Research On Creep Of Reticulate Red Clay Under Stepped-load And Constant-load

Reticulate red clay distributes widely in southern China, especially in the middle and lower reaches of the Yangtze River region. City infrastructure construction and all kinds of geotechnical engineering construction in these areas will often encounter this kind of soil. Reticulate red clay is a kind of cohesive soil with creep properties; the characteristics greatly influence the long-term stability of the various types of structures with reticulate red soil as bearing layer. Therefore, it is very important to make a systematic research on creep properties of the reticulate red clay for survey, design, monitoring of geotechnical engineering.The creep properties of the reticulate red clay can be studied by creep tests. The creep tests can be divided into field creep experiment and indoor creep tests. There are two kinds of loading mode in indoor creep tests:one is stepped-load; the other is constant-load.In this paper, undisturbed reticulated red clay specimens from Changsha Hunan province, China were tested under indoor one-dimensional creep tests under constant-load and stepped-load. The creep relationships between stepped-load and constant-load have been studied. The main research contents and conclusions are as follows:1) Undisturbed reticulated red clay specimens were tested under indoor one-dimensional creep tests under stepped-load and constant-load. Tests results showed that:in the two case, one-dimensional creep deformation of the reticulate red clay appeared decaying creep process; creep strain rate decreased as the creep time increasing and tended eventually to0; creep stabilized eventually.2) Undisturbed reticulated red clay specimens were tested in monotonic initial loading, unloading and reloading with different creep stress level. Tests results showed that:there was obvious creep deformation occurred at each stress level in initial loading, unloading and reloading; the creep deformation increased significantly as the increasing of creep stress. In the unloading process, when the stress level become OkPa, the creep deformation eventually retained plastic deformation which can not be irreversible; the creep deformation under reloading was significantly smaller than that of initial loading.3) Analysis of the stage loading and load creep’s test results showed that there has a linear relation between the ratio of creep time and creep strain and creep time in both stepped-load and constant-load creep; there was also a linear relationship between the slope of the linear relationship under stepped-load and that of constant-loading. Therefore, the creep deformation of stepped-load can be used to calculate the creep deformation of constant-load.