The results of theoretical and experimental studies of brittle and quasi-brittle fracture of plaster plates containing a circular hole and subjected to non-uniformly distributed compression are presented. This paper summarizes the results, partially published by the author earlier. To predict the critical load at the instant of crack initiation in case of quasi-brittle fracture with a developed process zone, it is proposed to modify the fracture criteria based on the theory of critical distances. The modified criteria contain a complex parameter which is associated with the fracture process zone and considers not only the material microstructure, but also the plastic properties of the material, the geometry of the specimen, and boundary conditions. Formulae are obtained for critical stresses in the problem of tensile crack initiation in a plate with a circular hole subjected to biaxial loading by tension along one axis and compression along the other axis. The deformation and fracture processes in brittle and quasi-brittle geomaterials under non-uniformly distributed compression are experimentally studied and the developed criteria are verified. In the first series of tests, the effect of the hole size on the initiation of tensile cracks at the hole under constant boundary conditions is described, and in the second series of tests, the effect of boundary conditions on the initiation of tensile cracks at the hole of fixed diameter is investigated. The results of the calculations are in good agreement with the experimental data. It is indicated by the results obtained that the developed TCD-based criteria properly describe the effect of both the hole size and the boundary conditions on the fracture of quasi-brittle material.

给出了具有圆孔并承受非均匀压缩的石膏板的脆性和准脆性断裂的理论和实验研究结果。本文对结果进行了总结，部分结果由作者先前发表。为了在工艺区域发达的准脆性断裂情况下预测裂纹萌生时的临界载荷，建议根据临界距离理论修改断裂准则。修改后的标准包含与断裂过程区域相关的复杂参数，不仅考虑材料的微观结构，而且考虑材料的塑性，试样的几何形状和边界条件。对于具有圆孔的板，通过沿一个轴的拉力和沿另一个轴的压应力承受双轴载荷，可以得出临界应力的公式，以解决拉伸裂纹引发的问题。对脆性和准脆性土工材料在非均匀分布压缩下的变形和断裂过程进行了实验研究，并验证了所建立的标准。在第一个系列的测试中，描述了孔尺寸对恒定边界条件下孔处拉伸裂纹萌生的影响，在第二个系列的测试中，边界条件对孔口处拉伸裂纹萌生的影响研究固定直径的孔。计算结果与实验数据吻合良好。