where the MJS method is used for water-cutting-off curtain in limestone karst cave area in existing projects.Taking a station of Guangzhou metro as an example,this paper introduces in detail the design and construction of the vertical MJS water-cutting-off curtain with a depth of 57 m in the karst development area,as well as the handling of abnormal conditions during the construction.Research and application practice show that:①Treatment of karst caves and fissures in advance is a necessary measure to ensure the reinforcement effect of MJS piles in karst areas;②MJS method has the function of forced slurry discharge in the hole,and its construction has little impact on the deformation of the enclosure structure and the supporting axial force;③If the bottom of the retaining structure is not embedded in a stable rock stratum,the inclinometer data of the retaining structure shall be checked and corrected according to the monitoring value of the top horizontal displacement.The research results may serve as reference for the application of MJS water-cutting-off curtain in karst development area.