| Under the background of the implementation of the “One Belt and One Road” initiative,a series of projects have been accelerated.However,due to the complex engineering environment,various engineering diseases are also increasing.Among them,the diseases caused by the change of water content in the engineering soil and the migration of moisture are not only a few,and more and more attention has been paid to it.Therefore,it is particularly important to monitor the change of soil water content in real time.In addition,with the acceleration of urbanization in China,people have put forward higher requirements for urban land seepage and drainage capacity,Under the concept of “The Sponge City”,many new urban green space optimization schemes have been proposed,which also need to monitor the change of urban soil moisture content to evaluate the optimization scheme.Therefore,the design of a sensor which can continuously and real-time monitor the change of soil water content is of great value to the analysis and prevention of Engineering diseases,as well as to the evaluation and improvement of soil water absorption capacity.In order to meet the requirement of water content measurement in many engineering construction and related experimental research,based on the principle of van der Pauw method,this paper designed a soil moisture content measurement sensor.The final shape of the probe was determined by indoor test and software simulation,and experiments were carried out to study the influence of soil and other factors on the sensor test results.Finally,a model test based on the construction of “The Sponge City” was designed to verify the practicability and accuracy of the sensor.The main contents and research results of this paper are as follows:(1)Based on the principle of van der Pauw method,a set of soil moisture measurement system including AC constant current source,voltage acquisition instrument and calculation program and the four-probe probe were designed.(2)Laboratory experiments were carried out to study the influence of probe spacing and probe length on the resistivity measurement results of probe sensors.According to the requirement of miniaturization of the sensor and the influence of the sensitive factors of the probe on the test results,the final shape of the probe sensor was determined.(3)Using COMSOL simulation software,the potential distribution cloud of soil is drawn,and the internal causes of the influence of probe length and spacing on the test results are analyzed from the point of potential distribution.At the same time,the software calculation results are compared with the probe test results to verify the accuracy of the sensor resistivity test.In addition,the application scope of the improved vdP in soil resistivity measurement is analyzed by COMSOL software,and the improved formula for the application of probe sensor in semi-infinite soil is put forward.(4)Experiments were carried out to study the influence of different soil properties,dry density and temperature on the test results of sensors,and the calibration relationship between soil resistivity and water content was put forward.The accuracy of the sensor was analyzed by comparing the test results of soil moisture content with the drying method,and the test performance of the sensor was evaluated comprehensively.(5)A small model test was designed to verify the applicability,flexibility and accuracy of the sensor in soil moisture measurement,At the same time,the influence of adding seepage wells to urban green space on soil seepage performance was analyzed,which provided technical support for the construction of “The Sponge City”.(6)Field in-situ test was carried out to test the application performance of sensors in field soil moisture content measurement,and to provide a strong criterion for the rationality of the application of vdP method in semi-infinite space soil.The application scope of vdP theory in soil resistivity measurement was expanded. |
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