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ABSTRACT: Joint lineal density is one of the most important joint characteristic elements which describes rock mass properties such as deformability, permeability and so on. This paper suggests joint lineal density diagram in order to describes the joint lineal density measured in the arbitary direction and permeability anistropy diagram in order to describe permeability anistropy of the jointed rock masses estimated in the arbitary direction. 1. INTRODUCTION Stereographic projection has been used as a graphic device for solving geological problem. For instance, we often use it to grasp the orientational distribution of discontinuities in rock masses. It also has been applied to examine stability of a rock slope and underground excavern by Hoek and Bray¹) and Hoek and Brown), respectively and also plays important role in Key Block analysis which is suggested by Goodman and Shi). Since the mechanical and hydraulic behaviour of jointed rock mass are strongly affected by joint distribution, we have to grasp rock masses anisotropy in order to improve rock masses using grouting technique or reinforce rock masses using Rockbolt and/or anchor effectively. Although it is important subject to grasp it, stereographic projection has not been used to describe rock masses anisotropy directly. So the authors suggest new graphic device in order to express the anisotropy of rock masses by stereographic projection. In this paper the authors suggest Joint lineal density diagram and anisotropic permeability diagram which give us an effective information when we attempt to reinforce or improve joints effectively. 2. ESTIMATION OF JOINT ORIENTATION DISTRIBUTION Before referring to JLD diagram and JP diagram the estimation for joint orientation distribution is examined. Since a lot of joints exist in the objective foundation, it is necessary to estimate joint orientation distribution statistically. 2.1 Correction for sampling biases Joint sampled population usually has sampling biases because joint information that we can obtain from the site, differs with the method of the survey. Scanline or Scanwindow survey is often used in order to sample joint data. Joint orientation distribution which is estimated from the field data directly, usually differ from the genuine distribution in rock masses because of the sampling biases. Therefore it is necessary to remove or minimize these biases caused by each sampling method. Statistically, each sample should not be dealt with equally, but have to be weighted according to the probability of its sampling. As the method to estimate the genuine orientation distrinution of joints, spherical net can be used to calculate the orientation density which is the probability density of orientation distribution. The orientation density is measured at each measuring pole which are established at interval of η=. The coordination of measuring pole is given by zenithal angle θ= and argument angle = in polar coordinate. The measuring pole must be located at a certain interval in order to measuring the density homogeniously on the sphere. It is difficult to established the point at a certain interval on the sphere. Using the following equation, However, we can obtain the location of the point which is homogenious for the engineering purpose on the sphere. 3. JOINT LINEAL DENSITY DIAGRAM (JLD DIAGRAM) Joint lineal density is defined as the number of joints per unit length that appear on the scanline, and has been applied to the design and construction of the civil engineering structure in various way. For instance, joint mean spacing, which is a reciprocal number of joint lineal density, has been used for a principal element of some notable rock classification methods.
ABSTRACT: A test system using "Rock Test Hammer" is often used to evaluate rock mass properties, simply. The Strike Response Value is measured by using this machine, and the modulus of elasticity is expected. So, in order to apply this principle to the borehole investigation, we develop a new machine "Borehole Hammer"(Figure 1). With regard to this machine, the laboratry testing using rock specimen was carried out and we have a successful results. However, in-situ testing has hardly been made. So we made the in-situ testings using "Borehole Hammer" and borehole expansion tests in order to grasp the applicability of "Borehole Hammer". As the results, the relationship between strike response value obtained by "Borehole Hammer" and elasticity tends to linear and the applicability of "Borehole Hammer" to the in-situ rock masses is clarified at this test yard. 1. INTRODUCTION In the case that we examine the foundation a civil engineering construction, it is necessary to grasp the engineering property. These values are obtained by many kinds of in-situ rock tests such as plate bearing test and in-situ shearing test, but these tests are so expensive that we cannot make enough tests to estimate the rock mass properties of the objective region for design. Because of these situations, we have desired the establishment of easier and cheaper in-situ rock test system. A test system using "Rock Test Hammer" is often used to evaluate rock mass properties, simply. Strike response value is measured by using this machine, and the modulus of elasticity is expected. So, in order to apply this principle to the borehole investigation, we develop a new machine "Borehole Hammer"(Figure. 1). With regard to the this machine, the laboratry testing using rock specimen was carried out and we have a successful results. ¹) However, in-situ testing has hardly been made. This paper introduces the outline of the Borehole Hammer and describes the methods and the results of the in-situ testing by the use of this hammer. 2. OUTLINE OF BOREHOLE HAMMER The Borehole hammer is broadly divided the insertion part into the borehole (sonde part) and the data collection part. The external appearance of this hammer is shown in Figure 1. 2.1 Sonde part The sonde part consists of the hammer part which strikes the borehole wall, the reception part which receives elastic waves that hae been generated by the strike, and the fixing unit which presses the sonde against the borehole wall before the striking test. The Strike Response Value is measured by the hammer part. In order to obtain the more accute Strike Response Value, it is desirable that strike energy is constant. As the result, a hammer has been conceived which has a construction of driving it by elctro-magnetic forces as shown in Figure 2. Using this mechanism, it has become possible to strike the borehole wall at constant striking forces regardless of whether or not there is water in the borehole. The reception parts are installed at two locations consisting of velocity sensor. At the rear of the sensor, a spring is fitted to improve its contant to the borehole wall. For the fixation unit, a system of the two rigid arms which can be opened and be closed by motor driving has been adopted. The fixing devices have been installed, one at top of the sonde, and the other at its bottom, this sonde can be used for the borehole with a diameter of about 56 to 76 mm. 2.2 Data recording device The data recording device consists of measuring unit CRT display, printer and recorder. These component units are encased in a single accommodating body.