Model Experiment Of A Rock Bedding Slope During Excavation

With the constant development of the western region, water conservancy and hydropower engineering, mining engineering and transportation engineering are developing rapidly. Going with the constructions, it involves a great amount of excavation, which forms many steep slopes with great obliquity. And it may usually causes deformation and instability phenomenon to these slopes, in which the bedding rock slopes are in the majorities. Therefore, there is important guiding significance to the projects that making deep study of the engineering properties of the bedding rock slope, during the excavation process.Aim at the characteristics of bedding slope,and combine the methods of theoretical analysis,model test and numerical simulation,this paper has conducted systematic research of the bedding slope,which is mainly about the classification,failure mode and deformation mechanism,and the laws of the displacement and stress change and the arising damages of the excavation process.The main results achieved are as follows:1. Base on the actual survey and geological investigation reports,bedding slopes are divided into two major categories: bedding rock slopes and composite geotechnical type),and six minor categories2. Base on the various different combinations of rock's quality and composition,structure,mass strength,structural plane spacing,the relationship between Structural plane trend and the slope's,also between Structural plane inclination angle and angle of slope,this paper has analyzed the possible failure modes case-by-case,including the overall slide,bedding slide,wedge slide and so on.3. In view of the two typical failure modes: slide damage and collapse,on one hand,analyze the tresses of single- or multi-layer rock mass; on the other hand,set up the sliding damage limit-equations respectively,as well as the flexor curve differential equations of collapse.4. Use the object of the typical bedding rock slope,make materials which is similar to the rock in mechanical properties. Besides,design an advanced reaction system to simulate the road section slope internal stress condition.5. Carry out the excavation model tests in three stages,measure when excavate processes. Then discuss the laws of displacement and stress change. Five hours after the first stage,the displacement in the direction of the free surface is relatively obvious. Then it tends to converge basically in four days followed. However,stress varies greatly when unloading,and is not always to reduce at some measuring point,but seems to be unstable sometimes. It may due to the stress transfer between adjacent points,but presents decreasing trend eventually. The stress convergence is a long-term process. The second and third stages are basically the same as the first,only offers the less quantity of value change in displacement and stress.6. The numerical analysis using FLAC3D is employed to an actual project during excavation,Compare the simulated changes of displacement and stress with the model test's result,we can see that the development trends of displacement and stress are basically the same as the excavation proceeded,but smaller value than model test. When compare the maximum principal stress of the corresponding point with the minor,we can draw that results of vertical simulation is smaller than the actual measurement by 3 to 5 times.7. After the three stages,the stress concentrates on the toe of slope,and slide damage happens in the second layer of the rock,also emerges crack extension at the after skirt of the slope,which is consonant with the macro-phenomenon of construction site. From the FLAC3D simulation figures,crack extension occurs at the after skirt of the slope,and slid damage at the inter-layer.