盾构隧道施工引起的土体初始超孔隙水压力分布研究

Research on distribution of initial excess pore water pressure due to shield tunnelling

盾构施工会对周围土体产生扰动,形成超孔隙水压力,引起工后固结沉降。运用应力释放理论推导与衬砌相邻的土体初始超孔隙水压力计算公式。假定扰动范围边界呈圆弧状,确定初始超孔隙水压力的分布范围;同时运用应力传递理论,推导分布范围内任一点土体的初始超孔隙水压力计算公式。通过对实测资料的分析可知,计算值与实测值吻合较好。算例分析表明,与衬砌相邻的土体初始超孔隙水压力呈近似圆形(顶部小、底部大);随着到衬砌的径向距离增加,土体初始超孔隙水压力呈凹曲线形状;隧道底部的等值线最密,即变化最快;隧道顶部上方土体、不同深度处土体初始超孔隙水压力,以隧道轴线处为最大,呈现类似Peck曲线形状。

Excess pore water pressure is generated during shield tunnelling,resulting in consolidation settlement.Assuming the disturbance range shape of shield tunnelling is circular arc,the distribution range of excess pore water pressure is determined.The formula of initial excess pore water pressure of soil around tunnel lining is deduced by stress relief theory;and the formula of initial excess pore water pressure of soil within the region of its distribution at any point is subsequently deduced by stress transfer theory.By comparing calculated and measured data,it is shown that they are in good agreement.Based on practical example,a conclusion is drawn that the distribution shape of initial excess pore water pressure of soil around shield tunnel circle is roughly circular（top of small,bottom of large）.With the increase of distance from shield tunnel central axis,the initial excess pore water pressure of soil shows a concave curve shape.At the same time,the isopleths at the bottom of shield tunnel changes fastest.Above the top of the tunnel,the initial excess pore water pressure of soil gets the maximum at the tunnel axis in different depths,showing a similar Peck shape.