《爆破安全规程》(GB 6722—2014)边坡岩体爆破振动速度安全允许值的理论探讨

开挖爆破诱发的地震波对岩质边坡有显著影响,我国《爆破安全规程》(GB 6722—2014)给出了边坡岩体的爆破振动速度允许值,但未明确说明取值的理论依据。为此,分析露天开挖爆破条件下邻近边坡岩体的附加动应力和质点振动速度场分布特征,推导以坡表质点振动速度表征的岩体附加动应力表达式。以边坡岩体不发生剪切和张拉破坏为控制要求,考虑边坡岩体分级特征和坡体结构特征,提出基于简单边坡模型的浅层岩体的爆破振动速度允许值。分析表明,岩体强度、边坡坡度、滑动面深度和地震波频率等均对边坡岩体的允许振动速度存在显著影响。其次,无剪切破坏条件下计算的爆破振动速度允许值与《爆破安全规程》(GB 6722—2014)的控制标准在量级上较接近,而无张拉破坏时各级岩体的爆破振动速度允许值差别不大,《爆破安全规程》(GB 6722—2014)中岩质边坡爆破振动控制标准应在理论分析和工程实践基础上进一步细化。

Discussion on the safety threshold of blasting vibration velocity for slope rock masses in safety regulations for blasting(GB 6722—2014)

Seismic waves induced by blasting influence the rock masses of slopes significantly. The national safety regulations for blasting (GB 6722—2014) specifies the permissible value of the blasting vibration velocity of the slope rock，but the theoretical basis of the value is not clearly stated. The dynamic stress and the vibration velocity field in rock slopes induced by blasting seismic wave were analyzed，and the mathematical relationship between the dynamic stress and vibration velocity of rock mass was proposed. To insure that the shear and tensile failures do not take place in rock masses，the threshold of the blasting vibration velocity of the slope surface was proposed based on the simplified slope model considering the classification characteristics of the slope rock and the slope structure. The strength of rock mass，the dip angle of slope，the depth of sliding surface and the frequency of seismic wave all have a significant effect on the threshold vibration velocity. The range of the allowable blasting vibration velocity of different classes of rock mass is proposed according to the mechanism of shallow landslide. The calculated threshold of the blasting vibration velocity under the condition of no shear failure is close to the control criteria of the safety regulations for blasting (GB 6722—2014). The threshold of the blasting vibration velocity of different classes of rock mass is similar to each other when there is no tensile failure. The safety threshold of blasting vibration velocity for rock slopes in safety regulations for blasting (GB 6722—2014) should be refined further on the basis of theoretical analysis and engineering practice.