Study On Soft Soil Foundation Treatment And Settlement Prediction Of A First-Class Highway

The highway transportation is widely used in China. The soft soil foundation as an important part of road construction, the embankment built on it’s prone to unstable and uneven settlement and its damage may lead to traffic safety and even traffic accidents. In order to overcome the bad properties of soft soil which cause the damage of subgrade, the appropriate ground treatment should be adopted. It can significantly improve the bearing capacity of soft soil and satisfy the engineering requirments.This paper mainly makes a deep research on the treatment and settlement prediction of soft soil foundation based on the domestic and foreign achievements, and the concrete work is as follows:1. Relying on the project of Lan Yong first-class highway(Lanzhou Xincheng to Yongjing hyper channel which along the Yellow River), analying the foundation with dumping riprap to extrude silt was based on the finite element analysis software PLAXIS.Acomparison with numerical simulation results and the monitoring results were made and the simulated results are in good agreement with the data of monitoring.2. FEM analysis software of PLAXIS was used to simulate the soft soil foundation treated with dumping riprap to extrude silt based on the field test section. The bearing capacity of treated soft soil foundation improved and the settlement and horizontal displacement met the design requirement. The composite modulus is larger and the integrity of treated foundation is stronger. The pore water pressure is decreased and the consolidation of foundation is accelerated after treatment.3. The parameters of riprap modulus and width and thickness of stone riprap were analyzed by finite element analysis software PLAXIS. The influences of parameters on treated foundation were envaluated in terms of the subgrade settlement factor. The subgrade settlement decreases with the increase of the riprap modulus and width and thickness of stone riprap. Since the subgrade settlement changes irregularly with the thickness of backfill sand, it can be chosen according to the actural situation and local experience.4. According to the settlement observation datas of consolidated soft soil foundation of Lanyong first-class highway, the hyperbolic method, exponential curve method, power polynomial model and prediction method of Asaoka are used to predict the settlement of foundation. Comparing the fitting results with the measured data, it shows that all methods can be applied to predict the settlement of the actual project, futhermore, Asaoka prediction result is the best proximate. Finally, comparing the prediction results based on selecting different time interval to get equal time interval about Asaoka method, get a reasonable time interval value. The advised value is 30 d.The above investigations show that the dumping rockfill and extruding silt can improve the bearing capacity of treated soft soil foundation and the mechanism is clear. Considering a series of advantages of this soft soil treatment method such as simple, rapid and economical, it is worth popularing and widely applying. The Asaoka method can be used to predict the settlement of foundation effectively according to the analysis of settlement prediction. The advised value of equal time interval of Asaoka method is given based on the simulation results, which provides a reliable basis for the structural design and engineering application.