基于新型人工软土技术的加筋碎石桩复合地基承载特性模型试验

为研究地基不排水或排水不畅情况下加筋碎石桩复合地基的承载特性,配置了由钠基膨润土和甘油混合而成的新型人工软土地基,进行了4组加筋碎石桩复合地基路堤模型试验,并与排水条件下的试验结果进行对比分析。研究结果表明:加筋碎石桩复合地基沉降随筋材刚度的增大而明显减小,其桩土应力比远大于排水条件下的桩土应力比;筋材刚度较大时,桩体发生向路堤外的整体倾斜变形,而筋材刚度较小时,桩体则发生向路堤内的弯曲变形;部分加筋碎石桩复合地基的沉降明显大于全长加筋情况,且其桩土应力比小于全长加筋时的桩土应力比,但仍大于普通碎石桩的桩土应力比;不同加筋长度碎石桩桩体均在其加筋范围内发生弯曲变形,在未加筋部位发生鼓胀变形;排水条件对加筋碎石桩桩体变形和稳定性有显著影响,排水条件好,桩体弯曲变形小,反之,桩体则产生显著的弯曲变形。通过试验分析得出对于路堤荷载下的加筋碎石桩复合地基,应采用刚度较大的筋材对碎石桩体进行全长加筋,并保证地基的排水,可大幅提高路堤的稳定性。

Model Tests on Bearing Behavior of Composite Foundation Reinforced with Geosynthetic-encased Stone Columns Based on Artificial Soft Clay Technique

A new type of artificial soft clay composed of sodium bentonite and glycerol was made to study the mechanical feature of composite foundation reinforced with geosynthetic-encased stone columns (GECs) in soft clay foundation under undrained or poorly drained conditions. Four groups of model tests of GECs composite foundation with varied reinforcement stiffness and length under embankment load were carried out for this purpose. The test results were compared with those in well drained condition. Results showed that: the settlement of the GECs composite foundation obviously decreases with an increase of reinforcement stiffness. The stress concentration ratio is much larger than that in well drained condition. The columns with high reinforcement stiffness are likely to tilt outward the embankment. The columns with low reinforcement stiffness, however, bend inward the embankment. For the partially encased stone columns, the settlement is significantly greater than the fully encased stone columns. The stress concentration ratio of the partially encased stone columns is smaller than that of the fully encased stone columns, but larger than that of stone columns. The GECs bend inward the embankment in the encased parts and bulge in the non-encased parts. Drainage condition significantly affects the displacement and stability of GECs. Generally, the bending deformation is smaller in the columns with well drained conditions and vice versa. It is found from the study that fully encased stone columns with high reinforcement stiffness and well drained conditions are of great importance to improve the stability of road embankment.