Study On Tests And Analysis On Theory Of Coupled Behaviors Of Consolidation And Creep Of Soft Clay

The time's effect of the soil mass's deformation has great effect on the mechanics property of the soil mass. Being compressed, the deformation of the soil mass includes two processes as consolidation and creep that is coupled processes of consolidation-creep.Basing upon the research trends of the home and abroad and the demands of practical engineering, summarizing the predecessors' researches, the thesis studied on tests and analyzed on the theory of coupled character of consolidation and creep of the representative soft clay in Wuhan area. The means of indoor test about consolidation and creep of the soft clay was discussed; the rule of deformation about the coupled character of consolidation and creep of the representative soft clay in Wuhan area was summed up; the empirical formula about deformation of consolidation and creep of the representative soft clay in Wuhan area was fitted out; the pragmatic nonlinear elastic-viscous model about consolidation and creep of the representative soft clay in Wuhan area was established; the finite element equation of the pragmatic model was reasoned out; basing on the TDBC-95 program, the finite element calculator program was reprogrammed with the FORTRAN language; moreover, a project instance was given to verify the theory's and the program's feasibility and applicability.The main conclusion of the original consists of:1 .The coupled character of consolidation and creep may be studied by the directly shear-test unit and style three axes compression unit that be refit by the ordinary strain-control style directly cut-test unit and strain-control style three axes cut-test unit and one-dimension consolidation set. The results of the one-dimension compression tests and the three-dimension consolidation-creep tests with the representative soft clay in Wuhan area show the relationship curves of time and strain have the similarity. When the stress level is lower, attenuation creep arise, the creep finally inclines to a certain stable value the time increasing. When the stress level is higher, non-attenuation creep is able to happen, the more the stress level is high, the more obvious the displacement of creep.2.The experiment research and outcome analysis show, when the stress level is lower, the isochronous relationship curves of the partial stress—strain are approximately some straight lines; When the stress level is higher, they act as one cluster of broken line approximately in these tests of the three-dimension consolidation-creep. When the stresslevel is lower, the isochronous relationship curves of the vertical stress- strain of the one-dimension compressing consolidation-creep are approximately some paracurves. When the stress level is higher, they act as one cluster of right line approximately. Yet the same regular rule that they wholly expressed out is, the isochronous relationship curves of the stress-strain of specimen are one cluster of broken line either right line approximately, the soft clay creep act as nonlinear creep approximately. If the stress level is high over, these curves overstep in the direction of strain axis being near, the creep deformation is obviously over.3.The creep may occur below two kinds of terms of consolidated-drained and consolidated-undrained. Below the stress level action, the specimen's deformation value below term of that drains away water is more than the specimen's deformation value below term consolidated-undrained far away. With the increasing of loading series, the specimen's deformation rate below the term consolidated-undrained is more than to the specimen's deformation rate below the term consolidated-drained one by one, and finally present situation of the specimen's deformation value below the term consolidated-undrained overtake to the specimen's deformation value below the term consolidated-drained. Below the same term of consolidated-drained or consolidated-undrained, the creep of specimen is difference if the water content and load series is difference. Below the same term of the water content, that the creep of specimen happens the alternation with load series and term of consolidated-drained or consolidated-undrained.4.Below the term of consolidated-drained, the water content of specimen is high over; the deformation value of the specimen is great over. Below the term consolidated-undrained, when the low stress level action, the water content of specimen is high over, the deformation of the specimen is great over, Yet the deformation value adds not half the water content getting higher; when higher stress level action, on the contrary the deformation value of specimen of low water content is greatly.5.By means of research to the pore-pressure together with time's relationship curves of these tests of three-strain compressing consolidation-creep, we can see that the rule is, inclining to be steady on the partial stress action of each grade. With the stress level increasing, the pore-pressure is also increasing. This illustrates that creep deformation may cause pore-pressure rising below the term of consolidated-undrained. The changes of creep deformation and pore-pressure possess have the sameness rule. In terms ofmechanism, they are aroused by the sluggish effect that the adjacent pellets come into being in the soil mass medium.6. By means of research to drainage volume with time's relationship curves of these tests of three-strain compressing consolidation-creep, it shows that, on the loads (partial stress) per step action, drainage volume rise continuously with the time increasing. This illustrates that consolidation deformation of soft clay constantly happens in the coupled process of consolidation and creep. Below Stress level action, drainage volume increase much on the moment of loading, and then add slowly, finally hurrying along one by one to steadies. Stress level gets higher later, drainage volume are little, with the time increasing, then add slowly, finally hurrying along one by one to steadies.7. Uniting the test data of consolidation-creep, the fit has been underway to test's curves of consolidation-creep by the means of the application mathematical statistics and the empirical formula of every the test curve has been obtained. By means of analyzing and investigating empirical formula, the nonlinear elastic-viscous model of consolidation and creep has been established. The model's flexibility is depicted with Duncan-Chang model of instantaneous elasticity; the model's viscosity is depicted with Burgers model. Moreover the parameter in Burgers model has been revised. On the basis of consolidation-creep aspect of model and tests data, experience value of parameter in revision's Burgers theory model was requested out by means of the mathematical statistics.8. The fundamental differential equation of consolidation and creep was built on the basis of coupled model of consolidation and creep. The numeric analysis to the fundamental differential equation was carried by the finite element method. Finite element equation of consolidation and creep of the soil mass with the increment shape expressed was established by the method of weighted residuals. The calculator program of coupled problem of consolidation and creep was recompiled with the FORTRAN language basing on the TDBC-95 program.9. The project instance makes known: The finite element program can be used to analyze the deformation of soft clay ground. Computational solution shows: The finite element program is applicable; the computational solution of the deformation of soft clay ground is still closer to the real situation.