It is mainly caused by the ovalization of the cracked cross section and the changing of the lever-arm while the pipe is deformed when being bended.

试验表明，这是由于管道受载后，裂纹处管道截面变椭圆及由于管道弯曲变形导致加载过程中力臂的变化所引起。

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The failure of directly buried heat-supply pipeline is discussed, and the design essentials are put forward in accordance with local buckling and ovalization deformation.

探讨了直埋供热管道的失效，针对局部失稳和椭圆化变形，提出了设计要点。

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