抗拔桩在人防地下室工程中的应用

Application of uplift-piles in civil air defence basement

银川市某单建式人防地下室工程,埋深较深,处于砂类土地基高水位环境,结构自重不足以克服地下水产生的上浮力.经过方案比选和经济分析,最后采用钢筋混凝土灌注桩作为抗拔桩解决了抗浮问题.通过工程实录,着重介绍了抗拔桩的受力机理、设计及承载力计算.抗拔桩的计算方法采用了文献[1]推荐的经验公式,即以试桩实测资料为基础建立桩的抗拔阻力与抗压阻力之间的关系,引入一个经验折减系数,即抗拔系数λ值.以桩的抗压侧阻力乘以λ值后,用作抗拔侧阻力来估算抗拔承载力.采用泥浆护壁钻孔灌注桩,水下浇筑混凝土施工工艺.用动测法检测桩的完整性和抗压承载力.工程建成后通过验收并投入使用多年,经现场观察未发现上移现象,证明桩是稳定可靠的,达到了设计要求,并取得了一定的经济效益和社会效益。

A single civil air defence basement engineering in Yinchuan, which located on high waterlevel sandy foundation with deeper buried depth, its dead-weight is not enough to prevent the buoyancy of groundwater. By means of the plan comparison and economic analysis, steel-concrete cast-in-place was used for uplift pile to solve this problem. In this paper, the load-carrying mechanics and design calculation of uplift pile are introduced. The calculation method of uplift pile applied the empirical formular introduced in reference [1], which used the experimental data to settle the relation between uplift resistance and compression resistance, quoted a empirical factor λ, multiplied compression resistance by λ, using for uplift resistance to estimate uplift bearing capacity. Craft is adopted hole wall mud protection poring piles and concrete pouring underwater method. Dynamic measurement method is adopted to detect the integrality and compression bearing capacity of pile. Through engineering acceptance and using for many years, there has no up-displacement, which means the uplift pile is steady and reach the design requirement, get a considerable of economic and social property.