软土地基刚性桩复合地基沉降计算的简化方法
Simplified method for settlement calculation of rigid pile composite foundation in soft soils
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摘要: 既简便又具有较好精度的刚性桩复合地基沉降计算方法仍是工程实践中迫切需要而又有待于解决的问题。对于软土地基中的刚性桩复合地基沉降计算,现行规范方法把其沉降分为加固区的沉降和下卧层的沉降,加固区复合模量的提高采用复合地基与天然地基承载力的倍数求得,实际发现这样得到的加固区复合模量的提高不够,造成计算沉降偏大。本文认为造成这种情况的原因是由于公式推导中假设了桩土应力比与桩土承载力比相等而造成的。另外对于软土地基刚性桩复合地基沉降计算,当桩底置于可靠持力层时,提出其复合地基的沉降可以简化为桩的沉降加褥垫层的压缩沉降的简化方法。工程实例表明,简化方法既简便又具有较好的精度,可为工程实践提供一个有效实用的计算方法。Abstract: To find a simple and precise settlement calculation method for rigid pile composite foundation is still an urgent problem which is not solved as yet. For the settlement calculation of rigid pile composite foundation in soft soils by using the existing standard method, the total settlement can be the sum of reinforced area and substratum, the improvement of composite modulus in the reinforced area can be obtained by the bearing capacity ratio of compound foundation to natural foundation. In fact, the calculated results of settlement are usually too large because the inadequate improvement of composite modulus by using the above method. It is put forward that the reasons for this situation are the unreasonable hypothesis in formula derivation that the pile-soil stress ratio is equal to the pile-soil bearing capacity one. For the settlement calculation of rigid pile composite foundation in soft soils, a simplified method is proposed that the settlement of reinforced area can be the sum of pile settlement and cushion compress settlement when the pile tip is placed at reliable bearing stratum. The calculation of engineering examples shows that the simplified method is simple and precise, and it can provide an effective and practical calculation method for engineering practice.