岩石动静态参数间关系的研究

Relation between static and dynamic parameters of rocks

岩石由矿物颗粒组成,内部存在弱面、裂隙等结构,并非线弹性材料,动静态参数之间并没有确定的力学关系.含有大量裂隙的砂岩、煤等软弱岩石,动态模量大于平均模量;大理岩的动态模量大于变形模量,但与平均模量的关系较为复杂;火成岩及其变质岩,动态模量可以小于变形模量.动态泊松比对波速极端敏感,与静态参数没有明确的关系.现场取回岩块已经卸载、脱水,岩样加工也会对材料产生损伤,内部出现张开裂隙,超声波速度降低.如某大理岩矿岩墙端头所测纵波速度的平均值就大于室内岩样纵波速度的最大值,因而以岩体与岩样纵波速度的比值评价岩体完整性将偏于不安全.

Rock is made of mineral grains with fissures and cracks and it is not nonlinear elastic at all.There is no mechanical relation between the dynamic and static parameters.For weak rock with plenty of fissures such as sandstone and coal,the dynamic modulus is larger than the average modulus.However,for marble rock with different grains,the relation between the dynamic modulus and the average modulus is much complex although the dynamic modulus is larger than the deformation modulus.The dynamic modulus is even smaller than the deformation modulus for the volcanic or metamorphic rock.The dynamic Poisson's ratio is very sensitive to the wave speed and no clear pertinence with the static parameter.Rock blocks from in?situ have unloaded and dehydrated,and the machining of specimens may produce new damage.There are opening fissures in the specimen,which results in the supersonic wave speed lower.For example the average value of longitudinal speeds measured in the dike ends of one marble mine is larger than the maximum speeds of specimens.Therefore,it is not safe to evaluate the integrality of rock mass by the ratio of the supersonic wave speed in rock mass to that in the specimen.