中文摘要：

断裂韧度和抗拉强度是岩石两个重要的力学特性。利用带切口的三点弯曲梁试验,研究了砂岩的断裂韧度和抗拉强度特性。对比和分析了带切口三点弯曲和巴西劈裂试验抗拉强度的差别。从理论和试验上,分析了目前常用的三种断裂韧度计算公式的差别。利用J积分理论计算了带切口的三点弯曲梁的断裂韧度K_（IC）。研究结果表明：相比于巴西劈裂试验,利用带切口的三点弯曲试验测得的抗拉强度更加稳定可靠;目前常用的三种断裂韧度计算公式在a/h较小时相差不大,但随着a/h的增大,差别越来越大,建议选用ASTM提出的公式;利用J积分计算得到的断裂韧度K_（IC）介于ASTM和Tada给出的公式计算结果之间,说明该方法是可靠的。

英文摘要：

The tensile strength and fracture toughness are two important mechanical parameters of rocks,which were studied using notched three point bending tests in this research.First,the tensile strengths of sandstone from notched three-point bending and Brazilian tests were compared.Then the differences of three popular formulas for fracture toughness were analyzed in both theory and laboratory test.Finally,a finite element method to determine the fracture toughness KIC using the J- integral was studied.The results indicate that compared with the Brazilian disc test,the tensile strengths of sandstone from notched three-point bending are more reliable.The three formulas for fracture toughness are almost equivalent.But the formula of ASTM is best.The fracture toughness of sandstone from J-integral is between that from ASTM and Tada,which demonstrates this method is applicable and should be used widely.