The basic objectives of mine roadways are to provide sufficient cross sections to accommodate equipment, transport, personnel travel and ventilation. However, many roadways become damaged to the extent of needing maintenance, generally dinting, and in some cases requiring re-ripping. Strata conditions play important effects on stability of roadways and other mining activities. Weak rocks cause excessive roadway closures, and water softens some rocks and worsens the closure problem. Therefore, study on effect of mine water on the stability of underground coal mine roadways is important for underground coal mine development. A scientific discussion on the effect of water on the stability of roadways is given on the basis of results obtained by means of field investigation and laboratory tests. Based on analysis, rock in saturated condition has only between 0.19 to 0.49 of its compressive strength and 0.17 to 0.59 of its tensile strength in dry condition. Among the coal measures rock in research area, water has the most obvious effect on the strength reduction of shale. The slaking behavior of shale has also been the worst among the other. Field investigation of roadway driven in shale shown vertical closure in the wet and dry condition area reached 40–60 and 5–15 cm respectively, in 30 days after the drivage. Among the measures, drainage is considered to be the most economical and simplest method to reduce the water content in the rocks or the rock masses. 相似文献
In order to protect the safety of workers construction, as well as for environmental and cost reasons, efficient small-diameter
shallow tunneling methods have recently become increasingly important in regards to outside plant engineering such as for
water supplies, electricity, telecommunications and gas. The effects of the above projects in overcrowded urban areas are
significant and often result in substantial impact and traffic delays associated with a loss of travel time. Clearly the solution
to these utility placement problems, if the full impact of trench excavation is to be avoided, is trench less technology.
In particular, for construction work near existing facilities, underground tunnels that are excavated by slurry pipe-jacking
are being increasingly employed in order to avoid problems. Slurry pipe-jacking was firmly established as a special method
for the non-disruptive construction of the underground pipelines of sewage systems. Pipe-jacking, in its traditional form,
has occasionally been used for short railways, roads, rivers, and other projects. Basically the system involves the pushing
or thrusting of a drivage machine through concrete pipes ahead of jacks. This method utilizes mud slurry that is formed around
the pipes in order to stabilize the surrounding soil. Moreover, in recent years, the rectangular shape of the concrete pipe
in using slurry pipe-jacking was introduced due to the effective uses of the space. Based on his reason, the rectangular shape
of the concrete pipe is often adopted in Japan. From this point of view, this paper discusses the effect shapes have on the
stability of surrounding soil by means of the numerical analysis. Secondly, this paper discusses the performance of the mud
slurry around the drivage pipes by means of the two-dimensional Eulerian-Lagragian seepage analysis. Moreover, in slurry pipe-jacking,
the performance of the mud slurry plays an important role in the pushing process. Finally, the thrusts in slurry pipe-jacking
can be predicted accurately by evaluating the resistance between the mud slurry and the concrete pipes and the resistance
between the soil and the pipes in the curved jacking area.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
The hydraulic conductivity of an unconfined carbonate aquifer at the uplifted atoll of Minami-Daito, Japan, was evaluated by a combination of cross-spectral analysis, analytical solution, and density-dependent groundwater modeling based on observed groundwater levels in 15 wells and at sea level. The island area was divided into 10 subregions based on island morphology and on inland propagation of ocean tides. The hydraulic conductivity was obtained for each subregion using analytical solutions based on phase lags of M2 constituents of ocean tides at each well by assuming two aquifer thicknesses (300 and 1,800 m) and two effective porosities (0.1 and 0.3). The density-dependent groundwater model evaluated the hydraulic conductivity of the subregions by reproducing observed groundwater levels. The hydraulic conductivity in the subregions was estimated as 3.46?×?10?3 to 6.35?×?10?2 m/s for aquifer thickness of 300 m and effective porosity of 0.1, and as 1.73?×?10?3 to 3.17?×?10?2 m/s for aquifer thickness of 1,800 m and the effective porosity of 0.3. It was higher in southern and northern areas, and higher in interior lowland than in the western and eastern areas. Fissures and dolomite distributions on the island control differences of the omnidirectional ocean tidal propagation and cause these differences in hydraulic conductivity. The method used for this study may also be applicable to other small islands that have few or no data for hydraulic conductivity.
