水泥泥炭与纤维基干喷生态护坡基材配方优化及现场试验

为修复各种工程建设形成的边坡生态系统,获得干喷生态护坡基材的配制规律,该文以一种新型干喷生态护坡基材为研究对象,以生态基材组分中的泥炭、纤维、水泥、土壤改良剂和保水剂为5个因素,各取4个水平,开展了多指标多因素正交试验探索各因素和水平对狗牙根的发芽和生长状况的影响规律。结果表明:影响植物生长和出芽的因素的重要性从大到小依次为水泥、保水剂、聚丙烯酰胺(polyacrylamide,PAM)、纤维、泥炭。纤维和泥炭含量对植物出芽率影响不显著,植物出芽率与水泥含量呈线性关系,基材水泥含量越高植物生长越差;为确保植物较好生长,水泥体积百分比不宜超过10%。对于湖北三峡翻坝公路区域,适合狗牙根生长的最优基材配比:除当地泥土外,泥炭20%,水泥5%,PAM0.05%,保水剂0.15%,纤维40%。基材p H值与时间呈较好线性关系,植物本身具有调节p H值的能力,随着时间的增长,基材p H值逐渐降低,逐渐接近中性。该文结果对三峡翻坝公路所处长江中游及鄂西南地区生态护坡基材配比具有指导意义;研究所得规律,同样适用于土壤气候条件相似的其他中部地区;试验、分析方法亦可适用于其他区域生态护坡基材配比研究。

Optimization on formulation of peat-fiber-cement-based dry-sprayed substrate for slope ecological protection by site experiment

Abstract: To rehabilitate the damaged ecosystem of slope formed in civil engineering, Chinese Engineers developed the technology of ecological protection of slope by shotcreting dry-sprayed substrate at the beginning of 21st century based on foreign relative technologies. The technology which suits for steep rock slopes has been widely used in China since it came out. To improve the erosion resistance of the dry-sprayed substrate, fiber and (or) cement were usually included in the substrate formulation to reinforce the substrate. So far, though some research have been conducted about the technology, few studies concerned the formulation design of the dry-sprayed substrate. Aiming at this problem, site experiments with orthogonal design were carried out, in which a new type of plant fiber was used to reinforce cement-based substrate which included five components: peat, plant fiber (made of crushed straw), cement, top soil, water-retaining agent (polyacrylamide, PAM). In this paper, the five components were treated as five factors (four levels for the content of each factor) and plant (Bermuda grass) growth index, pH value of substrate as dependent variables, and the orthogonal experiments were conducted to investigate how the factors and levels influenced plant germination, coverage rate and growth of plant. The results showed that from high to low, the order of importance of factors influencing plant germination and growth was cement, water-retaining agent, PAM, fiber and peat. The content of fiber and peat had no significant effect on plant germination, while cement content had observably adverse effect on germination rate. The cement content (volume ratio) had a linear relationship with the germination rate, and the cement content in the substrate should be less than 10%. For the slope's ecological protection project along the roads in the Three Gorges area, most formulations of the substrate employed in this study could be used while the optimal formulation (volume ratio) for bermuda grass was 34.8% local top soil, 20% peat, 5% cement, 0.05% PAM, 0.15% water-retaining agent, and 40% fiber. In addition, it was found that the plant had the capacity of reducing pH value of the substrates, which had a linear relationship with time, and gradually decreased to eight after 70 days. The results presented in this paper will have the guiding value for the substrate design when the slope's ecological protection projects are carried out in the region of middle or lower reaches of Yangtze river, and the principles found in this paper also suit for the districts with similar soil and climate conditions. The approaches used in this study can be employed to conduct substrate design for the slope's ecological protection in other districts.