Simulation Monitoring Of Underground Water Pipe Leakage Based On "Optical-electricity" Comprehensive Testing Technology

In the construction of underground water transmission network,water pipe leakage caused by aging and damage of water pipe occurs from time to time.The leakage of buried water pipes not only leads to a large waste of water resources,but also causes geological disasters such as ground collapse and cavity,which seriously threatens the safety of people’s lives and property.Therefore,it is important to adopt real-time and accurate water pipe leakage monitoring methods for monitoring and early warning of buried water pipe leakage.Taking the soil around the water pipe as the research object,this paper proposes a comprehensive test method combining optical fiber and parallel electrical method(hereinafter referred to as "Optical-Electricity" comprehensive test method).Calibration experiments and physical simulation tests were carried out,and 47 groups of effective electrode current data,47 groups of spontaneous potential data and 141 groups of temperature characteristic value data were collected.The response characteristics of physical parameters in the process of water pipe leakage were studied,and the location of leakage points and the extent of leakage were determined by monitoring.The specific research results are as follows:(1)The Logistis mathematical model between temperature characteristic value and moisture content is established.Through the design of water content calibration experiment,the response characteristics of each parameter with the change of water content are as follows: the characteristic value of temperature decreases successively in air,dry soil and water bearing soil,and decreases with the increase of soil water content;The excitation current increases with the increase of soil moisture content;The spontaneous potential value tends to be stable after changing with the increase of soil moisture content.(2)The monitoring conditions of the sensor with high precision and high stability are optimized.The experimental results show that under the condition of30 V heating voltage,the recognition accuracy of AHFO-FBG sensor for soil moisture content is better than 15 V heating voltage,and the change of temperature characteristic value is more obvious;When the sand ratio is 9:1,the soil with different moisture content has better uniformity and more sensitive parameter response.(3)The indoor physical model test based on "Optical-Electricity" comprehensive test technology is constructed.The test results show that when the soil moisture content near the monitoring point increases,the temperature characteristic value decreases and the excitation current increases,the spontaneous potential value first increased as a whole,then decreased slightly and tended to be stable,and the strain optical fiber compressive strain increases significantly;Combined with the calibration function relationship,the change process of soil moisture content is quantified,and the location and scope of leakage port are identified.(4)The lateral and longitudinal moisture content distribution nephogram and the response sensitivity between parameters during the leakage process are analyzed.It is further determined that there is a negative correlation between the response characteristics of temperature characteristic value and electrode current value in the process of pipeline leakage: when the soil moisture content is less than 11%,the sensitivity of temperature characteristic value to the change of moisture content is higher than that of current value;On the contrary,the sensitivity of temperature characteristic value to moisture content change is lower than that of current value.Figure [64] table [4] reference [112]...