爆破荷载作用下空洞效应对围岩振动速度的影响

以某高速公路工程的隧道工程为依托,针对隧道爆破施工中空洞效应对围岩振动速度的影响问题,根据能量法和地震波传播规律推导出爆破荷载作用下已开挖区和未开挖区围岩振动速度计算公式,采用有限差分软件模拟不同荷载作用下围岩振动速度的变化规律,并验证了计算公式的准确性。结果表明,空洞效应下的围岩振动速度数值模拟计算结果和计算公式求解结果误差在6%以内; 爆破荷载0.8 MPa作用下,空洞效应影响较大的区域位于距掌子面8~12 m处的隧道拱顶处,距掌子面8 m处的开挖区与未开挖区隧道拱顶处的振动速度差值为2.23 cm/s,商值为1.21倍; 在一定荷载范围内,荷载越大,空洞效应对围岩振动速度影响越明显,已开挖区与未开挖区振动速度差值的峰值距掌子面越远。

Influence of Cavity Effect on Vibration Velocity of Surrounding Rock Under Blasting Load

With the tunnel engineering of an expressway project as an example, aiming at the problem that the cavity effect during tunnel construction by blasting brings an impact to the vibration velocity of tunnel surrounding rock, the calculation formulas for the vibration velocity of surrounding rock in the excavated area and unexcavated area under blasting load were derived according to the energy method and the propagation law of seismic wave. The variation law of vibration velocity under different loads was then simulated by using the finite difference software, and the accuracy of the calculation formula was also verified. The results show that the error between the results of numerical simulation and that from the formula is less than 6%. When the blasting load is 0.8 MPa, the area with larger cavity effect is located at the crown of the tunnel from 8 m to 12 m away from the working face. There is 2.23 cm/s difference in the vibration velocity at the crown of the tunnel between the excavated and unexcavated area that is 8 m away from the working face, with the quotient value of 1.21 times. Under a certain range of load, the larger load can result in more obvious impact on the vibration velocity of surrounding rock by the cavity effect, and also lead to the peak value of difference in the vibration velocity between the excavated area and non-excavated area farther away from the working face.