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With the rapid developentment of Kunming’s Urban and rural construction, the problem of soft soil foundation has become increasingly prominent and complex. In the Dianchi Lake Basin, the soft soil which is the poor of Engineering geological nature, especially the peaty soil distributes widely. Taking Kunming as an example, North geological conditions are relatively good and suitable for the construction of underground works, the Southern district is the poor geological conditions and has a large number of soft soil, which is not easy to build underground and high-rise buildings and brings many problems to the Kunming’s economic construction and urban development. With peaty soil as a material, the paper has studied the relationship and discipline between soil pressure and soil deformation.Instruments used in this experiment are Multi-point displacement meter sensor (Soil deformation meter), earth pressure cell and pore-water pressure gauge. The accuracy of these three instruments is very high, which can achieve the purpose of this experiment. By the means of real-time monitored for soil deformation, the paper draws a series of deformation data. And then analysising the data monitored, we come to the relationship and discipline between soil pressure and soil deformation and establish their constitutive equations. In this experiment study, I draw the following three important conclusions:(1) The peat soil is elastic-plastic body. Under the effect of the pressure in the upper part, the soil body occurred elastic deformation, also did in the occurrence of plastic deformation, because of the peat soil’s non-restorative in plastic deformation, so when the upper part of the pressure unloading, although the soil occurred deformation, this part mainly belong to elastic deformation. When the upper part of the pressure changes, the soil in different locations have different sizes of the mutation, and this not only be related with the size of the upper part of the pressure, but also with the number of the water content in peat soil. The sizes of the mutation reflect the soil’s elastic properties at the conditions. In the subsequent course of the experiment, soil deformation should be divided into two parts to consider:Firstly, in the loading process, the deformation of soil mutations is mainly plastic deformation, Secondly, in the unloaded (plus water) process, the deformation of soil mutations is mainly caused by the expansion of the soil. The expansion of the soil incessantly affect the deformation of soil, only when the soil deformation increment is very small, the soil could reached a steady state, at this moment, the upper soil pressure and swelling force reach a power balance.(2)In the process of the experiment, the change of the pore water pressure appears abnormally. In the ordinary course of events, the pore water pressure decreases as the water level declines, it is proportional to the height of water level. However, with the proceeding of experiment under the conditions of constant pressure and seepage, the upper-most part of the pore water pressure firstly decreased and then increased, while other locations of the pore water pressure is continuously lower. In the initial stage of seep conditions, water-carrying capacity is comparatively large, while the one in the stabilization phase and the end stages is small. Under the effect of the upper pressure, the soil is deformed, at the same time, the outflow of water aggravates the soil deformation, which may lead to pore water not flowing timely, and the water flow channel is already sealed. With the increasing of soil deformation, pore cavity gradually reduces, pore water pressure is more and more large, which resulted in the phenomenon of abnormal changes in water pressure. This phenomenon is called the pore water lock.(3)Through the soil deformation and pore water pressure and soil pressure of the real-time monitored, according to Terzaghi effective stress principle and the related theory of elasticity and plasticity, the paper obtains constitutive relation of stress and strain, combines with the measured test data to establish a constitutive equation between peat soil stress and strain, which provides a theoretical basis for the relationship between soil deformation and the soil pressure.
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