公路边坡绿化覆盖物水土保持效果试验研究

公路施工过程中产生大面积裸坡,植物无法迅速生长,土壤流失量也特别大,铺设覆盖物是一种有效而廉价的保持水土的方法。为了研究不同覆盖物在坡面的水土保持效果,该文基于自制的室内人工模拟降雨器,在对其进行标定后,对已覆盖无纺布、遮阳网或草帘子的正在进行绿化喷播施工的模拟公路边坡进行人工模拟降雨试验,对3种覆盖物在公路边坡的水土保持效果进行了详细描述。3种覆盖物下坡面的径流量、径流系数、泥沙浓度以及产沙量均明显(P=0)小于裸坡的,说明无纺布、遮阳网和草帘子均可以有效的减少公路边坡喷播绿化过程中的水土流失。其中,草帘子覆盖下坡面的径流量(1.9mL/s)比裸坡减小69.9%,径流系数(6.4%)比裸坡减小14.9%,坡面产沙量(1.5g/m2)仅为裸坡的3.4%,且远小于无纺布和遮阳网覆盖下的,说明草帘子对公路边坡的水土保持效果较好。该文为公路边坡绿化施工中覆盖物的水土保持效果提供理论依据,为覆盖物的选择提供科学参考。

Effectiveness of soil and water conservation of greening mulch of roadside slope

Soil erosion is one of the most serious environmental problems in the world. The acceleration of soil erosion is mainly caused by land use changes, and highway construction is an important land use change. Mulch is a good alternative before the establishment of vegetation on slopes, which can reduce the direct impact of rainfall on the slopes and increase the infiltration of rainwater, reducing runoff and soil erosion. In this study, a rainfall simulator was made which is of simple structure and is easy to operate. Rainfall intensity, rainfall uniformity and raindrop diameter were all calibrated and could reach the experimental requirements well. Ten 20-minute rainfall simulations were carried out on each simulated road slope (30°) which was covered variously with shade net, non-woven fabrics, straw mats and nothing, respectively, in order to examine the effects of three kinds of mulch, shade net, non-woven fabrics and straws mat on road slopes in decreasing runoff and soil loss. The aim was to obtain the best effectiveness of soil and water conservation in the process of green construction of road slope. The process of runoff production on the slope was strongly influenced by the effects of the underlying surface conditions. The ANOVA showed that there were significant differences among the hydrological responses of the slopes depending on the different mulch. The surface runoff curves are logarithmic. The highest average runoff coefficient was determined for the bare slope (21.3%). Runoff coefficients of slopes with shade net and non-woven fabrics were 13.5% and 18.9% respectively. Average runoff coefficients were lower on the slope with straw mats (6.4%). The three kinds of mulch were all successful in reducing the runoff rate. The average runoff rates were 4.2 mL/s, 5.8 mL/s and 1.9 mL/s for slopes with shade net, non-woven fabrics and straw mats, respectively, which were all much lower than that of bare slope (6.6 mL/s). The same behavior was observed for the peaks of runoff rate. Some differences were also detected in the sediment concentration in runoff water. The greatest erosion was detected on the bare slope, where average sediment yield was 5.7 g/L and total soil loss was 44.2 g/m2. The soil loss from the slopes covered with shade net and non-woven fabrics was approximately 8 g/m2 and 5 g/m2 respectively. The lowest erosion was determined for the slope covered with straw mats (with 1.0 g/L as an average sediment yield and 1.5 g/m2 as a average total soil loss). Sediment yield data were also higher for the bare slope (5.7 g/L) than for the slopes covered with shade net (2.4 g/L) and non-woven fabrics (1.9 g/L). The same behavior was observed for the peaks of sediment yield: the highest value for the bare slope was 8.1 g/L, and the lowest value for the slope with straw mats was 1.8 g/L. The three kinds of mulch all significantly (P=0) decreased runoff and soil loss rates compared with the bare slope. What is more, straws mat had the best effect as it induced the lowest runoff (1.9 mL/s), runoff coefficient (6.4%) and soil loss (1.5 g/m2).