海相淤泥质土中后注浆微型钢管桩浆液扩散及承载特性研究

后注浆微型钢管桩以其施工速度快、场地适应性好及承载力高等技术特点,广泛应用于基础托换及软基加固工程中;然而,针对海相淤泥质土中浆液扩散规律及承载特性的研究仍相对较少。开展连云港海相淤泥质土中静压微型钢管桩及后注浆微型钢管桩承载特性现场试验,对比分析桩侧注浆对微型钢管桩承载特性的影响规律。基于透明黏土材料和PIV技术,开展后注浆微型钢管桩沉桩及注浆过程可视化模型试验研究,观测分析微型钢管桩静压沉桩过程中桩周土体位移场、桩侧注浆施工过程中浆液扩散规律。研究结果表明,现场实测后注浆微型钢管桩竖向抗压承载力约为常规微型钢管桩承载力的2.4倍;静压微型钢管桩沉桩挤土效应小于4.5D,海相淤泥质土中注浆浆液扩散形式以水平向二次劈裂注浆为主。

STUDY ON THE DIFFUSION AND BEARING CAPACITY OF POSTGROUTING STEEL PIPE MICROPILES IN MARINE MUDDY SOIL

Post-grouting steel pipe micropiles are widely used in the underpinning and soft ground reinforcement engineering due to its fast construction, good adaptability and high bearing capacity. However, there is little research on the grouting diffusion mechanisms and the bearing capacity of the micropiles in marine muddy soil. Field tests on the bearing capacity of both grouted and non-grouted steel pipe micropiles in muddy soil in Lianyungang were carried out. The influence of post-grouting on the bearing capacity of the steel pipe micropiles was evaluated. Based on the transparent clay and the particle image velocimetry (PIV) technique, visual model tests on the construction process of steel pipe micropiles were conducted. The displacement of surrounding soil and side-grouting diffusion in transparent clay were measured and discussed. Field test results show that the bearing capacity of the grouted micropile was improved to nearly 2.4 times compared to that of the non-grouted micropiles. It also shows that the maximum influence range of the pile installation in the horizontal direction was about 4.5D from the center of the micropile;and grouting diffusion in the muddy soil mainly belonged to fracture grouting in the horizontal direction.