Three-dimensional Finite Element Analysis Of The Fitted Flow Field Method For Detecting Dam Leakage

Levee engineering is an important component of flood prevention,and also an important safety barrier against flood.In our country,levees engineering have been built to 331,000 kilometers in length,but only 74.9% of the levee project is qualified.In other words,there are still 25.1% of levee projects have various hidden dangers,seriously threatening the safety of people’s lives and property.During the "14th Five-Year Plan" period,the state plans to invest100 billion yuan to control the sick reservoir.Piping leakage are one of the most serious hidden diseases of dikes.So,how to detect the piping leakage area is an important prerequisite for controlling hidden dangers of dikes.The flow field fitting method is to place electrodes on the leakage outlet of the back slope of the dam and on the facing water body of the dam respectively to combine and strengthen the abnormal part of the water flow field.It measures the current field to achieve the effect of measuring the water flow field,and it can quickly and accurately detect the location of piping leakage inlet.And also is one of the main methods to detect the hidden danger of dam leakage.However,some problems may be encountered in the actual detection the hidden danger of dam leakage.Firstly,the point current source cannot be accurately placed at the leakage outlet because the leakage outlet area is concealed or people can’t approach.Secondly,it is easy to rotate the sensor when the boat is towing it because the sensor is measured where close to the water bottom.To solve these problems,the model that point current source is far away from the leaky outlet area of the levee is analyzed with use the three dimensional finite element method of unstructured mesh finite element.Estimate the abnormal characteristics by calculating the potential and current density response.It is found that when the point source is perpendicular to the dam and far away from the leakage outlet,the abnormal response patterns of the components of potential and current density do not change much,but the values become smaller.It has hardly effect on the detection of leakage hazards.Oppositely,when the point source is parallel to the dike and far away from the leakage outlet,the abnormal response of each component of the potential and current density changes not only in value,but also in form,which may affect the actual hidden trouble detection of the levee engineering.Simulation analysis of sensor to solve the spin problem.It is found that when the sensor rotates,the shape of each component of the current density changes.It will make it difficult to interpret the actual data and even lead to misjudgment of the abnormal area of leakage.Therefore,propose install the attitude recorder on the sensor to record the rotation Angle,and then the rotation correction formula is used to correct the deviation caused by the rotation of the sensor,which provides a new idea for some problems encountered in the detection of potential seepage problems by flow field fitting method.