Development And Experimental Research Of The Equipment For Fully Automatic And Quickly Measuring Soil-Water Characteristic Curve

The soil-water characteristic curve is an important foundation in the study of soil-water characteristics of unsaturated soils.It can quantitatively analyze the water holding capacity of soils under the influence of external conditions and predict the unsaturated mechanical characteristics of soils.It is of great significance to the prevention and control of slope instability and other engineering disasters.The indoor test takes a long time to obtain the soil-water characteristic curve,and it takes a month to several months to measure a drainage curve in a balanced state.Limited by the conditions of the test equipment,there are not many experimental studies on the soil-water characteristic curve under the action of dry-wet cycles and vertical stress.Therefore,improving the equipment to speed up the test has also become a research hotspot.This paper is devoted to studying how to speed up the test of measuring soil-water characteristic curve,and then develop a fully automatic and rapid soil-water characteristic curve measurement equipment,which can quickly determine the soil-water characteristic curve under the action of dry-wet cycle and vertical stress.The thesis first measured the basic physical and mechanical indexes of high liquid limit silt through indoor tests.Then the GEO-Experts stress-related pressure plate instrument was used to measure the soil-water characteristic curves of the soil samples under four different compaction states,so the measured data were obtained and the shortcomings of the equipment were summarized.Then,the performance of different microporous membranes was measured by indoor test method,and the soil-water characteristic curve of the soil sample under the same condition was measured by the GEO-Experts stress-related pressure plate instrument combined with the microporous membrane with the best test effect.The test results show that the ultra-thin thickness of the microporous membrane,the uniformly distributed pore size,and the effect of "anti-air and non-waterproof" make it possible to replace the clay plate to effectively determine the soil-water characteristic curve.And then,based on the above test conclusions and error analysis,equipment improvements were made on the basis of GEO-Experts stress-related Pressure plate equipment.Then,based on the above-mentioned experimental conclusions and error analysis,equipment improvements were made on the basis of GEO-Experts stress-related pressure plate meters,and a fully automatic and rapid soil-water characteristic curve measurement equipment was developed.The equipment has the characteristics of fast test speed,high degree of automation,simple operation and good controllability.Then use experiments to verify the effectiveness and stability of the equipment.Finally,the fully automatic and rapid soil-water characteristic curve measurement equipment is used to determine the soil-water characteristic curve under the action of dry and wet cycles and vertical stress.The test results are good,and the analysis shows that the influence of the dry-wet cycles on the soil-water characteristic curve is greater than the influence of the vertical stress on the soil-water characteristic curve.A revised Fredlund&Xing model is proposed.The prediction model has a good fitting effect on Changsha high liquid limit silt,Badong silty clay,and Dalian silty clay,but has a poor fitting effect on expansive soil and loess.It can provide a reference for the prediction of the soil-water characteristic curve of silt and silty clay after repeated drying and wetting cycles.