Most hydraulic aperture studies are based on rectangular flow system with linear shearing. This study investigates the influence of joint surface roughness on the hydraulic behavior, in the curved shearing surface or a circular joint. The most unique part of the investigation is the shape and configuration of the specimen, which is a set of concentric concrete samples. The hollow cylindrical cement mortars were used to duplicate natural rock joints. Various specimen roughnesses were used in the experiments to analyze the effect of roughness on joint hydraulic behavior. One side of the shearing plane rotated around a fixed axis and water, which flew through two shear planes in radial direction, was monitored. Experimental and numerical hydraulic apertures have been calculated by "Cubic law". The experimental hydraulic aperture has been calculated from laboratory flow rate measurement. The flow data were collected for every 0.5 second with slow angle velocity about 0.4 degree/min. This condition can be considered as stable transition of each asperity. Finite Element Method (FEM), numerical modeling, was used to estimate numerical hydraulic aperture from flow rate data by simulation of the given condition. To get input data for these flow rates, 3D roughness data was acquired from 3D laser profiling instrument. During the experiment, small load about 0.1 MPa was applied to shear surface to simulate vertical stress condition. Experimental and numerical results suggest that hydraulic apertures increase with increments of shear displacement. This result supports the condition that hydraulic apertures can be estimated from the roughness data in shearing mode.


Recent concern about Deep Underground Science and Engineering Laboratory (DUSEL) and nuclear depository has regenerated much interest in understanding of flow conditions in jointed rock. An important aspect of this topic is the evaluation of channel formation with integration of the mechanical properties and hydraulic properties of rock joint, since the hydro-mechanical behavior of rock joint can affect the whole underground structure and its stability. In underground construction, principle stresses might change its orientation due to excavation activities. Thus, rotary shear displacement may occur between blocks of a curved fracture. This scenario indicates that flow in the direction perpendicular to shearing direction can have significant effects on joint stability. However, most of hydro-mechanical experiments have been performed on one direction shearing which is parallel to flow direction. This is primarily due to difficulties involved with experimental work on curved fractures [1, 2, 3]. Only few experiments such as Cheon at el. [4] and Koyama et al [5] were performed on non-planar joints with rotational shearing mode. This study simulates flow through test in the direction perpendicular to shearing surface to evaluate the impact of surface roughness and hydraulic apertures. Working with roughness as a parameter has the benefit of being easily measured and reported in the field. Therefore one can estimate flow in different geometrical conditions. Hydraulic aperture can represent generalized flow rate regardless of the sample size and has been studied by others [6].

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