水庫淤泥於水泥噴凝植生敷蓋技術之應用研究

Abstract

水泥噴凝植生敷蓋技術(Shotcrete Vegetation Mulching Technique, SVMT)係為一可應用於陡峭邊坡、噴凝土擋牆等坡面困難工址之植生技術。此一技術於植生基材中以特定比例將土壤、腐植質、水泥、綠化添加劑以及草種等予以混合，使其可於上述困難工址上重新營造一適合植物生長的環境。本研究主要目的即在於透過實驗室及現地試驗，研擬以水庫淤泥全部或部分取代植生基材中土壤之方法，期能藉此提供一個處理水庫淤泥的應用方向。另綠化添加劑係屬一專利產品，內含保水劑、長效肥與土壤中和劑等，其成分及配方屬商業機密、不易獲得。為突破此限制，本研究成功的研發出其他基材及相關配比代替之。 本研究所採用之淤泥係採自石門水庫。在實驗室試拌中，以不同土壤、水泥、蛭石、有機肥及中和劑等植生基材為變因，共進行了五階段試驗，總計完成77種配比之試拌工作。其後，以試體強度4~6 kg/cm2、土壤pH值5~8為目標，並搭配植生覆蓋度進行最佳配比的篩選，供後續實驗室模擬現地試驗及現地示範區噴植之用。由於水庫淤泥黏土含量較高，易產生黏土易乾裂及土壤含水量高時將使強度大幅下降，不利於抵抗降雨沖蝕等問題。本研究透過多次嘗試試驗將此問題一一克服。依據示範區於齡期112天調查結果顯示，本研究達到土壤強度足夠(2.5~3.5 kg/cm2)，酸鹼值適中(pH 5~8)，土壤表面完整(沒有發生龜裂)，植生覆蓋密集(覆蓋度達9成)且能提供保護土壤並防止沖蝕的能力。因此，本研究所使用的石門水庫淤泥當作試拌土壤以及利用硫酸亞鐵、蛭石與蔗渣堆肥以替代綠化添加劑(此乃專利產品)的這一改良技術確可具有取代原先技術的功效，雖在土壤酸鹼度部分仍有待稍微改善之處。

The Shotcrete Vegetation Mulching Technique (SVMT) can be applied to revegetate the plants on steep slopes, shotcrete retaining walls and other difficult sites for revegetation. Using this technique, soil, humic substances, cement, greening additives and grass seeds are mixed in a certain ratio and applied on the sites which are difficult to be revegetated, and to foster an environment which is suitable for plants to grow. The purpose of this study is to develop an approach to partially or completely replace the planting materials with the sediment deposited in the reservoir through the laboratory and field tests, so that a new method may be proposed to manage the sediments of reservoirs. In addition, because greening additives is a patent product, which contains water retaining agent, slow release chemical fertilizer and soil neutralizer, it is limited to be promoted. In this study, new materials and mixing formula are developed to replace the greening additives. The sediments used in this study were collected from Shihmen reservoir. During mixing trials in the laboratory, different ratios of soil, cement, vermiculite, organic fertilizer and neutralizer were used as planting materials. Tests were divided into five stages, and 77 mixing ratios were experimented in the laboratory. By considering the targeted strengths of the specimens (4 to 6 kg/cm2), targeted pH values of the soils (5 to 9) and higher vegetation coverage rate, a few specimens with better mixing ratios were selected for simulated field tests. Due to high clay content of the reservoir sediment, some disadvantages were found, which included that the clay tended to crack during drying and soil strength drastically decreased while soil moisture was too high. However, these difficulties had been overcome and mixing ratio No. g-24 was finally selected and applied on the demonstration sites. For field tests, the survey result showed that soil strengths were adequate (2.5~3.5 kg/cm2), pH values were moderate (pH 5~8), soil surface were integrated (no crack) and plants close completely covered the slope (the vegetation coverage rate was higher than 90%) at the end of 112th days. It indicated that the developed SVMT method in this current research could reduce soil erosion and fully met the needs of plant germination and growth. Hence, the mixture of reservoir sedimentation, cement, expanded vermiculite, bagasse compost and ferrous sulfate in a certain ratio can perform better function than original SVMT (with patented greening additives), even though there is room for improvement in soil pH in the future.