大型石化地基振冲碎石桩处理现场试验研究

针对大型炼厂工程地基处理的复杂性，开展了振冲碎石桩的现场试验。利用静力触探试验检测桩体密实度和判别饱和砂土液化。基于旁压试验、标准贯入试验和重型动力触探试验结果，分析了施工前后地基承载力和土体工程特性变化情况。以单桩和复合地基载荷试验结果验证了桩间土、单桩及复合地基的承载性能。研究结果表明，振冲碎石桩对桩长范围的砂土具有明显的挤密效应，工程特性和场地的均匀性在处理后有了明显改善和提高，有效地消除了桩长范围内砂土的液化可能性。静载荷试验结果表明，振冲碎石桩复合地基承载力能达到设计要求；振冲碎石桩对砂土层下卧黏性土层的加固作用不明显，部分深度范围内土体强度降低；当地面以下10 m内不存在厚度大于5 m的软土夹层时，较薄的软土夹层状对挤密加固其余深度的砂土未产生明显影响，对地基承载力影响亦较小。

In-situ test on vibro-replacement stone pile in large petrochemical foundation treatment

Foundation treatment of large-scale refinery is very complex. In view of this condition, in-situ test of vibro-replacement stone pile was carried out. With static cone penetration test dynamic penetration, pile density was detected and saturated sand liquefaction was judged. Based on results of pressuremeter test, standard penetration test and heavy dynamic penetration test, foundation bearing capacity change and soil engineering characteristics change during construction process of vibro-replacement stone piles were analyzed. The bearing capacity of composite foundation was evaluated by static load test of single pile and composition foundation. The results show as follows. Firstly, vibro-replacement stone pile has a compaction effect on the sand soil of pile length range. Engineering characteristics and field uniformity has been improved apparently. Sand liquefaction possibility for pile length range can be eliminated. Secondly, static load test results show that the bearing capacity of composite foundation has reached the design requirement. Thirdly, the compaction effect on clay soil, which is under sand soil layer, is not apparent. And soil strength in some depth range even reduces. Finally, the bearing characteristics will not significantly be affected when no more than 5 m thickness of soft soil interlayer exists 10 m depth below the ground surface.