Development of the methods of safety evaluation in land improvement facilities

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1. Safety evaluation in seepage flow The safety factor to the seepage failure of the foundation ground is defined by using the prismatic failure concept. The limit water head is analyzed in case- of two dimensional concentrated flow by varying the setting depth of sheet piles and the width of digging of ground. As a result, it is clarified that the smaller the width of digging and the deeper the setting depth is, the more decreasing the stability to the seepage becomes. In addition, it is also shown that the stability of the ground decreases when the ratio ofanisotopic:2. Hydraulic fracturing in fill material Considering the tensile failure generally occurs in the material when its character changes, soil is thought to cause a similar mannec Tri-axial compression tests are conducted on samples taken from a foundation in a small earth dam to examine the generation of the vertical crack with varying water content As a result, it is confirmed that a vertical crack occurs at a considerably … More early stage and lower water content in the experiment, so it suggests the hydraulic fracturing possibly occurs when reservoir water level rises.3. Safety evaluation in concrete structures The wedge insertion technique under two axial stresses is performed. In two types of concrete with river gravel and crushed stone, each breaking energy is obtained from the measurement of load-opening displacement As a result it is clarified that the breaking energy decreases compared with the case of the uniaxial stress, and the one with crushed stone is larger than that with the river gravel. In addition, the multi straight line approximation method is applied from the measurement data. It is also shown that the shape of softening curve differs each other, and the Young's moduli decrease, increasing in the compressive stress ratio.4. Reliability design of reclamationtlvke A calculation method of probability of liquefaction in reclamation dyke is proposed considering the spatial variability of soil parameters for the dynamic strength, N-values, median grain size, fine contents and the statistical characteristics of the earthquake occurrence. Using this method, the reliability design of the sand compaction piles is discussed for the ground improvement against the liquefaction. As a result, it is shown that the optimum sand replacement rate is determined so as to minimize the total cost Less