吹填区软土真空预压加固效果对比测试分析

为研究真空预压加固在温州沿海吹填区软土地基的适用性与加固效果,结合温州沿海某吹填区道路工程软土地基真空预压处理实例,通过室内土工试验和现场原位测试对加固前后吹填区软土物理与力学指标进行了对比分析。结果表明:真空预压能有效加固温州吹填区软土地基,预压加固后在地表15 m深度范围内土体物理力学指标有明显提高,但加固效果沿深度基本呈线性衰减; 加固后室内土工试验指标有一定改善,含水量和孔隙比降低约10%,压缩模量提高约10%; 同时现场原位测试指标提高更为明显,现场十字板剪切强度和静力触探侧阻平均增幅分别约为45%和40%,但加固前后土体灵敏度指标变化并不大,即真空预压加固对土体的灵敏度改善不明显; 采用传统真空预压法加固温州沿海吹填区软土地基在技术可行,经济上合理,其有效处理深度可达15 m; 受温州海相软土低渗透性和高黏性的影响,在竖向排水体周围出现明显的“土柱效应”,从而使真空预压加固效果在平面上呈现一定的不均匀性。

Comparative Test Analysis of Vacuum Preloading Reinforcement Effect on Soft Ground in Hydraulic Reclamation Area

In order to study the applicability and reinforcement effect of vacuum preloading on soft soil foundation in coastal hydraulic reclamation area of Wenzhou, combined with the example of vacuum preloading treatment of soft soil foundation of a road project in Wenzhou coastal hydraulic reclamation area, the physical and mechanical indexes of soft soil in hydraulic reclamation area before and after reinforcement were compared and analyzed through indoor geotechnical test and in-situ test. The results show that vacuum preloading can effectively strengthen the soft soil in Wenzhou hydraulic reclamation area, the physical and mechanical indexes of soil within 15 m of the surface were significantly improved after preloading reinforcement, but the reinforcement effect decreases linearly along the depth. After reinforcement, the indoor geotechnical test indexes are improved to some extent, the water content and void ratio are reduced by about 10%, and the compression modulus is increased by about 10%. The field in-situ test index is improved more obviously. The average increase of field vane shear strength and static lateral resistance are about 45% and 40% respectively. The sensitivity index of soil changes little before and after reinforcement, that is, the sensitivity of vacuum preloading reinforcement to soil is not significantly improved. It is technically feasible and economically reasonable to use the traditional vacuum preloading method to strengthen the soil foundation in Wenzhou coastal hydraulic reclamation area, and its effective treatment depth can reach 15 m. Meanwhile, there is an obvious “soil column effect” around the vertical drainage body affected by the low permeability and high viscosity of Wenzhou marine soft soil, so the reinforcement effect of vacuum preloading is uneven in the plane.