高速铁路硅藻土路基工程现场综合试验研究

Field comprehensive testing on diatomite subgrade of high speed railway

以新建杭绍台铁路通过浙江嵊州及新昌硅藻土地区为研究背景,基于单桩静载、边坡降雨、复合地基承载性能、基床原位激振等现场试验,研究了不同桩型加固硅藻土地基的适宜性、降雨条件下硅藻土边坡变形特性和防护措施、硅藻土桩筏复合地基特性以及基床动力特性。结果表明:CFG桩、素混凝土桩及钢筋混凝土桩适用于硅藻土地基加固,而螺杆桩由于存在挤土效应、高压旋喷桩成桩效果较差不适用;干湿循环作用下硅藻土自然边坡易形成网状裂隙导致浅层稳定性不足,拱形骨架对硅藻土边坡有较好的防护效果,而锚杆框架梁由于钻孔施工易导致硅藻土软化,不适用于硅藻土边坡防护;CFG和素混凝土桩复合地基能够满足硅藻土路基变形控制要求,且素混凝土桩筏结构整体性更好;基床结构中设置毛细防排水板具有良好的防排水效果,保证了水份能够及时排出,避免对基床和硅藻土地基不利影响。

In order to study the suitability of different types of piles for diatomite foundations, deformation characteristics and protective measures of diatomite slope under rainfall, deformation characteristics of pile-raft composite foundation and subgrade bed dynamic response in diatomite, field loading test on single pile, rainfall on diatomite slope, bearing capacity of composite foundation and in-situ dynamic excitation tests were conducted on the Hangzhou-Shaoxing-Taizhou high speed railway. The result shows that CFG pile, plain concrete pile, reinforced concrete pile can be applied to diatomite foundation, whereas the screw pile is inapplicable due to compaction effect and high pressure rotary jet pile due to poor quality effect. The natural diatomite slope has connecting cracks that form network within the slope under drying-wetting cycles, resulting in insufficient shallow stability. The arch-shaped skeleton revetment has a better protective effect on the diatomite slope, while drilling during the construction of anchor frame beam will lead to the softening of diatomite, which is not suitable for the protection of diatomite slope. The CFG and plain concrete pile-raft composite foundation can satisfy the requirement for deformation control, and the structural integrity of concrete pile raft is better between the two types of piles. The capillary drainage layer has a good drainage effect, which ensures that the water can be discharged in time to avoid the adverse impact on the diatomite foundation.