Vehicle Dynamic Load Under Slab Beneath Loess Dark Hole Stability Analysis

As the most popular and basic transportation mode in the modern life, highway transportation is taking irreplaceable place all over the world. When building highways in the loess areas, owning to its typical regional characters and specific properties of loess itself, many highway engineering geology disasters appear during the course of construction or in the process of service. It not only affect the design, construction and maintenance of the highway to great extent, but also become main menace to safety and efficiency of its service. In view of their great harm and wide occurrence, most of these disasters are studied in time, but for a long period, the research on the hidden holes in loess is neglected.Usually, highways in the loess plateau are directly built on the loess layer, therefore, it is very common to cause potential threaten to highway. On the one hand there may be transportation interruptions directly leaded by damage of highway, on the other hand, because damages of the loess holes possess paroxysmal feature, severe traffic accidents happen frequently or even many people are killed in it.The formation, development and collapse of hidden holes under pavement of highway are a long dynamic process in the loess areas. As to the highway, a practical system, vehicles are its main service objects, so dynamic load of the vehicles become the main load subjected by the highway. After the hidden holes under the pavement come into being, though it can't lead to the collapse of the highway in the earlier period, stress concentration can cause the yielding destroy in the surrounding areas of the holes, which will make diameter of holes bigger and depth shallower, and all of these help to stress concentration and collapse of surrounding earth. Obviously, it is a vicious circle, the complete collapse will be the last result. Hence, the researches on the harms to the pavement of the hidden holes under the dynamic load, especially on the depth and width of harm, have the significant practical meaning for the election of disposal methods and the forecast of harm degree.First, make the dynamic testing of 12 groups of original state loess samples collected at Longxu Shanbei and Guanzhong. Experiments mainly include dynamic elasticity modulus and dynamic intensity testing. In the former testing, on the basis of the statistical analysis to the testing records, the dynamic elasticity modulus and damping ratio parameter of loess pavement used for finite element method are determined. In the latter testing, intensity parameters such as dynamic cohesion and dynamic inner friction angle are gained.Second, using the finite element method, make the elastic-plastic numerical analysis on dynamic response and stability of the hidden holes under the dynamic load. As the main affecting factors, the speed of the vehicle, the diameter of the hole, depth and excursion distance are taken intoaccount, and find the law of their critical values. In addition, in order to ascertain the effect of the direction and shape of the hole, use different model to make contrast.Last, on the basis of the calculation and the analysis, analyze the forecast calculation method for critical depth of the hidden holes in loess, and use VB 6.0 to compile the programme LDMC including parameters: diameter of the hole and excursion distance. Finally, realize the graph-alternating interface.