The Key Technology Of TEM-MRS For Groundwater Detection

MRS(Magnetic Resonance Sounding)is currently the only type of trenchless detection methods of groundwater exploration, this method has advantages such as obtaining information comprehensive,unique explanation, result quantization, low cost , has achieved very good application results. But the method of MRS also has shortcomings: the probing depth limited, the probing resolution ratio is lower, measurement speed is slow, the ability of anti-interference is relatively poor etc; TEM (transient electromagnetic method) just can remedy these defects, but as an indirect method of groundwater exploration TEM has its inherent disadvantages: the measurement data has multi-solutions, the result can't quantization, unable to access the hydrogeology information needed in digging a well. In this paper, we combined TEM with MRS forming a new method of TEM-MRS combined to groundwater exploration (for short: TEM-MRS combined method). The new method of TEM-MRS combined to groundwater exploration makes TEM and MRS have complementary advantages and improve detecting speed and efficiency together. In addition, due to the similarity of TEM instrument and MRS instrument systems in principle, component and structure, this paper proceed the job of integrated design and research of the instrumentation systems of TEM-MRS combined to groundwater exploration.(for short: TEM-MRS combined instruments).This paper is accomplished under the common funded by special topic project of National"11th five-year"plan projects"research and development of Scientific instruments and equipment", project of ministry of Education, project of Palace of Science in Jilin province.The mainly technology and results in this paper are as follows:(1) Carried out the theory research work in groundwater probing by using MRS and TEM combined technique and improved quantitative interpretation depth of combined detecting. Given TEM-MRS for groundwater detective methods of different types of groundwater, studied the combined interpretative method of TEM-MRS for groundwater detective results, using this interpretation can eliminate multiple solutions and no quantitative of TEM measuring result, which made one-dimensional quantitative interpretation depth of combined groundwater detection reach -300 meters.(2) Carried out design and research work of the integration of combined system. Based on JLMRS-I nuclear magnetic resonance groundwater exploration instrument system and ATEM-II transient electromagnetic instrument system, designed and researched TEM-MRS groundwater detection instrumentation system. This instrument is currently the only integration of TEM-MRS combined groundwater detection instrumentation system, with deep detecting depth, high resolution, fast measuring speed unique interpretation, result quantification ,etc.(3) Carried out research of correlation technique to improve detecting efficiency of the instrument. Mainly studied fast charging technology, multi-mode separation coil receiving and dispatching technology, low noise and greatly dynamic changes the sampling rate signal gathering technology, bandwidth multiplexing multi-port serial communication technology, etc, these technologies improved detection efficiency of MRS-TEM by increasing running speed, decreasing run time, reducing number of superposition etc.(4) Carried out research of correlation technique to improve detecting range and resolution of this instrument. Mainly studied the method of combined interpretation, energy-storage excitation techniques with large capacity and high resolution, small coil receiving technology in multi-mode separation coil receiving and dispatching technology. These methods and technologies can enlarge detecting resolution of TEM-MRS in horizontal and vertical.(5) Carried out research of correlation technique to improve anti-interference capability of this instrument. Mainly studied low rectangular coefficient narrowband filter technology, reference de-noising technology and relay smooth transition of"one transmit two receive". These technologies ameliorated the signal-to-noise ratio of received signal by improving the anti-interference ability of TEM-MRS combined instrument.(6) Carried out the field contrast test and actual application of this instrument. Introduced the choice of the field that used as contrast test, given the consistent contrast experiment results of TEM-MRS combined instrument worked in the contrast test field, given transverse comparison test results between TEM-MRS and NUMISplus and results between TEM-MRS and ATEM-II, given contrastive results between TEM-MRS and actual drilling results. Introduced the application of TEM-MRS combined instrument in the project of prospecting drinking water sources at Erenhot of Inner Mongolia and the applied situation for drought resisting in southwest.The main innovation points of the paper are as follows:(1) Studied the ways of the TEM-MRS for groundwater detecting in different groundwater. Put forward combined interpretative ways of TEM-MRS for groundwater detecting result, which made one-dimensional quantitative interpretation depth of TEM-MRS for groundwater detecting reach -300 meters. The combined interpretative method established the relationship between water content and resistivity by using the measured results overlaps of TEM and MRS, we reversed applied this relationship to explain resistivity distribution achieved from TEM measured results to eliminate multi-solutions and no quantitative of TEM measure.(2) Developed the integration of TEM-MRS combined groundwater detection instrumentation system. Based on the comparability of MRS and TEM at system architecture and operational principle etc, this paper studied the correlative technology of incorporate combined instrument system, with the basic design thought of realizing the resource share and modularity realization as far as possible, finally designed and developed the research-prototype of TEM-MRS groundwater testing system, and has adopted the project acceptance of MOST. This instrument supplied a gap for the field of incorporate TEM-MRS combined instrument system.(3) Put forward the method of quickly smooth transition to restrain the switching interference of relay and studied the correlation technique. In this paper we have presented a way to eliminate interference when the relay switching by adding a parallel controlled absorbing circuit between relay and signal disposal circuit; studied a technique to realize relay fast smooth transition, relay switching time shorten from 30ms to 8ms by using this technique. Shorten switching time has two main effects: First, ameliorated the signal-to-noise ratio of received signal and improved the anti-interference capability of TEM-MRS. Second, received the MRS-FID signal produced by bound water, which made TEM-MRS combined instrument has the ability of detecting bound water.(4) Put forward the way to improve the longitudinal resolution of MRS measuring by increasing the number of excitation layers and studied correlation techniques. In this paper we presented a method of improving MRS measuring longitudinal detecting resolution through increasing the capacity of reserved capacitance to add the number of excitation layers; studied the technology of power parallel work which can doubled increase MRS measuring no overlap excitation layers, using this technique we can enable multiple power box parallel work, which can doubled increase the capacity of reserved capacitance and no overlap the number of excitation layers under the circumstance of keeping the original charging rate unchanged, so as to improve longitudinal detecting resolution of MRS measure. The improving longitudinal resolution can make TEM-MRS with more broad application prospect.After research of this paper, we designed and developed an integrative TEM-MRS combined instrument, it filled in a gap in the integrative TEM-MRS groundwater detecting instrument. Through the field experiment and practical application, we can see that TEM-MRS has excellent properities, such as low cost, the amount of work is small when working in the field, large detecting depth, high speed of detection, high resolution of detection, strong anti-interference ability, result quantification, unique interpretation etc. It has a good application prospect in many fields like deep groundwater exploration, groundwater resource survey, environmental monitoring, archaeology etc.