Research On Shaking Table Test Of The Liquefiable Ground Treated By Compaction Sand Piles

The newly-built Kunming-Hekou railway, which starts from Kunming of Yunnan Province to Hekou with a total length of 380 km, is the trunk line that connects China and Vietnam, as well as Southeast Asia. There is large area with saturated silty-fine sand ground along the Kun-He railway. Most of them located in 8 degree earthquake region, and the ground is liquefiable under earthquake. The lateral flow of the liquefiable ground and the embankment settlement caused by liquefaction are the main reasons for the possible serious damage for the railway.Compacted Sand pile has been widely used in liquefiable ground due to its effectiveness and adaptability. At present, some mechanism about anti-liquefaction of sand pile has been studied, but it is still quite limited. The design and anti-liquefaction judge in practical engineering mainly focus on the effect of densification, either it is too conservative or the risk of liquefaction still exists.In view of this situation, A typical section of kun-he railway is selected as Prototype, having developed a 1:10 scale shaking table model test on sand pile used in consolidating silt foundation. By loading different levels of sine wave on the model to obtain the pore pressure, displacement and acceleration response curves, combined with the macro performance of model in the test, and some conclusions are gained as followed.1. From 0.05g to 0.2g in the loading process, the foundation of the pore pressure, settlement, subgrade deformation are very tiny; when 0.25g load, part of the foundation soil liquefies, pore pressure, settlement and deformation are very obvious; for the 0.3g load, most of the foundation soil liquefy, from the embankment slope at the foot of the slope outside the extrusion forming small sand dune, the embankment has a big settlement, deformation or even destruction.2. When the 0.3g is loaded, deep pore pressure rises up to 5～7kPa, but the shallow pore pressure is only 2～3.5kPa; now foot just below the foundation subgrade soil, the deep pore pressure ratio does not exceed 0.5, while the shallow pore pressure ratio reaches to 1.5, which means that it has been completely liquefied. In other words, in the loading process, the excess pore water pressure increases with depth, while the pore pressure ratio decreases with depth.3. Between the left and right shoulder area below ground in soil pore water pressure than the maximum Department has not more than 0.4, the same depth of the roadbed outside the maximum pore pressure ratio exceeds 1.7, this is because the weight of roadbed, inhibiting the foundation soil the trend in the liquefied.3.The pore pressure ratio of the ground soil between the left and right shoulder area has not been exceeded 0.4, while the pore pressure ratio of other place exceeds 1.7, although with the same depth.. It can be explained that the liquefaction trend of the ground soil has been restrained, due to the weight of ground soil.