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Two chemical oxygen-type and one bottled oxygen-type self-contained self-rescuers were evaluated by a breathing simulator and a human subject. The metabolic rate in the simulator tests was equivalent to light work; the human subject tests were at a heavy work load. It was found that some self rescuers led to a rapid increase in inhaled carbon dioxide when the metabolic rate exceeded the absorbent capacity of the units. In those cases, the user could not continue breathing through the unit and walking. To ensure the safety of the user, it is proposed that the certification standards should include a test of carbon dioxide absorbence capacity under heavy work conditions., Two chemical oxygen-type and one bottled oxygen-type self-contained self-rescuers were evaluated by a breathing simulator and a human subject. The metabolic rate in the simulator tests was equivalent to light work; the human subject tests were at a heavy work load. It was found that some self rescuers led to a rapid increase in inhaled carbon dioxide when the metabolic rate exceeded the absorbent capacity of the units. In those cases, the user could not continue breathing through the unit and walking. To ensure the safety of the user, it is proposed that the certification standards should include a test of carbon dioxide absorbence capacity under heavy work conditions.

Several types of experiments and theoretical investigations were carried out. Model and full-scale experiments were conducted to clarify the behaviour of open fires. Studies were also conducted to obtain fundamental data on temperature distributions and the change in ventilation during the fire. Other experiments and numerical simulations established a guideline for fire spread suppression facilities such as fire break zones and water spray zones., Several types of experiments and theoretical investigations were carried out. Model and full-scale experiments were conducted to clarify the behaviour of open fires. Studies were also conducted to obtain fundamental data on temperature distributions and the change in ventilation during the fire. Other experiments and numerical simulations established a guideline for fire spread suppression facilities such as fire break zones and water spray zones.

From propagation experiments carried out at frequencies of 151.89 and 468.95 MHz along a gallery in an experimental coal mine, it was shown that higher frequncies exhibit better propagation properties, ie, the propagation loss becomes lower in cases of higher frequency range. This tendency was confirmed by theoretical numerical analysis. Propagation experiments at a frequency of 814.2MHz were carried out in galleries at the experimental coal mine and practical experiments were also carried out at the Takashima colliery at frequency bands of 150, 450 and 800 MHz as a preliminary test for the practical use of UHF radiowaves, in galleries with a large crossection. These tests were developed in order to determine the propagation properties of such frequencies in underground mines. Results obtained from these experiments are discussed., From propagation experiments carried out at frequencies of 151.89 and 468.95 MHz along a gallery in an experimental coal mine, it was shown that higher frequncies exhibit better propagation properties, ie, the propagation loss becomes lower in cases of higher frequency range. This tendency was confirmed by theoretical numerical analysis. Propagation experiments at a frequency of 814.2MHz were carried out in galleries at the experimental coal mine and practical experiments were also carried out at the Takashima colliery at frequency bands of 150, 450 and 800 MHz as a preliminary test for the practical use of UHF radiowaves, in galleries with a large crossection. These tests were developed in order to determine the propagation properties of such frequencies in underground mines. Results obtained from these experiments are discussed.

Oxygen self-rescuers remove exhaled CO2 with a chemical agent and augment O2 from a compressed or chemical store. Problems with evaluation methods in Japan include the measurement of dry-bulb temperature, lack of information about the effects on metabolism of hyperoxia (40% O2) and hypercapnia (3% CO2), lack of information about the effect on breathing rate of elevated CO2 during exercise, lack of information on the increase in breathing resistance as CO2 stimulates breathing, and failure to evaluate under heavy work. It is recommended that the limit for inhaled CO2 should be lowered from 3% to 2% and the limit for breathing resistance to plus or minus 500 Pa at 30 l/min. CO2 absorbent capacity should be tested under heavy work conditions., Oxygen self-rescuers remove exhaled CO2 with a chemical agent and augment O2 from a compressed or chemical store. Problems with evaluation methods in Japan include the measurement of dry-bulb temperature, lack of information about the effects on metabolism of hyperoxia (40% O2) and hypercapnia (3% CO2), lack of information about the effect on breathing rate of elevated CO2 during exercise, lack of information on the increase in breathing resistance as CO2 stimulates breathing, and failure to evaluate under heavy work. It is recommended that the limit for inhaled CO2 should be lowered from 3% to 2% and the limit for breathing resistance to plus or minus 500 Pa at 30 l/min. CO2 absorbent capacity should be tested under heavy work conditions.

