Evaluation Of Uniformity And Preliminary Mechanical Properties Of Simulated Samples Of Soft Soil Containing Bubbles

It is well known that Shallow gas widely exists in marine engineering geological environment,and often exists in the form of closed bubbles in silt with organic matter,which distributed in shallow stratum.In recent years,due to the lack of knowledge about mechanical properties of soft soil with bubbles at the bottom of sea,a large number of accidents have been encountered in the process of exploration and development of marine resources.With the rapid development in the field of marine engineering,we further need to understand the mechanical characteristics of the bubble in soft soil on the seabed,and reveal the mechanism of its disaster,so as to provide a support for the construction and resource development in offshore area.It is very difficult to take samples of soft soil with bubbles in the bottom of the sea because the distributed gas can easily escaped which will leads to the breakage of the soil structure in its initial state.This paper mainly research the method of preparation of samples of soft soil with bubbles in the laboratory,as well as provides an effective way to assess the size and distribution of uniformity of the bubble in soil samples from a microscopic perspective and analyzes the preliminary mechanical properties of the prepared soft samples.The main contents and conclusions are as follows.(1)Preparation of soil samples with bubble.The soft soil samples with bubbles were prepared by mixing powder of zeolite saturated by methane with soil and then adding water to substitute gas stored in zeolite power.According to the changes of volume,void ratio and moisture content of soil sample during consolidation test,the initial gas content of soil samples can be calculated,and a linear relationship between the amount of power of zeolite and the gas content of soil samples is obtained,which provides a basis for subsequent massive preparation of soil samples with bubble.(2)Evaluation of uniformity of soil samples with bubble.Put the prepared soil sample into a custom-made hollow cylindrical PMMA pipe,and then perform a CT scanning test,The processing of the obtained CT immage was completed by a software named VG studio and the spatial and size distribution characteristic of bubbles is obtained.According to the principle of uniformity which can assess the spatial and size distribution of bubbles can be drawn.(3)Experiments for mechanical properties of soft soil containing bubbles.Vane test and conventional triaxial compression test conducted on samples with different contents of powder of zeolite containning no methane showed that the shear strength of samples are virtually not influenced by powder of zeolite added in the process of samples preparation.Vane test were performed on soft soils with bubbles with different gas content.It was found that the shear strength of soft soil with bubbles reduce as the gas content increased.The triaxial compressions test of soft soil containing bubbles was carried out,and the shear strength of the soft soil containing bubbles was found to be improved after consolidation.