深厚软基处理中袋装砂井长度的研究

Research on Length of Sand-wick Drain in Extra-deep Soft Soil Foundation Treatment

利用袋装砂井长度是砂井地基固结速率的重要影响因素,分析软基处理中处理区与下卧层之间的相互作用,对深厚软土地基固结度的计算方法进行合理改进,推导出计算固结度时砂井底面孔压不相连续的计算关系式,并从深厚软基中非理想因素、砂井长度方面对固结度的影响进行论述。结果表明,固结度随砂井长度的增加呈抛物线趋势先升后降。同时,从砂井长度对砂井处理费用的影响上进行定量关系计算,结果表明呈正相关性,因而,从理论上论证了袋装砂井最优长度的客观存在。通过某试验段工程实例,利用砂井深度与固结度增加百分比和投资效益比关系,结合总施工工期对固结度的要求、施工条件等对袋装砂井最优长度的确定方法进行研究,确定了最优砂井深度,实例计算结果表明,最优砂井深度为h0=22 m,利用沉降观测数据分析,比原设计的h=25 m砂井更为经济、合理,处理效果也达到设计要求。

The length of sand-wick drain is one of the crucial factors which influence the consolidation speed of sand well foundation.The computing method of consolidation degrees of the extra-deep soft soil foundation was improved. The uncontinuity of the pore water pressure on sand-wick drain bottom during calculating consolidation degree in traditional way was resolved considering the interaction between the treating area and subjacent bed. The influence of the non-ideal factor and the length of sand-wick drain on consolidation degree were investigated, especially on the deeper soft soil foundation.The results indicate that with the increase of sand well length, consolidation degree goes like parabola first up and then down. The positive correlation between the construction cost and the length of sand-wick drain was explored, which provided the theoretical basis to establish the optimal length of sand-wick drain. Based on the theory, the optimum sand well depth of one practical project was ascertained. Duringstudy, the relationship between the sand well length and the increasing percentage of consolidation degree, the relationship between the sand well length and the ratio of investment to output, the time limit for the project and the practical conditions were considered. The results show that the optimum length of sand-wick drain is 22 meters, which is more economical and effective than the designed value of 25 meters.