Study And Application Of Full Space Transient Electromagnetic Response Characteristics Of Concealed Water Source With Low Resistance Coverage

When the transient electromagnetic method is explored in the area covered with low resistance layer,the low resistance shielding effect will affect the exploration depth of the transient electromagnetic method,which leads to the decrease of signal to noise ratio of the late data.Therefore,in this paper,the transient electromagnetic response characteristics of the subsided column under the condition of low resistance shielding under the condition of full space are studied in two aspects of numerical simulation and physical simulation.Under the condition of full space,the numerical simulation of the target body(water cut column)covered by the low resistance layer is carried out to study the transient electromagnetic response characteristics of the hidden disaster water source(water cut column)affected by the low resistance shielding.In the numerical simulation,the distance between the coil and the low resistance layer,the size and the depth of the target body are changed respectively.The characteristics of the transient electromagnetic response of the target body are studied at this time,and the law of the delay effect caused by the low resistance shielding is summed up by the previous numerical simulation,and the physical simulation is carried out under the full space condition according to the content of the numerical simulation.By comparing the experimental data with the response characteristics obtained by numerical simulation,it is found that the above is a single peak abnormal curve shape.The size of the copper rod affects the curve extremum,the increase of the distance between the coil and the aluminum plate makes the shape of the curve slow,and the change of the distance between the copper rod and the aluminum plate does not have a significant effect on the shape and even the extreme value of the curve.Due to the influence of low resistance shielding,when the transient electromagnetic method has low resistivity layer in the depth of detection,it can hardly observe the response characteristics of the deep low resistance body on the induction potential profile.It can only determine whether there may be a collapse column under the low resistance layer according to the response characteristics,and it can not confirm its position.The detectable potential curves of the side can find the anomaly caused by the aluminum plate,and can reflect the existence of the copper bar in the curve and correspond to its location.Effect of copper size on response characteristics can come out in the induction potential of a very good response curve.When the transient electromagnetic method is parallel to the low resistance layer in the side of the low resistivity layer,the response characteristics of the deep low resistance body can be observed on the induction potential profile,and the possible existence of the collapse column under the low resistance layer and its position can be confirmed according to the response characteristics.