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利用工厂产品聚烯烃材料代替传统的梢料和石料构成透水的整治建筑物——网坝(见附照片1),1975年开始进行现场试验,迄今已在十余处较大规模的中间试验工程中获得了良好的效果。从现场地形变化及其实际效果来看,网坝能够缓流促淤,护岸保滩,防止侵蚀,加速涨滩,有利于围垦;能够集中水流,刷深航道,改善航行条件;能够改变水流内部结构,促成或减弱环流强度,防止凹岸冲刷并能够消减波能和减轻海啸等灾害性的破坏。目前获得的具体结果有以下几点:1.在航道整治中采用网坝促成环流和集中水流,刷深航道,并使冲刷下来的泥沙淤高边滩,起促淤固滩作用。尤其是对防洪要求高、不容许在河槽中构筑实体建筑物的通航河流,网坝更具有优越性。2.缓流促淤的效果与网坝的总体布置和网坝的透水程度密切相关,条件适当时,如已进行的现场试验中每天淤积可达一厘米,一般情况下都能发挥缓流促淤作用(见附照片2)。3.网坝对上、下游都能起缓流促淤作用,下游的淤积范围远较上游为大,一般可达600倍坝高以上。但对上游的范围尚有待探索。4.网坝的缓流作用大小随其透水程度而变化,透水系数α>0.3时(透水系数α=网体单位面积中的空隙面积/≧网体的单位面积),透水坝的缓流促淤作用比实体坝有效,当透水系数α≤0.3时,其作用将接近于实体坝。5.网坝结构简单,有时,一道网坝就能起缓流促淤,集中水流,改变水流结构和消减波能等多种作用。但在水流和地形复杂时却常需布置多道网坝,才能发挥作用。6.由于网坝是透水的轻型建筑物,对水流影响较小,可在实施后观察它的作用和效果;不理想时,既可在现场进行局部的修正,也能很容易地完全折除。能发挥试验性工程的良好作用。
The use of factory products polyolefin material instead of the traditional shoots and stones to form a permeable remediation building - Network Dam (see attached photo 1), started in 1975 on-site tests, so far in more than ten large-scale pilot projects In the good results. From the change of the terrain and its actual effect, the dam can slow flow and silt up, protect the bank and protect the beach, prevent erosion, accelerate the rising beach and help reclamation; can concentrate the water flow, brush the deep waterway and improve the navigation conditions; can change the internal flow Structure that facilitates or attenuates circulation strength, prevents erosion of the dimples and reduces wave energy and mitigates disastrous damage such as tsunamis. The specific results obtained so far include the following: 1. In the waterway regulation, the use of a network dam to promote circulation and concentrate the water, brush the deep channel, and make the erosion of the silt high side beach, promote silt solid beach role. Especially for the flood control requirements, does not allow the construction of solid river structures in the river navigation, web dam even more advantages. 2. The effect of slow flow and siltation is closely related to the overall arrangement of the dam and the water permeability of the dam. When the conditions are appropriate, as much as one centimeter per day of on-site test has been carried out, under normal circumstances, Silt effect (see attached photo 2). 3. The dam on the upstream and downstream can play a role in slowing sedimentation, the downstream sediment deposition is much larger than the upstream, generally up to 600 times the dam height. However, the scope of the upper reaches remains to be explored. (4) The effect of net dam on the flow rate changes with the degree of water permeability, permeability coefficient α> 0.3 (permeability coefficient α = mesh area per unit area / ≧ net unit area) The silt effect is more effective than the physical dam, and when the water permeability coefficient α ≤ 0.3, its effect will be close to that of the solid dam. 5. The structure of the net dam is simple. Sometimes, a net dam can play a variety of roles, including slow flow and siltation, concentration of water flow, change of water flow structure and abatement of wave energy. However, it is often necessary to arrange multiple network dams in the complex flow and topography in order to play a role. 6. Because the dam is a water-permeable light building that has little effect on water flow, its effect and effect can be observed after it is implemented. If it is not ideal, it can be locally corrected in the field and easily and completely dismantled . Can play a good role in experimental projects.