高压旋喷锚索在超大软土深基坑中的应用

Application of High Pressure Jet Grouted Anchor in a Super Large Deep Excavation in Soft Soils

高压旋喷锚索支护技术具有造价低,工期短,方便土方开挖和主体施工等优点,相比传统注浆式锚杆,其锚固体的承载力显著提高,因此近年来在软土地区基坑工程中得以采用。位于苏州太湖边的某工程基坑是华东地区规模罕见的深大基坑,总面积达13.4万m^2,最大挖深达16.75m,该基坑地质条件复杂,综合技术和经济比选,采用了高压旋喷锚索支护技术。针对淤泥质土厚度大、土性软、灵敏度高的特点,采用锚杆角度调整,杆长交替变化以及锚索二次张拉锁定等一系列关键技术,有效地减小了杆体的松弛变形和应力损失,避免了群锚效应。结合施工工效考虑,在适当深度以下实施分块开挖,降低了超大深基坑的长边效应,监测结果显示变形满足周边保护要求。本基坑支护工程的实施,为软土地区基坑工程积累了成功经验,可供类似基坑工程参考。

In recent years,high pressure jet grouting anchor support technology receives more applications in the deep excavation engineering in soft soils.This method,comparing with the with the traditional grouting ground anchor,has the advantage of higher axial capacity due to the improved grouted portion.However,the application in super lager foundation excavation in soft soils with a supporting depth of more than 15 meters is still rarely reported.This paper presents a case history of applying this method in a very large deep excavation system near Taihu Lake,Suzhou City.The subsurface soil conditions at the project site have the characteristics of thick muck layer,highly compressible,and highly sensitive.During the jet grouted anchor installation,the inclination angle and length of the anchor were slightly adjusted and re-tension technique was used.The results were successful.