郑西客运专线湿陷性黄土区试验路堤的沉降观测与预测研究

郑西客运专线路堤工后容许沉降量为15mm,湿陷性黄土区路堤地基处理的沉降控制是关键性技术难题,为此,选择湿陷性黄土代表性地段进行了不同地基处理措施路堤工程沉降观测试验研究。研究结果表明,路堤本体的压缩沉降量只有3mm,并在路堤竣工后的15d内趋于稳定,路堤沉降主要由地基沉降控制,而地基沉降则决定于3种不同地基处理措施层以下土层的沉降量大小。在沉降量大小、地基处理和浸水效果方面,22m深湿陷性土层全部处理的柱锤冲扩桩区段最好,15m深湿陷性土层的挤密桩区段较好,6m深湿陷性土层的强夯区段最差,而且采取合理的防排水措施防止坡脚附近积水浸泡非常必要。采用双曲线法、三点法和Asaoka法预测结果的平均值作为路堤的最终沉降量,柱锤冲扩桩区段、挤密桩区段的路堤分别需要恒载预压5个月、8个月便可卸除荷载铺设无碴轨道,强夯区段路堤的预压荷载可能需要持续很长的时间。

Settlement observation and prediction research of test embankment in collapsible loess area along Zhengzhou-Xi'an passenger dedicated line

The Zhengzhou-Xi'an passenger dedicated line allows 15 mm settlement of embankment after acceptance. The settlement control of ground treatment in collapsible loess is a key technical problem. Therefore, the settlement of an embankment construction on ground treatment with different measures is observed and researched experimentally in a selected area of typical collapsible loess. The results show that the compression settlement of embankment body is only 3 mm and have already stabilized in 15 days after completion of embankment. The embankment settlement is primarily controlled by the foundation settlement which is determined by the settlement of soils below three different kinds of ground treatment layer. A section of pile thrusted-expanded in column-hammer which treats all 22 m depth of collapsible loess is best, a section of cement soil pile which treats 15 m depth of collapsible loess is better, a section of dynamic compaction which treats 6 m depth of collapsible loess is worst in the settlement, ground treatment and immersion effect. It is very essential that the reasonable waterproof and drainage measures are taken to prevent water from immersing the vicinity of slope foot. The average value of results which are predicted by the hyperbolic method, three-point method and Asaoka method is used as the final settlement of embankment. The constant preloading can be removed to lay ballastless track after 5 months in the section of pile thrusted-expanded in column-hammer and after 8 months in the section of cement soil pile. But it may need to continue for a long time in the section of dynamic compaction.