Harushige Kusumi

Study on new formulation of shear strength for irregular rock joints

Abstract As is known, Ladanyis shear strength criterion is only applied to the regular triangular joints. The purpose of this study is the proposal of a new shear strength criterion which is applied to irregular joints. First of all, the appropriate estimation method of irregular joint profiles must be quantitatively estimated. The artificial plaster specimens which have four different JRC profiles, and the sandstone specimens including the irregular joint are applied on the direct shear test. The other hand, before direct shear test, in order to estimate the irregular joint surface profile of these specimens, the measurement and analysis of joint surface profile for each specimen using laser profilometer have conducted. As the results, the new experimental equations which exactly represent the shear strength parameters included in Ladanyis shear strength criterion was proposed, and it is recognized that this new experimental equations can be applied for the rock specimens having the irregular joint.

Seismic imaging ahead of tunnel face with three component geophones

Summary The present paper proposes an accurate imaging technique for looking ahead of tunnel face using three-component geophones with tunnel blasting and TBM vibrations as seismic sources. Its procedure is as follows: 1) Using three-component receivers set on the tunnel walls, record the seismic signal from the reflectors ahead of the tunnel face; 2) Detect the direction of incidence of the reflected wave; and 3) By weighting according to the direction of incidence of the reflected wave, image the reflector planes using the equi-travel time plane. The proposed technique is applied to datasets collected at an actual drilling operation site, and the results agreed with the geological observation of the walls after the drilling of the tunnel.

Imaging of Refracted Waves by Convolution

Summary Refraction seismology has a long history in obtaining estimates of subsurface structures. Among the many methods developed for the refracted waves the reciprocal method is the most popular. However, the application of the reciprocal and most other methods depends initially on picking the first arrival times. In this paper, we discuss a method for imaging refraction interfaces by using a convolutional method that does not require picking first break times. This avoids both the time-consuming first break picking and the possibility of erroneous picks. We use the analogy of convolution to the summation of time delays and correlation to differences of time delays. Therefore, the reciprocal method can be performed as a convolution of the initial arrival portion of the forward and reverse profile traces and a correlation of the travel time between forward and reverse source positions. With the elimination of picking, the proposed method may be more productive than graphical procedures. However, convolutions produce more ringing than the original records, so it is necessary to apply some data processing procedures before using the proposed method. We present the theoretical background of the convolutional method and its application to synthetic and field data.

On measuring settlement by magnetic method at any depth

Abstract When artificial islands are constructed, they are subject to surface subsidence, which is the resultant sum of the consolidation strata, many of which seem differ in character. When these strata are soft and thick, or heavily loaded, it becomes very difficult to estimate how much settlement will eventually take place, and over how long a period. For the estimate to be accurate, the settlement characteristics of each layer must first be determined. For this purpose, the authors have investigated a new method of measuring settlement, based on two unique principles. One principle is the application of a permanent magnet as an indicator of settlement, and the other is the exploitation of semiconductor, magneto‐resistance elements for detecting the magnetic fields. In advance of the observation, the magnets are forced into the earth, being pushed out through the bore‐hole casing by the oil jack at suitable depths and intervals. The small‐sized magneto‐resistance element is essential to the practicalit...

A Trial About the Evaluation of Compound Geophysical Explorations by Self-Organizing Maps

In Japan, in the high economic growth period in 1960’s, a great number of slopes were formed to construct many roads. Now, the slopes have been aging, it is important to estimate the health of the aging slope and maintain slopes effectually. So, in situs, we usually carry out seismic wave method, surface wave method, electric method, electromagnetic wave method, frequency domain electromagnetic method and so on. However, there is not the technique to compound and interpret the result of each geophysical exploration in a numerical formula of the engineering now. Therefore, we notice to self-organizing maps (SOM) used widely in a field of the information processing engineering, and tried to interpret multidimensional data by integrating. In this paper, we classified the ground property by self-organizing maps. The classification result is relatively conformal with boring data. Therefore, it is recognized that it can be used to improve the interpretative accuracy of compound geophysical explorations. And, it can be shown that this technique is effective to estimate of the ground property of the aging slope.

True Tri-Axial Test Using Distinct Element Method

Many kinds of rock test for engineering properties have been carried out to obtain rock kinetic properties. However it is difficult to visualize inside rock specimen during laboratory tests. This studys objective is to reconstruct true tri-axial tests using Distinct Element Method (DEM). At first, tri-axial compression test is carried out to know correlations between analytical properties and rock properties obtained through compression test like cohesion and internal friction angle. Next, true tri-axial test is simulated using properties above. The result of the simulation, it was clarified that the simulation result can reconstruct a laboratory test qualitatively.

DEVELOPMENT OF MONITORING SYSTEMS FOR ROCK SLOPE BY OPTICAL STRAIN SENSOR

岩盤斜面の動態観測に関しては, 1996年に起こった北海道豊浜トンネル岩盤崩落事故を契機として, 岩盤斜面の計測監視技術の確立が大きな問題となっている. 本研究は, 光ファイバセンサによって自然もしくは人工的な岩盤斜面の動態観測手法として, 実際の現揚計測に適用することを想定し, 引張・田縮ひずみを捉えるための固定方法を検討し, その固定方法における種々の確認試験を実施させた. その結果を基に, 実際の亀裂性岩盤斜面において, 光ファイバセンサをV宇型に敷設させた. そして, 岩盤斜面内に静的破砕剤を注入することにより, 人工的に岩盤亀裂を変位させ, そのときの光ファイバセンサの出力特性について検討した. さらに, 人工的に変位させた箇所については, 光ファイバセンサと平行に変位計を取り付けることにより光ファイバセンサの有用性が認められた.

Application of Continuous Failure State Direct Shear Test on Discontinuous Rocks.

In the determination of the shear strength of rocks, a lot of similar specimens are needed to obtain satisfactory results, but the preparation of the specimens of same characters involves great difficulties, especially in the case of discontinuous rocks. It is desirable if the strength envelopes could be obtained from only one specimen.In this study, we carried out two types of CFS tests, and a series of constant stress shear tests for plaster specimens with regular triangular joint. In addition to these tests, we carried out multi-stage shear tests for rock specimens with artificially generated irregular joint. We made comparison of the results obtained by these tests, and examined the applicability of CFS tests.

A development of settlement measuring system using magnetic sensor and it's application.

The new method of measuring settlement using one bore hole which has enable the increase of measuring points during observation were developed. The principle of this method is based on two unique points, one of which is application of a permanent magnet as an indicator of settlement, and the other is the exploitation of semi-conductor magneto-resistance elements for detecting the magnetic fields. In advance of the observation, the magnets are forced into the earth penetrating the VINYL CHLORIDE casing of bore hole by the oil jack at suitable depths and intervals, and the small sized magneto-resistance element is much use of realization of this idea.In this paper, the principles of this method, measuring procedure, the special characteristics and potential of this system and the results of field trials are described.