摘要
基于热力学原理，油松比允许范围为－１≤σ≤０．５。虽然具有负泊松比的物质在理论上是存在的，但是除密度泡沫材料外，具有负泊松比的物质没有被发现．当岩石纵波速度与横波速度之比＜，则泊松比为负值。它揭示了岩石破碎的深层次问题，促使人们对能引导宏观观察负油松比效应的微观结构去探索，即从矿物、岩石的微观结构去探讨岩石破碎问题。这对深部地质钻探和深部地质理论也是一项必须探索的课题。
linear elastic isotropic material under any set of deformation, based on thermodynamicconsiderations of strain energy in the theory of elasticity, must remain positive, and results inwell - known allowable range of Poisson's ratio form - 1. 0 to + 0. 5. Materials exhibiting anegative Poisson's ratios are theoretically permissible, but such negative values have not beenfound for any isotropic materials. (A. E. H. Love, 1927).Materials with negative Poisson's ratios have been continuously discovered, since then andsuch negative values might be caused by a twinned crystal, phase change of quartz or variousamounts of microcracks.Special observation was made by the authors on q simple unconfined compression test of 3schist, 3 siltstone and 1 marble cores affirmatively with V,/V,M N, which gave negativePoisson's ratio. On the material testing machine, an initial compression made every core reduced in diameter and the lower part of each resultant lateral strain curve 4 was negative. Nevertheless, there final Poisson's ratios were still positive.As regards rock fragmentation, 7 cores all showed shear failure. It is worth attention.The experiment showed that these rocks were of a high degree of anisotropy. They mustcontain obvious microcracks and cracks as well as oriented crystals of muscovite. At lowerstresses, while the cracks are closed and minerals therein are extruded, void space in the coreswith the edges of broken void spaces will be created. With increase of the compression, partialvoid spaces collapse, diameter of core contracts and hence, negative Poisson's ratio appears. Athigher stresses,as void spaces are filled up, the final Poisson's ratios are still positive. Thenegative Poisson's ratios only occur in some directions and may be dominated by coupling between stretching force and shear deformation. Shear failure of all 7 cores is in accordance withthe above - mentioned analysis.However, R. Lakes produced a new material with negative Poisson's ratio in 1987, which,by contrast, needs not be anisotropy. The ph
出处
《探矿工程》
1996年第4期17-19,共3页
Exploration Engineering(Drilling & Tunneling)
关键词
岩石
泊松比
微观结构
岩石破碎
rock longitudinal wave speed transversal wave speed Poisson's ratio micro - structure
