With the invitation of Survey and Design Institute of Hydraulic and Electric in Shangrao City of JiangXi Province, Beijing Orangelamp geophysical Prospecting Co., Ltd. sent out staffs to detect the dams of Reservoir in PoYang County using GDP-32 II multi-function electric system by American Zonge company producing. On Jan. 7, in 2011 we went into the site, then on January 8 and January 9 we worked in the field construction. And in the night of January 9, in 2011 we left the site. This survey we used NanoTEM in the instrument of GDP-32 II to work by the device of the center loop.
A. the parameters of the instrument and live field work as follows:1.the receiver of GDP-32II(as fig.1)
main parameters
dc resistivity;
time-domain and frequency-domain IP method;
complex resistivity method;
Controlled Source Audio-Frequency Magnetotelluric sounding;
frequency domain electromagnetic method;
transient electromagnetic method;
Nano transient electromagnetic method;
side:43*41*23cm
weight: big box 20.5kg small box 13.7kg
Fig.1 the receiver of GDP-32II
2.the NT-20 receiver of NanoTEM
main parameters:
input voltage: from 12 to 36 voltage
output way: 50 percent and 100 percent
maximum output current:3.5A or 20A
cutoff time: 1.5us
side:22*28*18cm
weight:5kg
Fig.2 the receiver of NT-20
3. Field construction site( in fig.3)
Fig.3 Field construction site
B. The field construction and detective result in JunMin reservoir
1. The brief of the field construction
1) On January 8, on the basis of the research we made sure devices in the field and set parameters, and in the top of the dam we used the device of center loop, and we carried on detecting with 7 meters in side of the transmitting coil and 2 meters in distance between two points. Test results (in figure 4).
Figure 4 on January 8, in the top of the dam the detective profile section of the resistivity of the inversion 2 meters in distance between two adjacent points
In the figure 4, from 74th to 78th points, from 93rd to 97th points, from 140th to 144th points, from 180th to 184th points, from 225th to 229th points, from 255th to 260th points, from 280th to 284th points, from 355th to 360th points, from 368th to 373rd and from 392nd to 415th points totally 10 points, the elevation of 70 meters up and down there were the anomalies of the low resistivity in part. In addition, under the elevation of 65 meters had largely the anomalies of the low resistivity, and this negative resistivity repeatedly appeared, but these anomalies were often the insufficient densities, caused by the interpolation of the grid process.
2）on January 9, in the top of the dam we used the device of center loop, and we again carried on detecting with 5 meters in side of the transmitting coil and one meters in distance between two points. Test results (in figure 5).
Figure 5 on January 9, in the top of the dam the detective profile section of the resistivity of the inversion 1 meter in distance between two adjacent points
In the figure 5th, 7th、140th、227th、286th、357th、370th and 410th points totally 7 points, the elevation of 80 meters up and down there were the anomalies of the low resistivity in part. 75th、140th、186th、225th、283rd、358th、373rd、395th、410th and 430th points totally 10 points, the elevation of 70 meters up and down there were the anomalies of the low resistivity in part. 65th、100th、140th、165th、180th、250th、284th、305th、333rd、and 355th points totally 10 points, the elevation of 65 meters up and down there were the anomalies of the low resistivity in part.
As figure 6 showed among the contrastive result twice, and 75th、100th、140th、165th、186th、225th、255th、280th、235th、355th、373rd、395th and 415th points totally 12 points had better recreating and corresponding.
In figure 6 the contrastive result of on January 8 and January 9
On January 8 and 9, the top of the testing results showed that in 75th、100th、140th、165th、186th、225th、255th、280th、235th、355th、373rd、395th and 415th points totally 12 points, and the impermeable wall existed in joint seam where maybe twice impregnated mud before and after or the consolidation of alkali body became problems in the underpart of the wall. In addition, deep anomalies should caused by drainage hole in 353rd point.
In addition, in 137th and 340th points across the dam we carried on two test section with 5 meters in side of the transmitting coil. Test results (in figure 7).
In figure 7 the figure of test results in the cross section of the dam about 137th points (left figure)
In figure 7 the figure of test results in the cross section of the dam about 137th points (right figure)
Figure 7 in the left according to the anomalous electric resistivity, at the cross section of 137th points where existed in the weak anomalies of the low resistance from 64 to 66 meters of the elevation in the left of the impermeable wall and where existed in the strong anomalies of the low resistance from 54 to 58 meters of the elevation in the right of the impermeable wall, so the former showed that the wall must exist in some problem, but because of the upper impermeable wall seeping the latter maybe caused by water content heightening in part.
According to the contrast of test results in the cross section of 137th point and 340th point, we obtained that 137th point of the dam had relatively strong soil and on the right of the dam 340th points had relatively weak soil below the elevation of 50 meters.
the conclusion
In reservoir the detective effect was remarkable by using of NanoTEM of GDP-32 II.
In reservoir the detective result indicated that the overall quality of diaphragm wall of the dam was good, only existed in problem in joint seam of the impermeable wall. Especially from 135th to 145th points when necessary considered reinforcement. In 340th point there was relatively weak soil at the bottom of the dam, what should be valued, because it influenced the reliable degree of the dam.
