The hydromechanical properties of single self-propping fractures under stress are of fundamental interest for fractured-rock hydrology and a large number of geotechnical applications. This experimental study investigates fracture closure and hydraulic aperture changes of displaced tensile fractures, aligned tensile fractures, and saw-cut fractures for two types of sandstone (i.e., Flechtinger and Fontainebleau) with contrasting mechanical properties, cycling confining pressure between 5 and 30 MPa. Emphasis is placed on how surface roughness, fracture wall offset, and the mechanical properties of the contact asperities affect the self-propping potential of these fractures under normal stress. A relative fracture wall displacement can significantly increase fracture aperture and hydraulic conductivity, but the degree of increase strongly depends on the fracture surface roughness. For smooth fractures, surface roughness remains scale-independent as long as the fracture area is larger than a roll-off wavelength and thus any further displacement does not affect fracture aperture. For rough tensile fractures, these are self-affine over a larger scale so that an incremental fracture wall offset likely leads to an increase in fracture aperture. X-ray microtomography of the fractures indicates that the contact area ratio of the tensile fractures after the confining pressure cycle inversely correlates with the fracture wall offset yielding values in the range of about 3–25%, depending, first, on the respective surface roughness and, second, on the strength of the asperities in contact. Moreover, the contact asperities mainly occur isolated and tend to be preferentially oriented in the direction perpendicular to the fracture wall displacement which, in turn, may induce flow anisotropy. This, overall, implies that relatively harder sedimentary rocks have a higher self-propping potential for sustainable fluid flow through fractures in comparison to relatively soft rocks when specific conditions regarding surface roughness and fracture wall offset are met.

应力作用下的单个自支撑裂缝的流体力学特性对于裂隙岩石水文学和大量的岩土工程应用具有根本的意义。这项实验研究调查了两种类型的砂岩（即，Flechtinger和Fontainebleau）的位移拉张裂缝，对准拉张裂缝和锯切裂缝的裂缝闭合和水力孔径变化，其力学性能不同，循环围压在5 MPa至30 MPa之间。重点放在表面粗糙度，裂缝壁偏移以及接触粗糙结构的机械性能如何影响法向应力下这些裂缝的自支撑潜力上。相对的裂缝壁位移会显着增加裂缝孔径和水力传导率，但是增加的程度在很大程度上取决于断口的表面粗糙度。对于光滑的裂缝，只要裂缝面积大于滚降波长，表面粗糙度就与尺寸无关，因此任何进一步的位移都不会影响裂缝的孔径。对于粗大的拉伸裂缝，这些裂缝在较大范围内是自仿射的，因此增加的裂缝壁偏移可能会导致裂缝孔径的增加。裂缝的X射线显微照片表明，在密闭压力循环后，拉伸裂缝的接触面积比与裂缝壁偏移屈服值成反比，该值大约在3％至25％的范围内，首先取决于相应的表面粗糙度第二，接触粗糙的强度。而且，接触粗糙主要发生在孤立的地方，并且倾向于优先在垂直于裂缝壁位移的方向上取向，这反过来又可能引起流动各向异性。总的来说，这意味着当满足有关表面粗糙度和裂缝壁偏移的特定条件时，与相对较软的岩石相比，相对较硬的沉积岩石具有较高的自支撑潜力，使流体可持续流过裂缝。