Study On A Determination Method For The Compactness Of Soil-rock Mixture Subgrade Based On Static Penetration Test

In the mountain area, the subgrade is usually filling by soil-rock mixtures. Because of the complexity of material composition and irregular of structure distribution the compactness of soil-rock subgrade must be controlled for improving the quality of subgrade filling.Meanwhile, the method which can quickly and reliably detect compactness of soil-rock mixture subgrade must be established.The method for detecting compactness of soil-rock mixture subgrade include water (sand) replacement method,wave method and static penetration method by now. However,there are dificiencies and limitations since the accuracy of these above methods is poor or the efficiency is low, which are unable to meet the requirements of soil-rock mixture subgrade rapid construction. Therefore,eatablishing the rational method for detecting compactness of soil-rock mixture subgrade is the key problem to control the compaction effect of the soil-rock mixture subgrade. In this paper study on this problem combined with related projects has important practical values for theory and engineering.On the basis of comprehensive analysis of the present compactness detecting technology of soil-rock subgrade, firstly, according to discuss the static penetrating deformation process and its mechanical mechanism of soil-rock subgrade in the process of static penetration test, it's regarded that the deformation of the subgrade under static penetration load was composed of the compressing deformation of the soil-rock column and the settlement of its column end,considering the regularity that the porosity ratio and deformation modulus were changed when the soil-rock column and the soil-rock mass of the column end were compressed under static penetration load, a theoretical model of calculating the deformation of the soil-rock column and the column end was set up by adopting the idea of step loading. Thereby, a model of the relationship among the static penetrating deformation and penetrating load and subgrade's initial porosity was established. Secondly, according to the static penetration load test curves which was generated by the static penetrating, a method of back analysis of the subgrade's initial porosity was developed by the use of adaptive simulatied-annealing algorithm which composites the advantage of annealing algorithm and genetic algorithm according to the demand of the method of optimizing back analysis of this article,then, the compactness of soil-rock mixture subgrade was determined according to the relationship of the subgrade's initial porosity and compactness, consequently, a method of detecting the compactness of the subgrade was set up. Finally, the practical engineering analysis indicates that the compactness determination method proposed in this paper is feasibile and reasonable.