公路高陡边坡含软弱层灰岩的劣化特性研究

Research on Deterioration Characteristics of Limestone with Weak Layer in High-steep Slope of Highway

奥陶系灰岩具有成岩作用好、强度高、脆性大的特点。而岩体由于其特殊的形成条件,在岩体中存在大量的矿脉结构,易受风化作用的影响;同时,节理发育也会导致岩体劣化。以太行山奥陶系灰岩为研究对象,进行了室内干湿交替试验,得到了石灰石的劣化特征,建立了波速与空隙之间的数学模型。研究表明:(1)岩样声波波速在干湿交替过程中逐渐减小,并且横波比纵波的变化更为明显,由此说明灰岩的剪切特性发生较强的劣化;(2)试验中存在3种不同的劣化形式,即原生裂纹发育、矿脉延伸和表面剥蚀,在研究中以矿脉延伸为主要劣化形式;(3)矿脉劣化主要表现为颗粒脱落和空隙延伸,减弱了声信号能量的耗散;(4)利用大开空隙率、抗拉强度和点荷载强度建立了灰岩的劣化模型,可见其呈“S”型增长(减小)。

Ordovician limestone is featured with good diagenesis, high strength and brittleness. Due to its special formation conditions, the rock mass has a large number of vein structures, which are susceptible to weathering. At the same time, the development of joints will also cause the rock mass to deteriorate. Taking the Ordovician limestone of Taihang Mountain as the research object, the indoor dry-wet alternate tests are carried out, the degradation characteristics of limestone are obtained, and the mathematical model between wave velocity and gap is established. The studies show that:(1) The wave velocity of the rock sample gradually decreases in the process of dry and wet alternate, and the change of shear wave is more obvious than that of longitudinal wave, which indicates that the shear characteristics of limestone have been strongly degraded;(2) Three are three different forms of deterioration in the test: primary crack development, vein extension and surface denudation. In this research, vein extension is the main form of deterioration;(3) The vein deterioration is mainly manifested as particle shedding and void extension, which reduces the dissipation of acoustic signal energy;And(4) a degradation model of limestone is established through large open void ratio, tensile strength and the point load strength, showing an “S”-shaped increase(decrease).