Research On Physicochemical Properties Of Growing Basis Material For Eco-protection Of Slope

Substrate, which is the most important material in eco-engineering for rock slope protection (EERSP), is the substance basis for stable growth of vegetation. The function of substrate relies on the effects of functional material under condition of limited substance. The primary functional material, including cement, polyacrylamide (PAM), organic matter and straw fiber, are investigated quantitatively with functional effects. The results show:(1)Cement takes the important part in improving substrate intensity. When the proportion of cement is more than 12%, the unconfined compression o rise distinctly with the cement. At the beginning, cement affects pH of substrate obviously, but sometime later, the pH get steady, lower than 7. 5; after grass planting the growth of grass can adjust the pH. Therefore, the effect of cement on the substrate's pH is not big problem. At first, the cement may restrain the growth of grass, but the effect will be very low when the grass grows up; however, when the proportion of cement is more than 15%, the surface of substrate can appear crust formation, it can baffle seed burgeoning badly, then the overlay rates may be very low. The suitable proportion of cement is 12%～15%.(2)PAM can obviously improve the density,interspace,aggregates of substrate. PAM can increase the content of water of substrate, delay runoff time, and increase the number of droughty days; it can adsorb or release water, but the ability may decline after a long time. PAM has well capability of nutrient conservation, it enhances the slow-release of nutrient, after about a year, the wastage of substrate keeps in a low level(lower than 5%). When the content of PAM more than 1‰, the rate of germination descends rapidly, the height of grass also descends. Therefore, we couldn't increase the dosage of PAM illimitably, its suitable dosage is 0.8‰-1‰.(3) Organic matter improves the intensity and nature moisture of substrate, offers good condition for the growth of vegetation cover。It can affect the rate of solid, liquid and gas of substrate greatly, especially on the rate increasing of liquid. When the proportion of substrate of organic matter is 15%, the horizontal contraction rate (r_con) is the lowest; more than 15%, (r_con) and the max interstice increase fast. Therefore, the suitable content of organic matter is about 15%-20% for the vegetation, more than it, the organic matter can lead too high proportion of substrate's liquid, result in the death of vegetation; lower than it, the substrate may be too flinty, short of water, then not suit for the growth of vegetation.(4) Appropriate straw fiber can improve the shear strength of substrate, reduce the soil erosion, delay runoff time, decrease the cranny width of substrate, it takes important part in the substrate stabilization. However, too high content of straw fiber would bring bad infection, on the examination, the suitable dosage is about 3%～4%.