水泥砂浆水力劈裂试验研究

选用水泥砂浆作为试验材料,研究其在水力劈裂条件下的破坏特征。制作空心圆柱试件,在三轴渗流应力耦合试验仪上进行水力劈裂破坏试验,得到试件破坏时的应力状态没有满足整体的破坏条件。对此做了详细研究,认为之所以出现这种情况是因为材料不均匀。材料的不均匀引起了试件内部应力场分布不均匀。在处于高应力的某些点上,首先达到破坏条件(拉剪破坏条件),出现微裂纹。微裂纹出现以后,应力集中显著,微裂纹沿裂尖继续扩展,直到整体劈裂,试件破坏。文中建议用材料非均匀系数描述这种非均质材料的破坏特性。非均质系数越大,材料发生低应力状态破坏的可能性越大。

HYDRAULIC FRACTURE TEST ON CEMENT AND SAND MORTAR

Hollow columns were made with sand-cement grout as test samples,on which the failure characteristic was studied in the condition of tri axis hydraulic fracturing.The samples were tested on tri axis seepage-stress coupled test apparatus.The data from test show that the stress states did not meet the failure criterion when samples failure.That phenomenon was studied in detail.The result that it was the asymmetry of the sample material leads to the stress field asymmetry.And local high stress can make sample failure from the local spot.Then stress concerctration happened in the failure spot,which focused on the fracture tip.And then the fracture development was induced.Finally the sample damaged entirely.A new concept,inhomogeneous coefficient,was set up to be used to describe the phenomenon of brittle materials failure in low stress level.For any brittle materials,the larger the inhomogeneous coefficient is,the larger the possibility of failure in low stress level is.