Several cases have been reported of spontaneous combustion in underground anthracite coal mines in Vietnam, and preventive measures recommended have included the installation of sealing walls at all the intake and exhaust galleries to cut the air supply in those areas susceptible to spontaneous combustion. Gas samples were taken from inside the sealing walls at the Hong Thai, Trang Khe and Khanh Hoa mines and analysed using gas chromatography. The gases detected were CH4, CO, CO2 and H2, but no other hydrocarbon gases were found. Heating tests were conducted on coal samples weighing about 100 g with a particle size of less than 500 micrometres in a sealed cylindrical tube. The samples were obtained from Seam 24 at the Hong Thai mine, the Khanh Hoa mine and Seam 91 at the Enterprise mine, and tests were also carried out on a sub-bituminous coal from the Phan Me mine. The results confirmed those obtained from the site investigations. Only H2 and CO gases, together with trace CH4, were detected for the anthracite coals, with no hydrocarbon gases of C2 or above. The results show that the presence of H2 may be an important indicator for spontaneous combustion of anthracite coal., Several cases have been reported of spontaneous combustion in underground anthracite coal mines in Vietnam, and preventive measures recommended have included the installation of sealing walls at all the intake and exhaust galleries to cut the air supply in those areas susceptible to spontaneous combustion. Gas samples were taken from inside the sealing walls at the Hong Thai, Trang Khe and Khanh Hoa mines and analysed using gas chromatography. The gases detected were CH4, CO, CO2 and H2, but no other hydrocarbon gases were found. Heating tests were conducted on coal samples weighing about 100 g with a particle size of less than 500 micrometres in a sealed cylindrical tube. The samples were obtained from Seam 24 at the Hong Thai mine, the Khanh Hoa mine and Seam 91 at the Enterprise mine, and tests were also carried out on a sub-bituminous coal from the Phan Me mine. The results confirmed those obtained from the site investigations. Only H2 and CO gases, together with trace CH4, were detected for the anthracite coals, with no hydrocarbon gases of C2 or above. The results show that the presence of H2 may be an important indicator for spontaneous combustion of anthracite coal.

Vietnamese coal mines are facing an extraordinary expansion, forecast to increase production from 33 000 000 t in 2006 to 75 000 000 t in 2025 despite open-pit output decreasing to 12 000 000 t. The rapid deepening of many mines is exemplified by projected output from the different working levels at Mao Khe coal mine, resulting in an increase in average depth from 25.0 m in 2005 to a forecast 70.7 m in 2008 and 115.0 m by 2916. The mine safety record has generally been good, 15 accidents having claimed more than three lives each since 1995 of which 7 were gas explosions, 4 roof falls, 3 inundations and 1 a mine-car runaway, but the increasing depths make these and other threats serious considerations for future safety management: potential risks are outlined in relation to gas explosions, underground fire, spontaneous combustion, flooding, strata control and transport accidents., Vietnamese coal mines are facing an extraordinary expansion, forecast to increase production from 33 000 000 t in 2006 to 75 000 000 t in 2025 despite open-pit output decreasing to 12 000 000 t. The rapid deepening of many mines is exemplified by projected output from the different working levels at Mao Khe coal mine, resulting in an increase in average depth from 25.0 m in 2005 to a forecast 70.7 m in 2008 and 115.0 m by 2916. The mine safety record has generally been good, 15 accidents having claimed more than three lives each since 1995 of which 7 were gas explosions, 4 roof falls, 3 inundations and 1 a mine-car runaway, but the increasing depths make these and other threats serious considerations for future safety management: potential risks are outlined in relation to gas explosions, underground fire, spontaneous combustion, flooding, strata control and transport accidents.

A method of evaluating the detonation properties of explosives in boreholes using a resistance probe and lead plate has been established. Detonation was studied in open and confined conditions in a borehole. Detonation properties in delay blasting in multiple boreholes were also studied. It was found that water-gel explosives with an Al sensitiser were influenced the most by stable pressure conditions, and emulsion explosives the least. The safety of direct and indirect initiation methods were studied and a precise timed initiation method established. A precise detonation machine and a precise detonator were also developed. Smooth blasting using the precise detonation system was modelled using an acrylic resin plate and mortar block and it was seen that crack propagation could be controlled by interfering with the stress wave. Vibration and fly rock characteristics were also modelled using numerical simulation., A method of evaluating the detonation properties of explosives in boreholes using a resistance probe and lead plate has been established. Detonation was studied in open and confined conditions in a borehole. Detonation properties in delay blasting in multiple boreholes were also studied. It was found that water-gel explosives with an Al sensitiser were influenced the most by stable pressure conditions, and emulsion explosives the least. The safety of direct and indirect initiation methods were studied and a precise timed initiation method established. A precise detonation machine and a precise detonator were also developed. Smooth blasting using the precise detonation system was modelled using an acrylic resin plate and mortar block and it was seen that crack propagation could be controlled by interfering with the stress wave. Vibration and fly rock characteristics were also modelled using numerical simulation.

