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在野外原地对某些自然状态非饱和的土层及含裂隙矽化灰岩电阻率随应变的变化进行了实验.主要结果有:1)低应力下,随体积的压缩电阻率下降;体积膨胀时电阻率上升;2)所测岩、土层电阻率相对变化(Δρ/ρ)对微小应变(δ)的变化响应甚为敏感,裂隙岩层比土层更甚.放大系数(Δρ/ρ)/ε与应变量有关,对10~(-4)应变通常有一、二百倍,对10~(-5)应变可达数百乃至上千倍;3)电阻率相对变化幅度随力源强度和尺度的增加而增加,随力源距离的增加而衰减.电阻率变化起始时间随距离的增加显示出滞后现象;4)水平各向同性土层,在应力作用下,不同方向电阻率变化不同,呈现出方向性.通常垂直最大压缩方向的电阻率ρ_L 下降较多,平行方向的(?)下降较小或略有上升,与压力呈45°的ρ_(45°)下降幅度介于中等.含裂隙矽化灰岩则不同,不同方向电阻率的变化不仅与压缩方向有关,而且还与裂隙方向有关.通常是ρ_(11)下降较多.当压应力平行裂隙时,ρ_L 也下降,但当压应力垂直裂隙时,ρ_L 则明显上升.
In the field, the resistivity of some naturally unsaturated soils and fractured silicified limestones were experimentally changed in situ with the following results: 1) The compressive resistivity decreases with volume under low stress; the volume expansion (Δρ / ρ) is sensitive to the change of small strain (δ), and the fractured rock formation is more serious than the soil layer. The magnification factor (Δρ / ρ) / ε is related to the amount of strain, and usually has one or two hundred times the strain of 10 ~ (-4) and several hundred or even thousands of times of strain of 10 ~ (-5); 3) The relative change of resistivity varies with the strength of the source And the scale increases, and decays with the increase of the distance of the power source.The initial time of resistivity change shows the hysteresis with the increase of the distance.4) In the horizontal isotropic soil, the resistivity changes in different directions under the stress The resistivity ρ_L of the direction of the maximum vertical compression decreases more, the decrease of the? In the parallel direction decreases slightly or slightly, and the decrease of ρ_ (45 °) at 45 ° from the pressure decreases moderately Unlike fractured silicified limestone, the change of resistivity in different directions is not only related to the direction of compression, but also For fracture direction is generally ρ_ (11) decrease more. When stress cracks parallel, ρ_L also decreases, but when the vertical stress fracture, ρ_L significantly increased.