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Kimoto, Kazushi*; Okano, Aoi*; Saito, Takayasu*; Sato, Tadanobu*; Matsui, Hiroya
Doboku Gakkai Rombunshu, A2 (Oyo Rikigaku) (Internet), 76(2), p.I_97 - I_108, 2020/00
This study investigates the propagation characteristics of surface wave traveling in a random heterogeneous medium. For this purpose, ultrasonic measurements are performed on a granite block as a typical randomly heterogeneous medium. In this measurement, a line-focus transducer is used to excite ultrasonic waves, whereas a laser Doppler vibrometer is used to pickup the ultrasonic motion on the surface of the granite block. The measured waveforms are analysed in the frequency domain to evaluate the travel-time for each measurement point based on the Fermat's principle. From the ensemble of travel-times, the probability distribution is established as a function of travel-distance. The uncertainty of the travel-time and its spatial evolution are then investigated using the standard deviation of the travel-time as a measure of the uncertainty. As a result, it was found that the uncertainty is approximately proportional to the mean travel-time divided by the square root travel-distance.
Inoue, Junya; Masumoto, Kiyoshi*
Doboku Gakkai Rombunshu, A2 (Oyo Rikigaku) (Internet), 74(2), p.I_55 - I_64, 2019/01
Saturated-unsaturated flow inversion program with adjoint method and least norm method was made to estimate saturated hydraulic conductivity and boundary conditions for multi-layers heterogeneous aquifer model. Vertical two dimensional numerical experiments assuming inclined ground consisting of three layers with different permeability were carried out using this program. Some inversion were carried out by changing the coefficient of least norm term to investigate the strength of constraints on the un-known parameters based on the reference value. The result show that it is possible to estimate the unique value of saturated hydraulic conductivity and boundary conditions for multi-layers heterogeneous aquifer model by the method.
Shimizu, Hiroyuki*; Koyama, Tomofumi*; Chijimatsu, Masakazu*; Fujita, Tomoo; Nakama, Shigeo
Doboku Gakkai Rombunshu, A2 (Oyo Rikigaku) (Internet), 68(2), p.I_477 - I_486, 2012/00
In this paper, the coupled thermal-mechanical processes in the 
sp
pillar stability experiments (APSE) were simulated using Distinct Element Method (DEM). By considering pre-existing cracks in the rock model, mechanical response of the rock during excavation phase and heating phase were successfully represented by DEM. Simulation results agree qualitatively well with the experimental results. However, the microcracks in the simulation were widely distributed around the heater and exfoliation of rock surfaces observed in the 
experiment was not formed accurately. To simulate more realistically the experimental results by the DEM models, the calibration of the microscopic parameters considering the model scale should be done. Moreover, more detailed discussion on the excavation damaged zone around the borehole and the distribution of pre-existing cracks are required.