Peak particle velocity (PPV) of ground vibration induced by blasting has been used as a standard for evaluating structural damage. There has been much consideration as to whether the PPV standard is adequate for evaluating public environmental disturbances. The vibration level (VL) has been developed which allows for the feeling of the human body against the acceleration of vibration. If the relation between PPV and VL can be quantitatively clarified it will be possible to estimate PPV from VL and vice versa. The relation is complicated in the case of ground vibration induced by practical delayed blastings because of factors such as the frequency components and the shape of the wave form. A new method to calculate VL from the velocity wave form is discussed. The method was applied to measured waves caused by tunnel blasting and a new relation between PPV and VL was proposed., Peak particle velocity (PPV) of ground vibration induced by blasting has been used as a standard for evaluating structural damage. There has been much consideration as to whether the PPV standard is adequate for evaluating public environmental disturbances. The vibration level (VL) has been developed which allows for the feeling of the human body against the acceleration of vibration. If the relation between PPV and VL can be quantitatively clarified it will be possible to estimate PPV from VL and vice versa. The relation is complicated in the case of ground vibration induced by practical delayed blastings because of factors such as the frequency components and the shape of the wave form. A new method to calculate VL from the velocity wave form is discussed. The method was applied to measured waves caused by tunnel blasting and a new relation between PPV and VL was proposed.

A model of the heating and evaporation of water droplets in hot gases was used to analyse and clarify the effects of water spray coolers in practical conditions and to determine the requirements of water spray zones for fighting underground fires. The results showed good agreement with those obtained by fire experiments using a full-scale test gallery. The conclusions as to quantity of water required, spraying duration and total amount of water to be stored in situ have been adopted as fundamental guidelines for coal mines by the Industrial Location and Environmental Protection Bureau., A model of the heating and evaporation of water droplets in hot gases was used to analyse and clarify the effects of water spray coolers in practical conditions and to determine the requirements of water spray zones for fighting underground fires. The results showed good agreement with those obtained by fire experiments using a full-scale test gallery. The conclusions as to quantity of water required, spraying duration and total amount of water to be stored in situ have been adopted as fundamental guidelines for coal mines by the Industrial Location and Environmental Protection Bureau.

In order to prove the practical effect of a water spray zone on the spread of underground fire, a full-scale experiment was performed in a 400 m long test gallery with a cross section of 5.4 m2. A water spray method is effective when water droplets are sprayed uniformly in the gallery and the mean droplet diameter is less than 0.4 mm. The cooling effect of the water spray is discussed quantitatively including aspects such as heat transfer and ventilation. It is shown that the quantity of water required to suppress the spread of fire is proportional to the air velocity and the cross section of the gallery., In order to prove the practical effect of a water spray zone on the spread of underground fire, a full-scale experiment was performed in a 400 m long test gallery with a cross section of 5.4 m2. A water spray method is effective when water droplets are sprayed uniformly in the gallery and the mean droplet diameter is less than 0.4 mm. The cooling effect of the water spray is discussed quantitatively including aspects such as heat transfer and ventilation. It is shown that the quantity of water required to suppress the spread of fire is proportional to the air velocity and the cross section of the gallery.

In an attempt to improve the prediction of blast sound propagation, a new method has been developed based on a solution of sound wave theory and spectral analysis such as the Fourier transformation. Based on this new calculation method, control methods of frequency component and sound level of blast sound due to delay blasting have also been discussed., In an attempt to improve the prediction of blast sound propagation, a new method has been developed based on a solution of sound wave theory and spectral analysis such as the Fourier transformation. Based on this new calculation method, control methods of frequency component and sound level of blast sound due to delay blasting have also been discussed.

A series of fire experiments carried out, in order to clarify the suppression effect of underground open fires, by a method of ventillation control using a parachute-type air block system, in a full-scale test gallery with a cross section of 5.4 m2, is described. This air block system could be used at the upstream side of a fire and the parachute-type curtain, made of heat resistant material, seals off the fire area in short times., A series of fire experiments carried out, in order to clarify the suppression effect of underground open fires, by a method of ventillation control using a parachute-type air block system, in a full-scale test gallery with a cross section of 5.4 m2, is described. This air block system could be used at the upstream side of a fire and the parachute-type curtain, made of heat resistant material, seals off the fire area in short times.

