海相沉积软土地区人工冻土强度特性试验研究

Experimental study on mechanical properties of artificial frozen soil in marine sedimentary soft clay

人工冻土的物理力学指标是地铁隧道工程冻结壁设计参数和开挖的依据。通过对宁波轨道交通一号线联络通道②～⑤海相沉积软土地层人工冻土的室内单轴抗压强度和抗剪强度试验,获得了冻结前后②～⑤土层的比热容、导热系数、内摩擦角和粘聚力的对比结果以及不同温度条件下冻土的极限抗压强度、弹性模量和泊松比结果。试验结果表明:②～⑤土层人工冻结土的物理力学指标较原状土有很大的提高,人工冻土极限抗压强度、弹性模量随温度的降低而增大,近似呈线性关系。各土层泊松比、温度的变化对冻土泊松比影响较小,随温度的降低有一定的减小。在-10℃条件下,冻结前淤泥质土、粘土层的内摩擦角和粘聚力有了大幅的提高,而③1砂土层的内摩擦角增幅较小。

In the ground freezing,the mechanical properties of the soft clay have a remarkable change after it is frozen.The mechanical parameters of frozen soil in urban rail transit project are the basis of freezing wall design and tunnel excavation.In this paper,the uniaxial compressive strength and shear strength test of frozen soil of the ② ～ ⑤ layer marine sedimentary soft clay for the passway of tunnels in the line 1,Ningbo urban rail transit project are executed.The specific heat capacity,thermal conductivity,internal friction angle and cohesion for the undisturbed soil and frozen soil,and the ultimate compressive strength,elastic modulus and Poisson ratio in different temperature for the frozen soil are obtained.The test results show that the mechanical parameters of ② ～ ⑤ stratums are improved greatly after freezing due to the high water content.The uniaxial compressive strength and shear modulus linearly increase with the decrease temperature,but there is a little influence of decrease temperature on the decrease of Poisson ratio.The internal friction angle and cohesion at-10℃ increase remarkably in comparison with the undisturbed soil in the soft clay,and the increase of internal friction angle in ③1 sand layer is small.