• Economic and Environmental Geology
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• v.50 no.1
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• pp.61-71
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• 2017

The effects of joint density and size distribution on the hydrogeologic characteristics of jointed rock masses are addressed through numerical experiments based on the 2-D DFN (discrete fracture network) fluid flow analysis. Using two joint sets, a total of 51 2-D joint network system were generated with various joint density and size distribution. Twelve fluid flow directions were chosen every $30^{\circ}$ starting at $0^{\circ}$, and total of 612 $20m{\times}20m$ DFN blocks were prepared to calculate the directional block conductivity. Also, the theoretical block conductivity, principal conductivity tensor and average block conductivity for each generated joint network system were determined. The directional block conductivity and chance for the equivalent continuum behavior of the 2-D DFN system were found to increase with the increase of joint density or size distribution. However, the anisotropy of block hydraulic conductivity increases with the increase of density discrepancy between the joint sets, and the chance for the equivalent continuum behavior were found to decrease. The smaller the intersection angle of the two joint sets, the more the equivalent continuum behavior were affected by the change of joint density and size distribution. Even though the intersection angle is small enough that it is difficult to have equivalent continuum behavior, the chance for anisotropic equivalent continuum behavior increases as joint density or size distribution increases.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.368-376
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• 1999

This paper predicts the changes in the spring constant, the resonant frequency, the electrostatic force, and the displacement of a resonant structure due to non-ideal anisotropic RIE etching process. First, a $6\;{\mu}m$ thick polysilicon was etched by RIE and the anisotropy of the etched structure was measured as a function of a RF power, a $Cl_2$ flow rate and a chamber pressure. In the experimental results, an anisotropy was decreased as the RF power, the $Cl_2$ flow rate, or the chamber pressure was increased. A comb actuator's operation characteristic was predicted depending on the anisotropy variations in RIE etching. Comb actuators with three different support beam structures were investigated : fixed-fixed, crab-leg, and double crab-leg. As the RIE etch anisotropy becomes non-ideal, i.e. the cross section becomes rather a trapezoidal than a rectangular shape, it decreases spring constant, resonant frequency and electrostatic force of a comb actuator but it increases the displacement of the mass. Among the three structures, the comb actuator with double crab-leg support beams is more influenced by anisotropy variation in RIE etch than other two.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.113-132
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• 1999

Recently in Korea, application of the soil nailing is gradually extended to the sites of excavations and slopes having various ground conditions and field characteristics. Design of the soil nailing is generally carried out in two steps, The First step is to examine the minimum safety factor against a sliding of the reinforced nailed-soil mass based on the limit equilibrium approach, and the second step is to check the maximum displacement expected to occur at facing using the numerical analysis technique. However, design parameters related to the soil nailing system are so various that a reliable design method considering interrelationships between these design parameters is continuously necessary. Additionally, taking into account the anisotropic characteristics of in-situ grounds, disturbances in collecting the soil samples and errors in measurements, a systematic analysis of the field measurement data as well as a rational technique of the optimum design is required to improve with respect to economical efficiency. As a part of these purposes, in the present study, a procedure for the optimum design of a soil nailing excavation wall system is proposed. Focusing on a minimization of the expenses in construction, the optimum design procedure is formulated based on the genetic algorithm. Neural network theory is further adopted in predicting the maximum horizontal displacement at a shotcrete facing. Using the proposed procedure, various effects of relevant design parameters are also analyzed. Finally, an optimized design section is compared with the existing design section at the excavation site being constructed, in order to verify a validity of the proposed procedure.