A Study On Application Of Foamed Light Soil In Reinforcing Deep Soft Soil Founfation

Oversized deep soft soil which is of high compressibility, low permeability and strength distributes widely in the east of China. Then the high speed railway built on this kind of foundation occurs differential settlement, which the safety and stability are deeply influenced. Grouting is widely applied to reinforce the railway foundation. However, more settlement occurs after reinforced by conventional grouting materials, which the engineering problem can’t be solved fundamentally.Based the above, the preparation, influence factors and reinforcement effect of the new lightweight grouting materials called Foamed Cement Banking are researched for providing advanced material and new reinforcement method to improve the engineering properties of soft soil foundation. The main conclusions gained are as follows.1. Applying a series of proportion and orthogonal test, the optimum proportion which the requirement of density and strength can be meet is gain. Water cement ratio is 0.5, solution concentration of foaming agent is 0.5%, mass percent of coal ash is 10%, and the volume ratio of the foam and cement grout is 1:1. For influencing the density and compressive strength of the foamed cement banking, the proportion of different factors is as follows:the volume ratio of the foam and cement grout>water cement ratio>mass percent of coal ash> solution concentration of foaming agent.2. By researching on the long-term strength, long-term density, drying and watering cycle characteristics, acid-base resistance property, and liquidity of foamed cement banking, the foamed cement banking is of characteristics of durability, lightweight and high strength.3. The grouting materials made by the optimum proportion are applied in the model test. From the test, the soil lateral pressure decreases with the increasing of the distance from the injected hole under the same grouting pressure. The higher grouting pressure is, the bigger soil lateral pressure is, and the more obvious the uplifts of surface of the soft soil are.4. When the grouting pressure is not high (0.2MPa、0.4MPa), the compaction grouting occurs in the soft soil foundation. And when the grouting pressure gets 0.6MPa, split grouting happens.5. Under different grouting pressure, the density of grout located at the opening of the injected hole is minimum, and increases with the development of the depth of injected hole. And the density of the grout increases with the increasing of the grouting pressure.6. Comparing the density and the compressive strength of the standard test blocks which is cured for 7 days, and the columnar solids, the compressive strength of both is of intensity difference, but the densities are almost same. For every grouting pressure, the compressive strength of columnar solids is all smaller than the standard test block’s. And the maximum difference occur the grouting pressure of 0.2MPa, For the 0.4MPa grouting pressure, the difference is the minimum.