Research On Rheological Properties Of Reticulate Red Clay In Dongting Basin

Reticulate red clay is familiar in construction of geotechnical engineering around Dongting Lake. So far people pay too much attention to the origin, distribution, structure and elastic deformation of the reticulate red clay. This kind of clay has high strength and it is generally believed that the reticulate red clay has no rheological properties, so there is no research about it. Actually, the reticulate red clay holds rheology, and it affects the stability of foundation(subgrade), foundation ditch, slope and other projects directly. So it's important to study the rheological properties of the reticulate red clay so as to help the design and construction of geotechnical engineering around Dongting Lake. Starting from theories and tests results, the rheological properties of the reticulate red clay are studied in this paper. The main achievements were obtained as follows:(1) One dimensional creep tests with undisturbed and reconstituted specimen of reticulate red clay were performed respectively under different loading conditions. Test results show that the compressibility of undisturbed sample is much more insignificant than that of reconstituted sample; the creep curves of undisturbed sample are rough, and there is no obvious steady creep stage in the curves, while the creep curves of reconstituted sample are smooth and there is an obvious steady creep stage; the undisturbed sample comes to the end of creep deformation much earlier than reconstituted one does. An empirical equation was also derived. A new parameter in the equation can help people forecast the ultimate settling amount of reticulate red clay.(2) Triaxial creep tests with undisturbed specimen of reticulate red clay were also performed. Many testing curves have been drawn and analyzed. Test results show the following:â‘ stress level under which the failure occurs in soil is relevant to the confining pressure;â‘¡when the stress is low, creep behavior of the reticulate red clay is characterized by linear visco-elastic properties, while the stress is high, creep behavior of the reticulate red clay is characterized by nonlinear properties;â‘¢the degree of nonlinearity get higher along with the stress level. Singh-Mitchell model was applied to describe the rheological properties of the reticulate red clay based on the triaxial tests. The model describes the stress-strain-time relationship of the clay under the deviatoric stress level from 20 percent to the 80 percent well.(3) Loading rate effect of the reticulate red clay was studied. The results show that in the direct shear tests and the triaxial shear tests the reticulate red clay is different from other clay in terms of the relationship between shear strength and shear rate.