Study On Stress Character Of Prestressed Anchorage In Different Regional Antiknock Chamber Effected

To study force characteristics of pre-stressed anchor (freestyle, full-length bond-type and semi-full bond-type) in the antiknock chamber effected by concentrated explosive charge, the geo-mechanical model for researching antiknock properties of the anchor chamber in the "Test device of geotechnical engineering antiknock structure model" is tested. The numerical analysis model was established by the use of explicit finite difference algorithm for learning of the antiknock reinforced effect of prestressed cable, and the stress characteristic of prestressed cable in different site of antiknock chamber is analyzed. And the reinforced design factor is analyzed for the semi-full bond-type cable. Finally, the analytical solution of the dynamic response of anchorage chamber is shown to make appropriate project proposal. Main tasks are as follows:1. According to the similarity theory, the research contents and the assumptions of the antiknock model test, the mechanical parameters of rock mass, cables as well as grouting material, and the size of chamber model were determined. The equipment composition and the function index of "Test device of geotechnical engineering antiknock structure model" is described briefly. After blocking, the production of the simulated cable, the installation process and the associated model test technique were overviewed. The sensor technology in testing system was illustrated mainly from the aspects of the pressure sensors, acceleration sensors, the relative displacement sensors, cable tension sensor, and anchor body axial deformation tests. For describing the reinforcing effect of anti-conventional weapons anchored chamber more completely and vividly, the research was done from several observing angles such as the statistics of the shedding area of the anchorage, the failure video of the chamber and so on.2. Through 3 groups of antiknock structural model test, the wave curve of the wall-rock pressure of the anchorage chamber, the relative displacement from top to bottom, the surface strain of the tunnel wall, and the acceleration of roof and floor is gain to analysis. And then, the antiknock performance of the prestressed anchorage chamber was studied. And, the peak attenuation low of the free-field stress and the propagation velocity of wave were fitted. By analyzing the time history of the axis strain and the tension of the cable end in the vault and the side wall in different experiment plans, the dynamic response and the failure mechanism of the prestressed cable under the condition of the top explosion were researched.3. Useing the finite difference software FLAC^3D to building the analysis of freestyle prestressed cable reinforcement chamber model, the explosion cavity-rock-structure interaction model for numerical analysis methods were discussed, and the calculating reliability were contrasted to the model test results. The results show that:to reserve spherical explosion chamber and impose the initial normal stress method could realize the effect of explosive detonation in the dynamic analysis module; Hawk-Brown model can be used for dynamic response analysis of plain concrete; imposing the static boundary conditions could treat with a small model analysis such as antiknock structural model test; the element mesh is the highest frequency corresponds to the 1/10 length of the wavelength to ensure the full uniform mesh; the gravity acceleration is adopted to achieve dynamic load added to the calculation model; using of Rayleigh damping could realize the process of blast wave propagation effects.4. The anti-knock ability of chamber supported by freestyle anchor, full-length bond-type anchor and semi-full-length bond-type prestressed anchorage cable are examined by numerical analysis. Some sets of numerical experiment for the bond-type anchor reinforcement parameters including internal anchorage length, elastic modulus of anchor grouting, anchor spacing and layout were done, to obtain the reasonable value range design parameters of bonding prestressed anchorage cable, and refer to engineering design.5. The basic conception about the dissemination in two kinds of media and the reflection and refraction on the free sub-interface of stress pulse were described. Based on the basis of traveling wave energy absorption method, the formula of allow tension increment of anchorage cable under condition of the blast wave shock is derived. The "drag" role of prestressed anchor interior bond section in the model test is analyzed systematically, which is caused by resistance of rock thrown during exploding into a pit.