Properties Of Silt Embankment In Anhui Province

Anhui, Henan and Shandong Provinces are located in the Yellow River Flood Plain, where the low liquid limit silt or silt-sand-based soil deposition is widely distributed. Due to special physical and mechanical properties, Silt has high coefficient of permeability, permeability properties of strong consolidation, drying form of powder and can be shaped only in conditions with certain water content. With the high silt content, uniform particle size, developed capillary, stability of poor water, and frozen sensitive, the silt is not suitable to be the material of soil sub-grade. But along with the rapid development of highways, more and more silt filling has been used for embankment construction.One comprehensive survey of silt embankment under construction and constructed is carried out to study the performance of the silt used for road construction in this paper, which includes the situations of design and operation of the embankment. The emphasis of the study is mainly based on the Si-Xv highway under construction in Anhui Province. In accordance with the previous research results and practical engineering experience, the analyzed methods of the theoretical analysis, laboratory test and finite element simulation method are adopted separately to study the behavior of the silt embankment. The main contents contain as follows:1. According to the actual conditions of the embankment soil layers, the conventional tests of the physical and mechanical properties are carried out on the silt soil with different degree of compaction. And indexes such as the maximum dry density of powder, the particle size distribution, the direct shear strength, the unconfined compressive strength are obtained separately. In addition, it is hard to obtain the standard hard silt soil samples using the conventional sampling method in course of unconfined compressive strength test. Consequently, a special soil preparation equipment is designed and developed in our experimental laboratory.2. Considering the special physical and mechanical properties of the silt, the experiments of freeze-thaw cycle and dry cycle about silt are separately performed, and the strength distribution of the silt after freeze-thaw cycle and dry cycle changes is obtained.3. Dynamic Tri-axial test is performed to obtain the relationships of vibration frequency and dynamic stress, and dynamic elastic modulus and damping ratio characteristics of the dynamic stress.4. In this paper, the highway traffic loading model, sub-grade model and the corresponding dynamic stress responses are separately analyzed. Meanwhile, the failure mechanism of the highway embankment is studied in the finite element method using finite element software PLAXIS. The simulation of short-term car load is considered as the following cases in accordance with the different sub-gradient of silt embankment:a) Normal state of silt embankment b) The silt embankment after the freeze-thaw cyclesc) The silt embankment after the wet-dry cycles5. By the finite element analyzing, the maximum displacement and safety factor of the various states depicted above, and the recommended value of silt embankment slope, the influence depth of the vehicle load are obtained.