12th ISRM Congress

ABSTRACT: Drilling and blasting are two necessary stages in mining engineering and construction works. Although drilling and blasting prove useful, have a few detrimental impact on structures located at the neighboring township and residential spots. To name a few, these problems are fly rock, air blast, back break and ground vibration. Amongst all problems originated in blasting, because of stringent statutory regulations blasting induced ground vibration can lead into early mine closure. To measure ground vibration intensity in a blasting site, peak particle velocity is globally accepted in literature as a criterion. Developed by some researchers, a number of empirical equations are applied to predict peak particle velocity prior to blasting. Application of these equations is limited to presence of observed field blasting parameters including value of charge per delay and distance of measurement point from the center of charge. Although the results of predictions are roughly acceptable, studies are being conducted to improve these results using soft computing methods up to a satisfactory level. In the present study Genetic Programming (GP) was used to find an unknown function to predict peak particle velocity. When compared to the observed peak particle velocity, GP P obtained equation presents better results than empirical equations.

ABSTRACT: The basic friction angle is a fundamental parameter of intact rock that contributes largely to the strength of rock fills. It is a key parameters of the Barton and Kjaernsli model for rock fills. Experimental difficulties encountered when measuring the basic friction of a very strong meta-sandstone with the help of a Golder shear box are described. Values measured on diamond saw cut surfaces are very low and reflect the quality of cutting rather than the natural rock texture. Values measured on sand blasted surfaces are low as sand blasting caused micro-damage to the rock surface. Values measured on rough tensile cracks after correction for dilatancy are high and higher than 40° which seems to be a upper bound for the basic friction angle of silicate rocks, based on results published in the literature. Such high values are explained by the very tight interlocking and very high strength of the small scale surface asperities.

ABSTRACT: Drying-induced deformations of porous materials are ubiquitous phenomena, but coupled behaviors of deformation and moisture distribution inside the material. In this paper, we introduce drying-induced deformation behaviors of sedimentary rocks which have been obtained in our laboratory, and the maximum volumetric shrinkage in each rock type is compared with its first- and second-peak radius of pore size distribution from mercury intrusion porosimetry, which represents pore structure, so that a maximum volumetric shrinkage of a rock can be estimated by a simple method. As a result, maximum shrinkage strain is thought to depend on existence of smaller pore size and both quantities are plotted on right upper portion bounded by a line of the log-log graph. That is, rock with smaller peak radius is more shrinkable.

ABSTRACT: Blast induced vibration is one of the most important environmental problems in various sectors such as mining, quarry, tunneling and pipeline trenching. Therefore, experts in this field study intensively to eliminate these effects. The majority of these studies focus on the generation of equations for forecasting values of blast induced vibrations. However, experts do not seem to have reached a consensus on the issue of forecasting and preventing blast induced vibration. This can be explained by ground conditions and design parameters that are totally different from each other. In this study, for the purpose of determining estimation performances of 11 equations suggested in literature for blast induced vibration, 93 blasts from 3 panels in Seyitömer Coal Mine in Turkey were observed and they were assessed on the basis of these methods and the method with the highest correlation value was determined.

ABSTRACT: When a tunnel is constructed in squeezing rocks, it is important to close a tunnel cross section early to minimize deformation. However, it is not easy to select an appropriate supporting scale and closure timing depending on the condition of rock mass. This paper considers a case of the Nanao tunnel in which the supporting scale and closure timing were determined according to measurement results obtained during the course of tunnel construction. In addition, this paper demonstrates influences of the difference in tunnel closure timing on the surrounding by using a three-dimensional numerical analysis. As a result, in the case of the Nanao tunnel, an appropriate supporting scale and closure timing were selected and a smooth tunnel construction was achieved. The numerical analysis also verified that the early closure of the cross section was effective.

ABSTRACT: The multi-parameter measurement system involves electric potential (EP) variations, electrical resistivity, acoustic emissions (AE), rock temperature (RT), acceleration in addition to the conventional displacement (strain) and load (stress) measurements. This study is concerned with the multi-parameter response of soft rocks during deformation and fracturing process. Some of experiments were carried out under purely mechanical manual loading without using the loading device, which may utilize AC current as power source. Therefore, the loading system is free of electric noise, which may be caused by the loading system. The authors present the outcomes of these experiments and discuss of the implications of multi-parameter response in geomechanics and geoengineering.

ABSTRACT: Parallel deformability tests: three rigid Plate Loading (PLT) and one extra Large Flat Jack (LFJ) were performed side by side in slightly jointed marlstone in order to compare their results. Pressure-displacement data obtained from LFJ and PLT tests are presented and processed using different formulas to determine overall (by the least-squares method), instant and interval moduli. Different moduli interpreted from PLTs are compared to moduli from the LFJ test data. The case shows typical problems encountered in PLT data interpretation.

ABSTRACT: Hydraulic fracturing is one of method to determine the in-situ stress,which can be done by analyzing the hydraulic pressure that could create a fracture on the borehole wall. One of the difficulty of the method is the packer system that isolate the interval test which should have design to overcome the pressure as high as the breakdown pressure in the interval test. The new method which conduct the test at the end of borehole, therefore the isolation is needed at one section had been studied at the laboratory. This research used three different nozzles to create various directions of fluid burst, which are vertical spray, horizontal spray (which is equivalent to the spray of packer) and a combination of vertical and horizontal spray. The effect from different types of nozzle to the result of hydraulic fracturing had been studied. This research tested hydraulic fracturing in three types of samples, which are concrete, limestone and andesite. The dimensions of those samples are (25 × 25 × 25) cm and cubical. Those samples were being subjected to triaxial loading during the hydraulic fracturing tests. Results showed that the most efficient type of nozzle that could initiate fracture in all of those samples is the nozzle that bursts a combination of vertical and horizontal spray.

ABSTRACT: The subsea tunnel with a length of 6.927 km between Boryung and Taean will be the first mined road tunnel in Korea. This tunnel, two-lane two tubes, has been planned to pass approximately maximum 60m under seabed and 80m under sea level. It is a drained tunnel under control of water ingress by grouting for watertight and is excavated by blasting. Project status is on the end of the detail design stage and construction will be started in the end of 2010. This paper intends to introduce some considerations about the secondary lining design considering the water inflow in the mined subsea tunnel. Firstly it is introduced the design concept of the secondary lining considering the water inflow and the drained material characteristic. And, the combination of the rock loads and residual water pressure is studied and proposed.

ABSTRACT: 95 abandoned old roadways up to 50 years old and 300m deep were observed at Kushiro Coal Mine. Large plastic deformations as roof deflection and/or floor heave closed most roadways although a few roadways were remain open. Such in-situ measurements as Rayleigh wave velocity, permeability etc. were carried out. Rayleigh wave velocity in the closed roadway was approx. half the virgin rock mass. Permeability of closed roadway was 40 times greater than that for virgin rock mass. This suggests that 1/40 sealability can be expected even a rock cavern in clastic rocks completely collapsed. This would be much better than rock cavern in crystalline rocks in which much less sealability is expected when completely collapsed.