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Critical State Soil Mechanics Phần 2

Tham khảo tài liệu 'critical state soil mechanics phần 2', khoa học tự nhiên, công nghệ môi trường phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 13 possibilities of degradation or of orientation of particles. The first equation of the critical states determines the magnitude of the deviator stress q needed to keep the soil flowing continuously as the product of a frictional constant M with the effective pressure p as illustrated in Fig. 1.10 a . Microscopically we would expect to find that when interparticle forces increased the average distance between particle centres would decrease. Macroscopically the second equation states that the specific volume v occupied by unit volume of flowing particles will decrease as the logarithm of the effective pressure increases see Fig. 1.10 b . Both these equations make sense for dry sand they also make sense for saturated silty clay where low effective pressures result in large specific volumes - that is to say more water in the voids and a clay paste of a softer consistency that flows under less deviator stress. Specimens of remoulded soil can be obtained in very different states by different sequences of compression and unloading. Initial conditions are complicated and it is a problem to decide how rigid a particular specimen will be and what will happen when it begins to yield. What we claim is that the problem is not so difficult if we consider the ultimate fully remoulded condition that might occur if the process of uniform distortion were carried on until the soil flowed as a frictional fluid. The total change from any initial state to an ultimate critical state can be precisely predicted and our problem is reduced to calculating just how much of that total change can be expected when the distortion process is not carried too far. Fig. 1.10 Critical States The critical states become our base of reference. We combine the effective pressure and specific volume of soil in any state to plot a single point in Fig. 1.10 b when we are looking at a problem we begin by asking ourselves if the soil is looser than the critical states. In such states we call the soil wet .