饱和黏土中搅拌桩施工引起的超孔隙水压力计算

EXCESS PORE PRESSURE AROUND DEEP MIXING COLUMNS IN SATURATED CLAY

水泥土搅拌桩在地基处理过程中产生一定的挤土效应,靠近桩身的土体发生屈服并产生很高的超静孔隙水压力。为得出饱和黏土中搅拌桩施工引起桩周超孔压问题的精确解答,文中采用钻杆和注浆对土体置换的方式确定扩孔半径,通过联合平衡方程、不排水强度的屈服准则并充分考虑不排水强度与有效上覆土压力的关系,推导了桩周超孔隙水压力沿半径和竖直方向分布的解析解。此外,基于桩施工引起的劈裂行为,推导了在竖向劈裂控制条件下的超孔压分布近似解。理论计算与现场实测值对比表明,两种计算方法均可以较好地反映搅拌桩施工引起的超孔隙水压力,因而可以广泛地应用于搅拌桩地基处理引起的超孔隙水压力和土压力的定量分析。

The construction of the deep mixing pile has a large disturbance effect on the surrounding soil.The soil near the pile yields and generates a high excess pore water pressure.In order to obtain an accurate solution to the problem of excessive pore pressure around piles caused by mixing piles in saturated clay,the drill rod and grouting are used to replace the soil body to determine the radius of the cavity expansion.By combining the equilibrium equation,the yield criterion of undrained strength,and fully considering the relationship between undrained strength and over burden effective pressure,an analytical solution for the distribution of excess pore water pressure along the radius and vertical direction around the pile is derived.Additionally,an approximate solution of the excess pressure distribution under the condition of vertical splitting is derived based on the soil splitting behavior caused by pile construction.The comparison with the measured values on site shows that both calculation methods can better reflect the excess pore pressure caused by the construction of mixing piles.