Study On Calculation Method Of Dynamic Stress Of Earthrock Dam With Polymer Anti-seepage Wall Under Earthquake Load

At present,as a new type of light-weight anti-seepage wall,the anti-seepage reinforcement performance of the polymer anti-seepage wall has been widely recognized.Compared with other types of anti-seepage walls,the polymer anti-seepage wall has many advantages such as environmental protection,light weight,high expansion rate,fast strength improvement,strong anti-seepage ability,good durability and excellent mechanical properties.However,the existing researches mostly focus on the grouting technology,material properties,and anti-seepage effect of the polymer anti-seepage wall.The research on the seismic performance of the polymer antiseepage wall is relatively scarce,which limits the popularization and application of the polymer anti-seepage wall in seismic areas.Therefore,it is particularly important to study the seismic performance of the polymer anti-seepage wall.Dynamic stress is an important index to measure the seismic performance of anti-seepage walls.When calculating dynamic stress with conventional finite element method,it is necessary to derive displacement,which results in lower calculation accuracy and is not conducive to seismic safety evaluation of structures.In this paper,the minimum complementary energy method for dynamic stress calculation is theoretically deduced and programmed,the numerical calculation is carried out according to the results of finite element analysis,and the dynamic test results are used to verify and evaluate.The research on the dynamic response law and the accurate dynamic stress calculation method of the polymer anti-seepage wall are carried out by combining the above three methods,mainly including the following four aspects:(1)A secondary analysis method combining the minimum complementary energy method with finite element method is proposed to calculate the dynamic stress of antiseepage walls.The minimum complementary energy calculation process of dynamic stress of three-dimensional isoparametric element with 20 nodes is derived and the corresponding Mathematica dynamic stress calculation program is developed.(2)Dynamic finite element models of earth-rock dam with the polymer antiseepage wall and earth-rock dam with the plastic concrete anti-seepage wall are established and analyzed,and dynamic response laws of the two types of anti-seepage walls under four seismic conditions are summarized.It is found that the maximum tensile stress and maximum compressive stress of the polymer anti-seepage wall are much lower than that of the plastic concrete anti-seepage wall under the same working conditions due to its light weight,small elastic modulus and good deformation coordination,and it has a high safety reserve.So the polymer anti-seepage wall is not prone to tensile and compressive damage.But the plastic concrete anti-seepage wall has a big weight,low tensile strength and excessive dynamic stress in the middle and lower parts,which is prone to tensile and compressive damage.It shows that the seismic performance of the polymer anti-seepage wall is better than that of the plastic concrete anti-seepage wall.(3)Based on the results of finite element numerical simulation,the minimum complementary energy method is used to calculate dynamic stress of anti-seepage walls,and compare it with the conventional finite element method of dynamic stress.It is found that the time-history response law of dynamic stress of the two methods is basically the same.The minimum complementary energy method of the maximum dynamic stress is generally larger than that of conventional finite element method,and the increase of dynamic stress is within 30%.The correctness of the dynamic stress calculation program of the minimum complementary energy method is verified,and it is shown that there is a difference between the minimum complementary energy method and the conventional finite element method in the dynamic stress calculation accuracy.(4)Centrifuge shaking table tests on two types of earth-rock dams with antiseepage walls are carried out,and the finite element analysis results of dynamic stress and the calculation results of the minimum complementary energy method are evaluated.It is found that the maximum dynamic stress distribution law along the wall height in model test is basically in accordance with the law of numerical analysis.And the minimum complementary energy method of maximum dynamic stress of the two types of anti-seepage walls is closer to the test result than the conventional finite element method.After the test,the integrity of polymer anti-seepage wall is good but obvious penetrating cracks appear in the middle and lower part of the plastic concrete anti-seepage wall.The test results prove the correctness of the numerical analysis results,and verify the correctness and effectiveness of the minimum complementary energy method for improving the calculation accuracy of dynamic stress of the polymer anti-seepage wall in earth-rock dams.