Papers by Author: Nai Wang

Abstract: Based on Mohr - Coulomb failure criterion, dynamic strength characteristic of undisturbed loess in Xining, Lanzhou, Xiji and Xian was studied through dynamic triaxial test. And the regional characteristics of void ratio, natural moisture content, plasticity index and dynamic shear strength with different vibration frequency and natural conditions were analyzed. The research shows that dynamic shear strength of loess increases when consolidation stress rises under the same water content condition. However the increase trend is not proportional relationship. Initial void ratio and water content of loess under natural state rises from northwest to southeast, and dynamic cohesive force enhances. On the contrary, internal friction angle decreases with the change of characteristic. With the increasing trend of disturbed loesss clay content from northwest to southeast, dynamic cohesive force increases and internal friction angle decreases in the different amplitude. The conclusion enriches and develops the evaluation theory of loess regional dynamic characteristic and it is a universal method to reduce cost of different loess regional classification.

Abstract: The problems of compacted loess roadbed utilization are closely related to the characteristics of compacted loess and long-term vehicle loads. According to the characteristics of compacted loess in different degree of compaction, the distribution and deformation change rules of the dynamic stress under dynamic load are studied through the finite element program numerical analysis of vehicle loads roadbed dynamic response. The data is acquired by field test and laboratory experiment. In lighting of the influence of the subgrade deformation by degree of compaction and pavement structures, the influence models are given which are used for estimating the roadbed vertical displacement in different conditions.

Abstract: Environment pollution and exhaustion of mineral resources aroused strongly research and development of fly ash utilization. As a kind of foundation treatment method, improved by fly ash is more and more used in highway, railway roadbed construction. With the increase of speed of vehicles and vehicle load, the influence of dynamic load on the subgrade has caused people's concern. In this paper, based on fly ash modified loess, dynamic property of modified fly ash loess is discussed through the dynamic triaxial test of the unsaturation disturbed loess. The effect of the dynamic elastic modulus and the damping ratio with different amount of fly ash loess is studied. The results show that the difference of dynamic properties in dynamic load and static load is large. It mainly presents the hysteresis quality and nonlinear relationship between dynamic stress and dynamic strain. And the dynamic elasticity modulus increases with fly ash mixed amount.

Abstract: The structural property is an important influence factor in loess liquefaction, which contains the interaction between the soil granules. According to study by Gao, the loess could be divided into three types as weak cemented loess, half cemented loess and cemented loess based on the grain composition, the consolidation and the weather conditions of the loess when it formed. In this paper, based on microstructure test and dynamic triaxial test of the loess from the Loess Plateau region, liquefaction properties of structural loess was analyzed. The results show that: (1) the structural strength of loess of weak cementing type, half cementing type and cementing type increases in order, and so does the liquefaction strength, (2) the change mechanism of different structural loess’s dynamic strain during liquefying is different, (3) the change of saturation loess’s pore water pressure during liquefying is related to the type of pore and the structural strength.