岩土层受力时电阻率变化与应变的关系

THE RELATIONSHIP BETWEEN RESISTIVITY VARIATION AND STRAIN IN A LOAD-BEARING ROCK-SOIL LAYER

与基线测量和电阻应变片测量资料对比,得到小应变条件下某些天然不饱和岩、土层电阻率对应变的比例(放大)系数K=△ρ/ρ/△ε可达10~3,且应变愈小K值愈高.分析这种实验结果得到,电阻率ρ与应变ε的关系为ρ∝φ^(-(E+F_ε^(0.4)),其中φ为孔隙度;E,F为常数.这说明,受力时岩石的结构指数n不再是通常认为的常量,而是应变的函数,即n=E+F_ε^(0.4).所以高放大系数是不饱和岩土层在微小应变条件下的一种较普遍的规律.选择放大系数不低于10~3的台址,进行电阻率观测,可望在地震前震中附近观测到5％量级的异常变化。

It is obtained from a comparison of the data from base line measurement and resistivity strain gauge that first,the ratio of resistivity to strain,i.e.,the (hagni-fication) factor for small strain in some naturally unsaturated rock-soil layer is relatively high with a maximum of 103,and second,the smaller the strain is,the higher the magnification factor k will be. The relationship between resistivity p and strain e has been found from an analysis of the second fact as where is the porosity,E,F are constants. This shows that the structural coefficient ?is no longer a constant as thought previously. It is in fact a function of strain,i.e.n= E+Fε. Therefore,the high magnification factor is thought as a generally accepted law concerning the unsaturated rock-soil layer under small strain rather than a particular feature of rocks. It is pointed out that an observation location with a magnification factor of no less than 105 could be chosen for resistivity measurements so that an anomaly of 5% will hopefully be observed near the epicentre before an earthquake.