强夯加固粉土地基的竖向附加动应力传递特性

Vertical additional dynamic stress transfer characteristics of silty foundation reinforced by dynamic compaction

强夯法在各类地基处理项目中得到了广泛应用,但其加固机理仍落后于实践,特别是强夯引起的地基内部竖向附加动应力传递特性。鉴于此,先基于Boussinesq应力解和动量定理推导强夯竖向附加动应力和附加剪应力拟静力解。然后,以新疆维吾尔自治区乌鲁木齐市机场北区扩建项目为工程背景,运用夯锤速度法,模拟1000~4000 kN·m能级间强夯引起的动力波传播过程、竖向附加动应力传递特性和夯后土体位移场。最后,将拟静力解与动力数值解的计算结果进行对比分析。研究结果表明:强夯引起的动力波传播呈半圆弧形,竖向附加动应力传递呈半椭圆形。动力波的传播距离决定了强夯影响范围,竖向附加动应力显著区边界决定了强夯有效加固区。由拟静力解得到的竖向附加动应力相比数值解沿深度方向的衰减更快。该研究结果可为强夯法地基处理工程提供重要参考。

Dynamic compaction method is widely used in various ground improvement projects,but its reinforcement mechanism still lags behind practice,especially the transfer characteristics of vertical additional dynamic stress induced by dynamic compaction.In view of this,the pseudo-static solution of vertical additional dynamic stress and additional shear stress of dynamic compaction are derived based on Boussinesq stress solution and momentum theory.Secondly,taking the north extension project of Urumqi Airport in Xinjiang as the engineering background,the hammer velocity method is used to simulate the dynamic wave propagation process,vertical additional dynamic stress transfer characteristics and soil displacement field induced by dynamic compaction between 1000~4000 kN·m energy levels.Finally,the calculation results of pseudo-static solution and dynamic numerical solution are compared and analyzed.The results illustrate that the dynamic wave propagation induced by dynamic compaction presents a semi-circular arc,while the vertical additional dynamic stress transmission presents a semi-elliptical shape.The propagation distance of dynamic wave determines the influence range of dynamic compaction,and the boundary of vertical additional dynamic stress determines the effective reinforcement region of dynamic compaction.The vertical additional dynamic stress calculated by the pseudo-static solution attenuates faster along the depth direction than the dynamic numerical solution.The research results can provide an important reference for the dynamic compaction ground improvement project.