一种处理桩基质量事故的方法-改桩为复合地基

Treating Method for Quality Accident of Piles—Reforming Original Unqualified Piles as Composite Foundation

某拟建在软土地基上的两栋60m×24m跨散装平房粮仓,基础采用振动沉管桩.由于桩基未能按设计要求进入持力层足够的深度,桩基承载力不能满足设计要求,因此,该库房地基基础必须进行处理.对桩基质量事故处理方案进行了详尽的技术经济比较,提出利用原已有桩改做刚性桩复合地基以承受上部荷载,论证了利用原桩基改做刚性桩复合地基在技术上的可行性.按刚性桩复合地基计算,复合地基承载力fk不小于100kPa,地基承载力满足要求;库房基础沉降约为80mm,在建筑物允许沉降范围内;库房内大面积堆载作用下桩身最大弯矩约为25kN·m,此值略低于桩的最大抵抗弯矩.单桩复合地基静载试验表明:复合地基承载力fk=140kPa.

Two bungalows were to be built, in which the span is 60 m ×24 m, and vibrator sunk pile with Φ377mm diameter is adopted to improve the soil-foundation. Because the depth of pile tip into bearing stratum could not satisfy design requirement, the actual values of the vertical ultimate carrying capacity of single pile could not satisfy design requirement. Therefore, the soil-foundation should be improved. Some treating method for quality accident of piles have been analyzed and compared carefully from the point of technique and economy, a modification scheme reforming original piles as rigid pile composite foundation is suggested. The calculation results show that the bearing capacity of composite foundation is more than 100 kPa, while the corresponding warehouse foundation settlement is about 80 mm,which satisfy the bearing capacity and allowable settlement of buildings, respectively. Moreover, the maximum moment of pile body under the load of loose grain in warehouse is 25 kN·m, and slightly smaller than that of pile resistance. All the above results illustrate that it is feasible to improve the warehouse soil-foundation by the suggested modification scheme.