| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 101 === Wood pile revetment in Keng-Nei-Keng Ecological Engineering Demonstration Area, which has been built for two years, and wooden constructions imitating Azekura-zukuri style retaining walls in Miao-Chien-Keng Ecological Engineering Demonstration Area, which has been constructed for four years, in Erh-shuei Township, Changhua County, are studied. The Azekura-zukuri style retaining wall, 3m high and 27.5m long, is established in the environmental areas with high vegetation but little light intensity. The wood pile revetment, with the surface height 1.5m and the length 24.6m, is established in wild torrents with lower vegetation and permanently direct sunlight. The environmental differences in wood appearance change, vegetation, and light intensity from the completion of the constructions to current situation are organized, and non-destructive testing is utilized for testing the degradation of wooden constructions so as to compare the effects of types and location of wooden constructions and environmental differences on the wood degradation. The non-destructive testing items contain wood hardness tester, depth of wood penetration (pilodyn), ultrasonic testing, and moisture content test.
From the investigation of non-destructive testing, the overall moisture percentage of the Azekura-zukuri style retaining wall shows 31.44±4.02 %, where the higher moisture percentage appears on the wood close to the surface and the average depth of penetration of Pilodyn wood hardness tester reveals 27.03±9.13 mm. The overall moisture percentage of the wood pile revetment presents 30.28±3.93 %, and the average depth of penetration of Pilodyn wood hardness tester appears 21.22±5.55 mm. The results show the serious degradation of the Azekura-zukuri style retaining wall, possibly because of dense vegetation. The two wooden constructions present more serious decay at the parts close to the surface, where the wood pile revetment under the surface is almost decayed that the appropriateness should be assessed. In terms of ultrasonic measurement, the ultrasound mean of the Azekura-zukuri style retaining wall in the studied area shows 3,393 m/sec, and 4,224 m/sec of the wood pile revetment. By calculating the sound velocity compensation, the degradation of the Azekura-zukuri style retaining wall is more serious, and the wood pile revetment above the ground reveals better conditions than the entire wooden construction.
A theodolite is utilized for permanent detection of three-axis position. Currently, the two wooden constructions present little modification that the overall constructions are regarded stable. Assuming wooden constructions as rigid structures without fracture or separation of wood structures and settlement damage to the basis, the stability analysis still shows the two wooden constructions being stable.
Finally, the considerations for the planning and management of wooden constructions and current wooden constructions requiring for maintenance are organized, and the maintenance regulations are proposed, expecting to increase the service life of wooden constructions for promoting the ecological engineering.
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