水泥改良土融沉对地层位移场影响的数值分析

【目的】分析水泥改良土融沉对地层位移场的影响规律,为水泥土改良冻结法应用于城市地下工程提供理论基础。【方法】以南京地铁10号线盾构出洞水平冻结加固工程为研究对象,采用三维数值模拟方法对水泥改良土融沉引起的地层位移进行了分析,采用单因素分析法,分析了融沉系数、覆土厚度、冻土壁尺寸对融沉位移场的影响规律。【结果】冻结区土体未经水泥土改良时,地表最大融沉量为12.811 cm; 水泥掺入比为12%时,地表最大融沉量为1.521 cm,表明水泥的掺入可明显减小冻土融沉。【结论】水泥土融沉时,土层越深,融沉位移越大,融沉范围越小; 地表融沉位移呈盆状沉降面,最大沉降位于出洞口处,随融沉系数增加,地表最大融沉量逐渐增大,但地层沉降分布规律不变; 覆土厚度越大,地表融沉量越小; 冻土壁尺寸增加时,地表位移发展速度变缓,地表沉降时间延长,最终融沉量增大。

Numerical analysis of the influence of cemented soil thawing settlement on the stratum displacement field

【Objective】 Research on the influence of cemented soil thawing settlement on the stratum displacement field can provide a theoretical basis for the application of cemented soil freezing methods in urban underground engineering. 【Method】Taking the shield tunneling horizontal freezing reinforcement project in Nanjing metro line 10 as an example, a 3-D numerical simulation analysis is conducted on the stratum displacement field caused by the cemented soil thawing settlement. The effect of the thaw settlement coefficient, thickness of the covering soil, and size of the frozen soil wall on the cemented soil displacement field are studied using the single factor analysis. It was found from research that the amount of maximum surface thawing settlement is 12.811 cm as the frozen soil had not improved; when the cement-mixed ratio is increased to 12%, the maximum surface thawing settlement amount reduces to 1.521 cm, revealing that mixing of cement can significantly decrease the thawing settlement of the frozen soil. 【Conclusion】 In the freezing thawing settlement of the cement soil, the deeper the soil is, the larger the thawing settlement displacement is and the smaller the thawing settlement range is. The surface thaw displacement shows a basin shaped settlement, with the maximum settlement displacement located at the outlet. With the increase in the thawing settlement coefficient, the amount of maximum surface settlement increases gradually, but the soil displacement distribution does not change; the larger the covering soil thickness, the smaller is the surface settlement. When the frozen wall size is increased, the rate of development of surface displacement decreases; thus, the surface settlement time increases, and finally the thaw displacement increases.