When the timber is exposed to the ignition source emitting heat more than 780 kW/m3, the fire develops into the fuel-rich condition, expanding the fire zone to the maximum length where most oxygen is consumed. The fire spread rates and the fire zone lengths in the full scale gallery are both proportional to the air velocity. Types of timbering also influence the behaviour of fire. The fire temperatures in arch lined timbering are lower than those in three piece timber sets. Assuming that fuel and ventilation conditions are the same, the fire spread rate of the timber zone is proportional to the ratio of gallery dimension to timber dimension, and the fire zone length is proportional to the gallery dimension. A mathematical method for estimating the fire spread rate and the fire zone length of underground open fires is proposed., When the timber is exposed to the ignition source emitting heat more than 780 kW/m3, the fire develops into the fuel-rich condition, expanding the fire zone to the maximum length where most oxygen is consumed. The fire spread rates and the fire zone lengths in the full scale gallery are both proportional to the air velocity. Types of timbering also influence the behaviour of fire. The fire temperatures in arch lined timbering are lower than those in three piece timber sets. Assuming that fuel and ventilation conditions are the same, the fire spread rate of the timber zone is proportional to the ratio of gallery dimension to timber dimension, and the fire zone length is proportional to the gallery dimension. A mathematical method for estimating the fire spread rate and the fire zone length of underground open fires is proposed.

The higher frequency bands (greater than 500 MHz) were more effective for underground communication as there was a lower propagation loss. Reasonably good agreements were observed between the mathematical model, based on the geometrical image source method, and the experimental results., The higher frequency bands (greater than 500 MHz) were more effective for underground communication as there was a lower propagation loss. Reasonably good agreements were observed between the mathematical model, based on the geometrical image source method, and the experimental results.

The effect of the inclination of the gallery on the spread rate of the timber fire was quantitatively analysed for both upward and downward spread of fire. Buoyancy effects created by the fire in an inclined gallery contribute to reducing the pressure loss of ventilation in case of ascending ventilation and to increasing it in case of descending ventilation. A method is proposed for estimating the fire spread rate and the fire zone length, taking the variation of ventilation caused by fire and the effect of the inclination of the gallery into consideration., The effect of the inclination of the gallery on the spread rate of the timber fire was quantitatively analysed for both upward and downward spread of fire. Buoyancy effects created by the fire in an inclined gallery contribute to reducing the pressure loss of ventilation in case of ascending ventilation and to increasing it in case of descending ventilation. A method is proposed for estimating the fire spread rate and the fire zone length, taking the variation of ventilation caused by fire and the effect of the inclination of the gallery into consideration.

The effects of ignition intensity, air velocity and fuel load density on the spread characteristics of mine fires were investigated., The effects of ignition intensity, air velocity and fuel load density on the spread characteristics of mine fires were investigated.

The air block system can be used at the leeward side of fires. The gallery can be rapidly sealed off with the curtain which is made of heat resistant material and is covered with a thin film of water., The air block system can be used at the leeward side of fires. The gallery can be rapidly sealed off with the curtain which is made of heat resistant material and is covered with a thin film of water.

The air velocity decreases as the fire burns. The higher the temperature of the fire zone and the initial air velocity, the greater is the decrease in the velocity. The air temperatures decreased nearly exponentially with distance from the fire., The air velocity decreases as the fire burns. The higher the temperature of the fire zone and the initial air velocity, the greater is the decrease in the velocity. The air temperatures decreased nearly exponentially with distance from the fire.

In a full scale extinguishing experiment against timber lining fire, it was possible to extinguish the fire perfectly by introduction of inert gas foam for 20 minutes and to maintain the inert atmosphere around the fire area due to the suppression effect of inert gas diffusion by films of foam. Thus, it is concluded that inert gas foam is much more effective than inert gas or foam alone to extinguish underground fires., In a full scale extinguishing experiment against timber lining fire, it was possible to extinguish the fire perfectly by introduction of inert gas foam for 20 minutes and to maintain the inert atmosphere around the fire area due to the suppression effect of inert gas diffusion by films of foam. Thus, it is concluded that inert gas foam is much more effective than inert gas or foam alone to extinguish underground fires.