| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系碩士在職專班 === 107 === Quick draining of rainfall in backfill around behind retaining wall by retaining wall drainage holes is critical for the soil and water preservation conservation performance of retaining wall. However, retaining wall drainage hole is commonly clogged by lacking adequate drainage filter or drainage device. Clogged drainage leads to structural overload, even failure of retaining wall. The failure of retaining wall worsens landslide disaster. With laboratory experiment, this paper first examined the turbid water drainage and sediment drainage of hemisphere type drainage device and old sheet type drainage device under conditions with or without graded boulder in backfill around. Then, for various seepage dip angle, the theoretical maximum turbid water drainage and sediment drainage (hollowing) of drainage holes of plum blossom type (staggered) configuration are derived. The experiment results show that without graded boulder in backfill around, old sheet type drainage device has turbid water drainage ratio of 7.09% and sediment drainage ratio of 61.54%; with graded boulder in backfill around, old sheet type drainage device has turbid water drainage ratio of 51.75% and sediment drainage ratio of 12.88%. In both cases, sediment drainage ratio increases rapid seriously because of turbid water drainage ratio increase. Without graded boulder in backfill around, hemisphere type drainage device has turbid water drainage ratio of 6.36% and sediment drainage ratio of 22.86%; with graded boulder in backfill around, hemisphere type drainage device has turbid water drainage ratio of 45.24% and sediment drainage ratio of 2.81%. By experiment results, the 12.88% sediment drainage ratio of old sheet type drainage device is about 4.58 times of the 2.81% sediment drainage ratio of hemisphere type drainage device. Hence, it is verified that the hemisphere type drainage device (plastic filter stones in hemisphere) has less sediment drainage and will not hollow backfill behind retaining wall. Conclusion of this paper provided a reference to department of designing and planning and engineering, those who designed always depend on the designing by empirical, because of bother in lack of proper criterion. To avoid from the reinforce concrete over designed, or lack of filter layer of retaining wall happened repeatedly.
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