初始固结度影响下地铁运营引起的长期沉降预测

Prediction of Long-Term Settlement Caused by Subway Operation under the Influence of Initial Consolidation

地铁运营引起的长期沉降包括不排水累积残余变形引起的沉降和循环孔压消散引起的固结沉降。前者基于累积塑性变形经验公式,通过地基土应力三维有限元计算模型,采用分层总和法计算求得;后者采用室内动三轴试验模拟不同固结度下孔压变化规律,通过对试验数据的拟合得到了不同固结度下杭州软土受循环荷载作用的孔压计算模型,结合太沙基一维固结理论计算固结沉降,进而得出了地铁列车循环荷载作用下的长期沉降。结果表明,残余变形引起的沉降在加载初期发展较快;循环孔压消散引起的沉降约为总沉降的30%,该比例随着固结度的提高而降低,并且此部分沉降在半年后将趋于稳定。

Long-term settlement caused by subway operation can be divided into settlement caused by undrainedaccumulated residual deformation and consolidation settlement caused by cyclic pore pressure dissipation, the for-mer of which is obtained by the layer-wise summation method based on the empirical formula of accumulated plas-tic deformation and a three-dimensional finite-element model of the foundation soil stress, and the latter of which isobtained by a dynamic triaxial test that simulates pore pressure change rules under different initial consolidation de-grees. Through fitting of experimental data, a pore pressure calculation model is established for the Hangzhou softsoil under different consolidation degrees and cyclic loading, and combined with the consolidation settlement calcu-lated by one-dimensional Terzaghi consolidation theory, long-term settlement under cyclic subway traffic loadingcan be obtained. The results show that settlement caused by residual deformation develops rapidly at the early load-ing stage, settlement caused by pore pressure dissipation occupies about 30% of the total settlement, and this ratiodecreases with the increase of the consolidation degree and tends to be stable after six months.