基于各向异性本构的软土路基沉降机制与加固分析

Settlement Mechanism and Reinforcement Analysis of Soft Soil Subgrades Based on Anisotropic Constitutive Model

摘要:

以万环西路南延线深厚软土路基工程为背景，通过UMAT子程序二次开发将K₀-MCC模型嵌入有限元软件ABAQUS，建立了考虑土体各向异性的深厚软土路基有限元计算模型，对路基填筑产生的沉降量、孔隙水压力和水平位移进行了计算，通过与现场实测数据对比验证了建立模型的正确性，剖析了深厚软土路基沉降变形机制，进一步通过对比分析水泥搅拌桩和预应力管桩加固控制沉降效果，提出适合深厚软基的加固方法。研究结果表明：土体初始应力各向异性特性及应力诱发各向异性对软土路基的沉降变形具有明显影响；深厚软土路基两次堆载过程中产生的沉降为0.337 m，而首次堆载结束后施工间歇期内产生的固结沉降仅为0.005 m，堆载结束后1年内随超孔隙水压力消散以及持续路基荷载作用下沉降继续发展，总沉降量达到0.366 m，路基堆载施工过程中产生的沉降占总沉降的92 %；路基填筑施工后，深度越浅且越靠近路基中心处沉降变形越大；预应力管桩加固技术相对于水泥搅拌桩在深厚软土路基施工沉降控制方面更具优势，尤其在控制总沉降量及长期沉降方面表现突出。

Abstract:

Taking the deep soft soil subgrade project of the South Extension of Wanhuan West Road as the background， the K₀-MCC model was embedded into the finite element software ABAQUS through secondary development of a UMAT subroutine to establish a finite element model of deep soft soil subgrades considering soil anisotropy. Settlements， pore water pressures， and horizontal displacements caused by subgrade filling were calculated. The model’s validity was verified by comparison with field-measured data. The settlement and deformation mechanisms of deep soft soil subgrades were analyzed. Furthermore， by comparing the effectiveness of cement-mixed piles and prestressed pipe piles in controlling settlement， reinforcement methods suitable for deep soft subgrades were proposed. The results indicate that the initial stress anisotropy of the soil and stress-induced anisotropy have significant effects on the settlement and deformation of soft soil subgrades. The settlement during the two-stage surcharge of the deep soft soil subgrade reached 0.337 m， while the consolidation settlement occurring during the construction interval after the first surcharge was only 0.005 m. Within one year after the surcharge， as excess pore water pressure dissipated and the subgrade continued to bear load， settlement further developed， reaching a total of 0.366 m， with settlement generated during surcharge construction accounting for 92 % of the total. After subgrade filling， settlements were larger at shallower depths and closer to the subgrade center. Compared with cement-mixed piles， prestressed pipe pile reinforcement is more effective in controlling construction settlement of deep soft soil subgrades， particularly in terms of total and long-term settlement control.