Study On The Anti-detonating Characteristics Of Underground Opening Reinforced By Rockbolts

Modern warfare has transformed into an information warfare age that is provided with nuclear deterrent conditions. The precision-guided penetrating underground weapons are developed quickly towards high strength, penetrating more deepness, great equivalent and minitype nuclear weapons state. This condition has seriously intimidated the safety of protective projects, such as the underground hospitals and storages Therefore, it is a realistic and strategic significant research to carried out the anti-detonating characteristics study on the reinforcement technology of the surrounding rock of protective projects when these projects are attacked by the penetrating weapons. This dissertation will make use of the research methods of model experiments of geomechanics, numerical simulation and theoretical analysis to study the anti-detonating characteristics of underground opening reinforced by rockbolts under the conditions of focus charging. The main contents are as follows:1. The wave curves of vertical stress, horizontal stress, surface strain of underground opening wall, accelerations of roof-to-floor and sidewall and the relative roof-to-floor displacement are obtained by carrying out model experiments of geomechanics. The characteristics of these curves are as follows: The time of positive pressure of vertical stress of measuring points of vault's and sidewall is relative long. But the time of positive pressure of horizontal stress of sidewall is relative short and the wave curves' fluctuation is very big. The wave curves of surface strain show the majority strain is tensile strain of vault's measuring points. But the other measuring points is compressive strain. The largest strain of every underground openings is located in the spring of arch. The accelerating wave curves of vaults' measuring points don't fluctuate. However, the accelerating wave curves' fluctuation of the floor is relative big, and these curves reach their peak value for a few milliseconds. The fluctuations of the wave curves of the roof-to-floor relative displacement isn't big, and these curves become stabilization at their residual strain at last.2. When the underground openings are reinforced by the different kinds of rockbolts, their anti-detonating characteristics should be manifested by the differences of the peak value of stress of surrounding rock and its attenuating rule, strain of surface wall, acceleration of roof-to-floor and sidewall, displacement of roof-to-floor and the macroscopic damage forms of every underground opening. By comparing individually the vertical stress in surrounding rocks of underground openings reinforced by normal rockbolts, by the short and dense rockbolts, by the short and dense lengthened rockbolts at the spring of arch, the vertical stress of surrounding rocks of underground openings reinforced by the long and dense rockbolts, by the long and short alternating rockbolts, by the long and dense lengthened rockbolts at the spring of arch is relative large, and their stress attenuating coefficients are relative small, their damage cracks generate out of the reinforced zone, and there is no cracks in the reinforced zone. By synthetical comparison of stress of surrounding rock, strain of surface wall, acceleration of roof-to-floor and sidewall, displacement of roof-to-floor and the macroscopic damage forms of every underground opening, the result shows the anti-detonating characteristics of the underground opening reinforced by the long and dense lengthened rockbolts at the spring of arch is the best. When the reinforced type of rockbolts and charge mount is known, stress of surrounding rocks,acceleration and displacement can be forcasted by the fitting equations of stress,acceleration and displacement.3. LS-DYNA3D program is used to build the corresponding numerical model of the first explosion of model experiment and numerical simulation is carried out. Vertical stress wave curves and vault's displacement wave curves of the surrounding rocks of underground openings are obtained. The results indicate that the forms of stress wave curves obtained by numerical simulation and measuring are similar, and the trend of stress waves' propagation is consistent. By analyzing the peak value of vertical stress and displacements of vaults' surrounding rocks, stress of all the reinforced underground openings' surrounding rocks is larger than that of the underground opening unreinfoced by rockbolts. The variable rules of the vertical stress of surrounding rocks and its attenuation and the displacement's changing are consistent with that of model experiments. By using the methods of fix individually interval and length of rockbolts are adopted, the proper rockbolts' interval and length which can enhance the anti-detonating characteristics of underground opening are obtained when charge amount is 100g and explosive center is located in the distance of 83cm right overhead the vault, and this result has a reference value of reinforcing the surrounding rocks of protective projects and tunnels.4. According to the hypothesis of elastic waves of SH-wave which exists in explosive stress waves, the method of conformal mapping of complex function at unit circle is used to solve wave equation. The shear stress in surrounding rocks of underground opening caused by incident SH-wave and scattered SH-wave is obtained. By time-frequency analysis, the distribution rule of dynamic stress concentration coefficient under the action of the transient SH-wave in surrounding rocks has been obtained. The location which may be damaged under the effects of transient SH-wave is found. This place should be reinforced.