| Summary: | 碩士 === 國立屏東科技大學 === 水土保持系所 === 95 === Under the construction of the earth dam (embankment) in the mudstone area of soutern-west of Taiwan, due to the special foundation and climate, there is barely sign of vegetation. And the soil erosion is very serious. The human lives and belongs undergo great threatening. Thus in the research, we collect the fundamental data of the earth dam (embankment) through on-spot investigation, accompanied with erosion observation and handy dynamic cone penetrion test, in order to judge the basic type of soil and analyze the degree of damage. After that, in the laboratory, we adopt the method of SCD Test in Direct shear test to gain the parameter of soil dynamics, and later try to define the leaking line of the earth dam. We also use the software for slope stability analysisto evaluate the stability of the dam (embankment). After cross-examining the results from slope stability analysis and handy dynamic cone penetrion test, we gain the conclusion as follows:
1. According to the survey of earth dike in south-west Taiwan mudstone area, we found out that most of the dikes do not follow the requirement of soil-and-water conservation brochure. Though the height of construction is far lower than restricted, it still caused great damage for it has exceeded the set restriction, such as the excess of front and lower side slopes and height of breakwater from S.W.L.
2. As for the factors to damage, the structure of the earth dike we investigate is simple and the Self-Weightis little so that it does little impact on the substratum. Thus there are no such problems as piping, sinking, sliding and insufficient bearing capacity of the dam base, which are caused by the unsteady substratum. As for the imperfection of the earth dam itself, some commonly seen problems are the erosion, leaking and the slide of the surface slope. These problems often result in serious damage.
3. By handy dynamic cone penetrion test, we could check the inner part of the dam is composed with homogeneous soil or not, in order to use Nc to distinguish the weakest parts inside the dam.
4. The position of weak surface in the inner structure of the dam could differ by the geometric types and soil variables. On the influence of seepage, the intensity of the soil foundation might be slightly different. If the area of the weakest Nc is too close to the ground surface, it is likely to be less stable for the influence of the seepage to the slope. In consequence, to reduce seepage efficiently could strengthen the stability of the slope.
5. The stability analysis could identify the stability of the earth dam (embankment). If accompanied with handy dynamic cone penetrion test, the ultimate outcome would be the more precise and pointed.
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