有改良层既有线过渡段承载特性及加固研究

Study on the Bearing Capacity and Reinforcement of an Existing Transition Section with Improved Layer

既有线路桥过渡段存在的路基承载力不足的问题普遍存在,对其进行检测、路基承载性能评估对保证列车安全、平稳运行尤为重要。通过E_(vd)、动力触探及粘贴应变片等原位测试手段,对某既有线过渡段水泥改良表层而下卧软弱土层的路基构造承载特性进行研究,并对水泥挤密桩加固效果进行评价,得到结论:(1)路桥过渡段距桥台0~5 m区间是线路最薄弱环节,需重点加固保护;(2)基床表层水泥改良层厚度对路基承载力影响显著,轨下E_(vd)值远大于路肩E_(vd)值,最大差值高达45.79 MPa;(3)水泥挤密桩改善既有线路桥过渡段路基承载性能效果良好,加固后过渡段刚度显著增大,动土压力则明显减小。

The insufficient bearing capacity of the existing bridge transition section remains a widespread problem and E（vd） dynamic penetration test and adhesive strain gauge field test are employed to study the special bearing characteristics of an existing line bridge transition section with modified cement surface and underlying soft soil layer,and to evaluate the effect of cement compaction pile. Some conclusions can be drawn as the following：（ 1） the section of 0 - 5m between the bridge transition section and the abutment is the weakest link and should be reinforced and protected;（ 2） the roadbed bearing capacity is significantly affected by the thickness of the bedding surface layer with modified cement layer,the E（vd） value under the rail is much larger than that of the shoulder E（vd） with the maximum difference up to45. 79MPa;（ 3） cement compaction pile plays an active role in improving the existing line bridge transition section subgrade bearing capability, and the stiffness values increases significantly after reinforcement,and the dynamic earth pressure decreases obviously.