二元基坑新型吊脚墙(桩)技术工程实践

Engineering Application of New Suspended Diaphragm Wall(Pile)Technology of Soil and Rock Dualistic Foundation Pit

为给围护结构提供足够的末端嵌固,传统吊脚墙(桩)底部设置岩肩及预应力锁脚锚索。针对一种新型的无岩肩吊脚墙(桩)支护结构开展研究,依托实际工程,分别介绍了无岩肩吊脚桩、无岩肩长短吊脚桩、无岩肩吊脚墙的设计方案,并采用三维数值模型研究了3种支护形式的开挖变形特征,并与现场监测数据进行了比对,结果表明:该无岩肩无预应力锁脚锚索的新型吊脚墙(桩)支护形式,通过内支撑与吊脚结构,可保证支护段稳定;可视基岩的岩石强度、完整性灵活选择中风化、微风化岩层作为吊脚结构持力层,结合注浆、锚喷支护等措施并控制岩壁开挖质量,可保证岩壁段稳定;下部岩壁段开挖对上部支护结构的内力、变形及地面沉降影响甚微,均可忽略不计;数值模拟和现场实践均表明,3种支护方法均能保证基坑与岩壁段稳定。

In order to provide sufficient end embedment for the enclosure structure,rock shoulders and prestressed footing anchor cables are set at the bottom of the traditional suspended diaphragm wall(pile).A new type of supporting structure of non-rock shoulders suspended diaphragm wall(pile)is studied.Based on practical engineering,the design schemes of non-rock shoulder suspended pile,non-rock shoulder long and short suspended pile and non-rock shoulder suspended diaphragm wall are introduced,respectively.The excavation deformation characteristics of three supporting forms were studied by three-dimensional numerical model,and compared with the field monitoring data.The results show that the new supporting form of suspended diaphragm wall(pile)without rock shoulder and prestressed anchor cable can ensure the stability of supporting section through internal support and stilted structure.According to the rock strength and integrity of the visible bedrock,flexible choice of moderately weathered,slightly weathered rock as the footing structure bearing layer,and combined with grouting,anchor spray support and other measures to control the quality of rock wall excavation to ensure the stability of rock wall section.The excavation of the lower rock wall section has little effect on the internal force,deformation and land subsidence of the upper supporting structure,which can be ignored.Numerical simulation and field practice show that the three supporting methods can ensure the stability of the foundation pit and rock wall.