工业爆破的地震效应

一、前言在固体介貭中爆炸时,一部分能量轉化为弹性波,对地层和建筑物产生与地震波相似的影响。工业爆破常需在厂矿区、建設工地或居民点附近进行。为了确保安全,有必要研究其地震效应。

SEISMIC EFFECT OF CONSTRUCTION BLASTING

During the years 1956 to 1960,we studied instrumentally and macroseismically the seismic effect of a series of blastings in six different regions,with explosive charges ranging in size from 50 gin. to 1,371 tons. The instruments used consisted mainly of two kinds of electrodynamic displacementmeters: one operated in the range of lμ to 1mm.,while the other 1mm. to more than 10cms. When used to record ground vibrations with periods from 0.02 to 0.5 sec.,the estimated error in displacement was not more than 10％. Field experience showed that these instruments are easy to handle and stable in characteristics. In the vibrating zone,the main phase,in which the energy of seismic waves concentrated,usually had frequencies between a few c.p.s,to more than ten c.p.s. This is the range of frequencies of structural interest,and is believed to be the most destructive to buildings. The following emperical relations were found in a joint analysis of instrumental data and macroseismic phenomena: 1. The relation between the vertical component of maximum velocity of ground motion V_,in cm./sec.,and charge size C,in kg.,and distance R,in meters,can be expressed by the formula: lg V_=K+0.6lg C-1.8lg R,where K is a parameter ranging from 2.2 to 2.6,with a mean value of 2.4 on normal overbunden for ordinary conditions of blasting. 2. When V_approaches 10—15 cm./sec.,light injury may occur in ordinary singlestory buildings; when V_is greater than about 30 cm./sec.,many buildings suffer damage; when V_surpasses 60—70 cm./sec.,destruction to buildings is serious,and fissures sometimes occur in the bed rock. 3. The seismic effect of blasting designed for directional blowout of overburden,also showed non-uniformity in different directions. Ordinarily,the strength of vibration had a tendency to increase with the depth of center of explosion below ground surface. Under certain conditions,topographic relief and faulting may also influence the strength of vibration.