坡面岩体–基质–根系互作的力学特性

INTERACTIONAL MECHANICAL CHARACTERISTICS OF ROCK-SUBSTRATE-ROOT SYSTEM

通过试验对岩石边坡植被护坡工程坡面岩体–基质–根系互作的力学特性进行了初步探讨,研究了基质–根系复合体自身的抗剪、抗拉及其与岩体间的抗剪特性;探明了抗剪强度、抗拉强度与复合体含根量、含水量等因子间的关系及时间尺度效应。研究结果表明:基质–根系复合体与岩体间的抗剪力主要由摩擦力及生物作用力组成,抗剪强度随含水量的增加而减小,随含根量增加而增大,均表现出对数函数关系,含水量对摩擦力及生物作用力均产生影响,含根量主要影响生物力部分;由于植物根系的存在,复合体具有了抗拉特性,其抗拉强度随含根量增加而增大,随含水量的增加而降低,并与两者间存在较显著的函数关系;复合体抗剪强度τ与正压力σ的关系符合库仑定律,但c,?值与一般土的抗剪强度指标的物理意义不同,还包含了根系的作用效果,在复合体含水量与正压力相同情况下,抗剪强度与含根量呈指数函数关系,根系总量增加,c,?值均呈增加趋势,显著提高了复合体抗剪强度,在复合体的含根量与正压力相同的情况下,抗剪强度与含水量呈幂函数关系,含水量的增加使c,?值减小,复合体抗剪强度降低;坡面岩体–基质–根系互作的力学特性具有明显的时间尺度效应,草种为狗芽根时,播种后5个月基本达到稳定。

Substrate-root system complex (SRSC) is the main functional part of the eco-engineering for rock slope protection. It is important content for eco-engineering mechanism exploration to evaluate the interactional characteristics of SRSC quantification ally by mechanics. This paper discusses the interactional mechanics characteristics of SRSC from experiment. The shear and tensile strength of SRSC and the shear strength between complex and rock are both studied; the relationship of shear and tensile strength and factors of root amount and water content are also researched; the effects of time scale is discussed in the end. The results show that the shear resistance between SRSC and rock consists of friction and biotic force. The shear strength decreases with water content increasing while reduces with root amount increasing. They represent logarithm functional relationship. Water content influences on both friction and biotic force, but the latter is the main influenced aspect. The complex has tensile strength due to root system. The tensile strength increases with root amount enhancing while decreases with water content increasing. They represent relatively notable functional relationship. The reinforced effect and friction enhance with root amount increasing, whereas reduce with water content increasing. The relationship between shear strength (τ) and vertical pressure (σ) accords to Coulomb law. Besides general physical significance of shear strength indexes, φ and c include the effect of root system. In the case of the same water content and vertical pressure, shear strength and root amount represent exponential functional relationship. The values of φ and c increase with the total amount of root system enhancing. So the shear strength of complex will be elevated markedly. In the case of the same root amount and vertical pressure, shear strength and water content represent power functional relationship. The values of φ and c decrease with water content enhancing. So the shear strength of complex will decline. The interactional mechanical characteristics of the rock-substrate-root system exhibit a significant time scale effect with plant developing, and it gets stable after 5 months of seeding when Cynodon dactylon is concerned. It is an essential support to renew the theory of the eco-engineering for rock slope protection and to apply it.