考虑桩端土体加固效果的挤密砂石桩间距计算方法

A METHOD TO CALCULATE SAND-STONE COMPACTION PILE SPACING CONSIDERING REINFORCEMENT EFFECTS OF SOIL AT PILE TIP

若干砂性土地基上采用振动挤密砂石桩处理的工程实测资料表明,沉桩施工对桩端以下一定深度土体的加固效果也相当明显。考虑此影响,提出桩端加固影响深度的概念,并基于土颗粒体积在地基处理前后保持不变的前提对振动挤密砂石桩桩间距的理论计算公式进行推导。在已有研究的基础上,进一步提出同时考虑细颗粒含量影响,并用标准贯入击数表达的桩间距实用计算式,通过在实际工程的应用及与现有计算方法的比较,验证该计算方法的合理性。

In order to put forward a theoretical formula to calculate the spacing of the sand-stone compaction piles on sandy ground,some previous engineering practices and field tests on the composite foundation with sand-stone compaction piles are studied.As the reinforcement effects of soil at the pile tip and around the pile shaft are noticed.A new concept,reinforcement depth at the pile tip,is put forward.Based on the constant volume of soil grain before and after the foundation reinforcement,a new method is theoretically investigated to estimate the piles spacing taking both the lateral and vertical compaction and vibration effects at the pile tip into account.The method correlated the calculation of pile spacing with standard penetration test(SPT) blow counts as well as the fine-grained content to facilitate its use in engineering practice and design.By comparing the results of a case gained by previous and present methods respectively,the reasonability of the method is testified.