Study On Stiffness Testing Technology Of Geocell Reinforced Cushion And Its Calculation Theory

Geocell reinforced cushion in the composite foundation reinforced in two-direction serves as a flexible raft foundation, to spread and homogenize the upper load, restrain lateral deformation of ground, effectively regulate the pile-soil stress sharing and so on. Further theoretical studies have shown that the exerting of above function of geocell reinforced cushion has a close contact with bending rigidity. However, there is a significant unreasonable in current theoretical analysis in which the deformation modulus of geocell cushion is taken to compute bending rigidity. To this end, a method that test bending stiffness of geocell cushion by using stacked beam system is put forward in this thesis.In order to obtain its test method and calculation theory, firstly contact law of laminated beam was studied in the thesis. The contact problem of laminated beam is formed as linear complementarity problem to overcome irrational results from traditional analytical solution, and the general solving process based on the lemke algorithm is established. On the basis, the contact law of stacked beam under typical load is studied.Secondly, a finite element analysis based on commercial finite element software ADINA is carried out, to further understand mechanical properties of stacked beam. On the one hand, the contact law of stacked cantilever beam with various load type and stiffness ratio is studied. On the other hand, on stress and strain of simply supported beam under two common loadings is studied, considering the effect of stiffness and friction.Then the stiffness of geocell reinforced cushion is tested. Firstly some ordinary stacked beam tests is carried out, and based on that, a group of tests that testing geocell cushion's stiffness is completed. Factors, such as geocell specifications, filler type and packing density, have been taken into consideration in the test.According to these tests, an improved method to calculate geocell cushion stiffness is put forward in this thesis. By comparing calculated values and existing test results from ordinary beam tests, it is found that the calculation accuracy has improved significantly from traditional methods. Then, geocell cushion stiffness tests are calculated, and a statistical analysis of results are carried out too.Finally, some conclusions are drawn as follows. Bending elasticity modulus of large-sized geocell cushion with gravel are from 50 to 100MPa, the average is about 70MPa; Bending elasticity modulus of large-sized geocell cushion with silt materials are from 40 to 80MPa, the average is about 60MPa; Bending elasticity modulus of small specifications geocell cushion with gravel are from 35 to 55MPa, the average is about 45MPa. Thus, from this thesis, the basis for evaluating bending rigidity parameters of Geocell reinforced cushion is provided, and the test content of macro material mechanics parameters is enriched.