DDS桩在高速铁路复合地基工程中的适用性

结合铁路建设工程实际,选择不同地质和工况条件的施工区段,对DDS桩(全螺纹灌注挤土桩)和CFG桩(水泥粉煤灰碎石桩)进行复合地基载荷试验,对比分析2种桩在复合地基加固效果上的差异;对DDS桩进行实体取芯、局部开挖,研究其未达到预期效果的原因.结果表明:地质条件、工装设备和工艺直接影响DDS桩的成桩质量和加固效果;桩底和桩身螺纹质量是保证复合地基处理效果的关键;在承载力以短桩端承力为主的加固区段不宜采用DDS桩技术进行复合地基处理;在承载力以长桩摩擦力为主的加固区段可采用DDS桩技术,但须采取改进措施.

Adaptability of DDS Pile to Composite Foundation Projects on High Speed Railway

Combined with the actual situation of railway construction engineering,the construction sections with different geological and working conditions were selected to carry out composite foundation load tests on drilled displacement piles with a screw-shaped shaft(DDS piles)and cement fly-ash gravel piles(CFG piles).The difference between the two kinds of pile composite foundation reinforcement effect was analyzed,solid coring and local excavation was carried out for DDS pile,and the reason why DDS pile fails to achieve the expected effect was studied.The results show that geological conditions,tooling equipment and technology directly affect the quality of DDS pile and the effect of reinforcement,the quality of screw thread of pile bottom and pile body is the key to achieve the effect of composite foundation treatment,DDS pile technology should not be used for composite foundation treatment in the reinforcement section with short pile end bearing capacity as the main bearing capacity,DDS pile technology can be used in the reinforcement section with long pile friction as the main bearing capacity,but the measures must be improved.