Ⅳ级自重湿陷性黄土区客运专线铁路路堤处理地基的现场试验研究

试验段为自重湿陷性Ⅳ级黄土场地，分3种不同地基处理措施试验分区，分区之间设地基不处理过渡段。柱锤冲扩桩段对22 m深湿陷性黄土层全部处理，水泥挤密桩段仅处理上部15 m深湿陷性黄土层，强夯段处理上部6 m深湿陷性黄土层。结果表明，处理深度范围内黄土的湿陷性已消除，地基承载力均大于标准值。柱锤冲扩桩与水泥土挤密桩复合地基沉降量小于15 mm，满足高速铁路对工后沉降量的要求，而强夯地基的沉降量不满足要求。柱锤冲扩桩区段，桩间土的最小和平均挤密系数不低于0.88和0.93的标准，但是桩身平均压实系数和压缩模量却分别低于0.97和100 MPa的标准。水泥挤密桩区段，桩间土的最小和平均挤密系数、桩身平均压实系数和压缩模量也低于同样的标准值。强夯地基的压缩模量小于15 MPa的标准。检测标准的合理取值有待深入研究。

Field test research on treatment effect of embankment foundation in class Ⅳ dead-weight collapsible loess zone along railway passenger dedicated line

The experimental section is located in the class Ⅳ dead-weight collapsible loess site and is composed of three different kinds of loess foundation treatment measures. The transition sections without foundation treatment exist between them. All 22 m depth of collapsible loess is treated in zone of piles with down hole dynamic compaction. The upper 15 m depth of collapsible loess is treated in zone of cement soil compaction piles. The upper 6 m depth of collapsible loess is treated in zone of dynamic compaction. The results show that the collapsibility of loess within treatment depth has been completely eliminated. Their bearing capacity is higher than the standard value. The composite foundation settlements of piles with down hole dynamic compaction and cement soil compaction piles are less than 15 mm after construction for high-speed railway; but the dynamic compaction foundation can not meet the same requirement. In zone of pile with down hole dynamic compaction, the minimum and average coefficients of compaction are respectively more than the standard values of 0.88 and 0.93; but the average coefficient of compaction and compression modulus of piles are respectively less than the standard values of 0.97 and 100 MPa. In zone of piles with cement-soil compaction piles, the minimum and average coefficients of compaction, or the average coefficient of compaction and compression modulus of piles are also less than the same standard values. Average compression modulus of dynamic foundation is less than the standard value of 15 MPa. The reasonable values of test standard need further study.