Study Of Post-construction Settlement Mechanism Of Soft Soil Foundation And Develop Equipment For The Pore Pressure Observation

With the development of national construction enterprises, infrastructure investmenthas been enlarging gradually, while the land resources become increasingly scarce. Inparticular, the rapid development of our national road network results in that manystructures have to be built on soft soil foundation. However, the soft soil foundationwith high moisture content, poor permeability, large compressibility, and weak strengtheasily leads to foundation settlement. It threatens the safety of buildings seriously. Manyscholars always engage in researching the soft foundation treatments. However, throughthe observation of soft foundation settlement, there are always some treatments that cannot reach the ideal effect and even some in contradiction with existing theories. Hence,research on soft foundation settlement mechanism is an extremely meaningful work.The classical consolidation theory only applies to saturated soil. On the contrast, thetheory suitable for the unsaturated soil has not been established yet. Due to lack of theequipment for unsaturated soil research, the study on the mechanism of unsaturated soilsubsidence is hindered largely.The main purpose of this paper is to study the equipment which is used to observepore pressure of unsaturated soil.First, analysis and comparison of the main settlement consolidation theory ofsaturated and unsaturated soil in the domestic and overseas areas are presented.Meanwhile, combined with road settlement, this paper also elaborates both researchstatus of settlement mechanism. The analysis revealed that the existing settlement ofunsaturated soil consolidation theory can not reasonably explain some settlementphenomena in the experiment and engineer. Therefore this paper puts forward to theview that unsaturated soft soil will produce the negative pressure with falling watertables which effects foundation settlement.Then, a new type of unsaturated soil pore pressure observation equipment,measuring equipment of pore pressure by rope length difference under hydraulicpressure in the U-type tube, has been designed and developed in order to verify theviews of this paper.The new equipment can be used to observe unsaturated soil pore pressurequalitatively or quantitatively，verifying the existence of the pore negative pressure andthe influence mechanism that how unsaturated soil pores pressure impacts on settlement.Thus settlement consolidation theory applied to unsaturated soil will be consummated. Finally, this paper also introduces the following experiments and engineeringapplications. The design, development and application of unsaturated soil pore pressureobservation equipment has great significance for research on soft soil foundationsettlement mechanism, consummating consolidation theory and soft foundationtreatment.