爆破荷载作用下隧道围岩裂隙范围计算方法研究

A study of fracture range of tunnel surrounding rock under blasting

爆破荷载下隧道围岩产生的裂隙为岩溶发育和地下水运动创造了良好的条件。为了研究爆破荷载作用下隧道围岩的损伤裂隙范围,在考虑中主应力和环向拉应力的影响下,分别基于统一强度准则和摩尔库伦强度准则得到了两种粉碎区的计算方法,并且计算了破裂Ⅰ区和破裂Ⅱ区的范围。最后开展了现场试验和探测,按本文计算方法计算了现场隧道粉碎区和裂隙区范围,计算结果与现场试验结果进行了对比和验证,得到了以下结论:①本文基于统一强度理论的粉碎区范围计算方法考虑了塑性损伤,适用于隧道粉碎区范围的计算,理论计算结果与现场粉碎区实测结果较为吻合,该方法可用于超欠挖控制严格的隧道爆破参数设计;②本文基于摩尔库伦强度准则的粉碎区范围计算方法不考虑塑性损伤,相比已有的基于摩尔库伦强度准则的计算方法考虑了环向拉应力,计算单元体更符合实际受力情况,本文粉碎区的两种计算方法主要区别在于是否包含塑性损伤的范围,两种计算方法在实际运用时,应根据不同的工程要求来选择;③现场试验结果表明,基于统一强度理论的破裂区范围的计算方法,其计算结果与现场实测结果较为接近,该方法可以用来计算和评估远场振动效应作用下隧道围岩的裂隙范围。

The fractures of tunnel surrounding rock under blasting load provides good conditions for karst development and groundwater movement.In order to study the fracture range of surrounding rocks under blasting load,considering the influence of medium principal stress and circumferential tensile stress,two kinds of calculation models of crushing area were obtained based on unified strength criterion and Mohr Coulomb strength criterion,respectively.When the crushing area was filled with blasting gas,the secondary expansion range of fracture was calculated.Then,the scope of crushing area and fracture area was calculated through an engineering example,and the calculation results were compared and verified with the site experiment results.Finally,the following conclusions were obtained.①The calculation method of crushing area based on the unified strength theory considers plastic damage,which is suitable for the calculation of tunnel crushing area.The theoretical calculation results are in good agreement with the site experiments results.This method can be used to design blasting parameters of tunnels with strict control of over excavation and under excavation.②The calculation method of crushing area based on the Mohr Coulomb strength criterion does not consider plastic damage.Compared with the existing calculation methods based on the Mohr Coulomb strength criterion,the circumferential tensile stress was considered,and the calculation unit body is more in line with the actual stress situation.The main difference between the two calculation methods of crushing area in this paper is whether the range of plastic damage is included.The two calculation methods should be selected according to different engineering requirements in practical application.③The site experiment results show that the calculation results of the fracture zone range based on the unified strength theory are close to the site experiments results,and this method can be used to calculate the fracture range of tunnel surrounding rock under similar blasting action.