软土地区桩基施工中的孔隙水压力监测标准探讨

Discussion on monitoring criterion of excess pore water pressure induced by driving piles in soft soil area

软土地区桩基施工产生的挤土效应会严重影响成桩质量,孔隙水压力监测作为一种重要的监测手段对于信息化指导桩基施工意义重大,但目前的孔压监测标准由于未全面地考虑土性的影响,尤其是饱和软粘土中结合水的性质和土体自身强度,故在工程实践中的应用效果不甚理想。本文将强结合水视作土体骨架的一部分,对软土中上覆有效应力的计算模式进行了修正,提出了以单桩沉桩引起桩周土超孔隙水压力理论公式为基础的孔压监测标准,较好地反映了控制沉桩速率和调整打桩区域对孔压变化规律的影响。

The extruding effect in driving piles influences the quality of the completed piles in soft soil area. The monitoring of excess pore water pressure,as an important monitoring method,is very meaningful to guide the information construction of piles. Owing to the incomplete consideration on the characteristics of bound water and soil strength,the current monitoring criterion of excess pore water pressure is not applied well in engineering practices. In the paper,the strongly-combined water is assumed as a part of soil skeleton,by which the calculation method for effective overburden pressure in saturated soft clay is modified,and the monitoring criterion of excess pore water pressure based on theoretic equation for excess pore water pressure of soil induced by the single pile driving is established. This criterion preferably reflects the effects of controlling speed and changing area in driving piles on the variation of excess pore water pressure.