Faults are complex geological conditions that are commonly encountered during underground excavation. Many support schemes, such as using a single pilot heading method and 30-m-long borehole pre-grouting, have been implemented during the pilot excavation of an 800-m-deep underground opening that passes through large fault zones in East China. However, various geo-hazards, including groundwater inrush, debris flow, and roof collapse, are still occurring, which seriously threaten tunneling safety. To eliminate the geo-hazards and ensure tunneling safety, ground surface pre-grouting (GSPG) was proposed and implemented for the first time to reinforce the regional engineering rock mass for this proposed 800-m-deep underground opening passing through large fault zones. The minimum grouting pressure of GSPG at a depth of 800 m below the surface is put forward based on hydraulic fracturing theory, providing valuable guidance for GSPG engineering practice. Engineering practice demonstrates that GSPG eliminates geo-hazards, improves the objective rock mass stability, and ensures tunneling safety. Field measurements indicate that the displacement velocity of the surrounding rock shows an obvious fluctuation response under the influence of GSPG, and the impact of GSPG on the stability of the 800-m-deep underground opening that has been excavated dramatically decreases as the distance from the grouting borehole increases. Moreover, there is a strong negative exponential correlation between the maximum velocity of deformations and the distance from the grouting borehole. In addition, the safe distance underground during GSPG is greater than 137 m. 相似文献
The evolution of groundwater quality at a wet zone in Sri Lanka was made clear using field investigation, chemical and isotopic
analyses methods. In the wet zone, the concentrations of major ions and electrical conductivity (EC) in the groundwater are
low with small seasonal change. Except for sodium, silica and chloride, the EC and other major ion concentrations increase
along the groundwater flow direction. The contributions of bicarbonate and calcium ions to the increase in EC are the largest
among the major ions. The groundwater quality shows calcium-bicarbonate type, the initial stage of the Chebotarev series.
There is a seasonal change in isotopic composition. The isotopically lighter groundwater was found at the valley bottom in
the rainy season. Under the very heavy precipitation conditions, the slope of the regression line between δD and δ18O and deuterium excess for groundwater are close to 8 and 10, respectively. In other cases, the slopes of the regression lines
and deuterium excess are, less than 8 and 10, respectively.
Received: 5 August 1998 · Accepted: 19 October 1998 相似文献
Real-time generation and distribution of the New Generation Sea Surface Temperature for Open Ocean (NGSST-O) product began
in September 2003 as a demonstration operation of the Global Ocean Data Assimilation Experiment (GODAE) High-Resolution Sea
Surface Temperature Pilot Project. Satellite sea surface temperature (SST) observations from infrared radiometers (AVHRR,
MODIS) and a microwave radiometer (AMSR-E) are objectively merged to generate the NGSST-O product, which is a quality-controlled,
cloud-free, high-spatial-resolution (0.05° gridded), wide-coverage (13–63° N, 116–166° E), daily SST digital map. The NGSST-O
demonstration operation system has been developed in cooperation with the Japanese Space Agency (JAXA) and has produced six
years of continuous data without gaps. Comparison to in situ SSTs measured by drifting buoys indicates that the root mean-square error of NGSST-O has been kept at approximately 0.9°C. 相似文献
A 3.8-kin Coupled Ice-Ocean Model (C1OM) was implemented to successfully reproduce many observed phenomena in the Beaufort and Chukchi seas, including the Bering-inflow-originated coastal current that splits into three branches: Alaska Coastal Water (ACW) , Central Channel, and Herald Valley branches. Other modeled phenomena include the Beaufort Slope Current (BSC) , the Beaufort Gyre, the East Siberian Current ( ESC), mesoscale eddies, seasonal landfast ice, sea ice ridging, shear, and deformation. Many of these downscaling processes can only be captured by using a high-resolution CIOM, nested in a global climate model. The seasonal cycles for sea ice concentration, thickness, velocity, and other variables are well reproduced with Solid validation by satellite measurements. The seasonal cycles for upper ocean dynamics and thermodynamics are also well reproduced, which include the formation of the cold saline layer due to the injection of salt during sea ice formation, the BSC, and the subsurface upwelling in winter that brings up warm, even more saline Atlantic Water along the shelfbreak and shelf along the Beaufort coast. 相似文献
Iheya‐North‐Knoll is one of the small knolls covered with thick sediments in the Okinawa Trough back‐arc basin. At the east slope of Iheya‐North‐Knoll, nine hydrothermal vents with sulfide mounds are present. The Integrated Ocean Drilling Program (IODP) Expedition 331 studied Iheya‐North‐Knoll in September 2010. The expedition provided us with the opportunity to study clay minerals in deep sediments in Iheya‐North‐Knoll. To reveal characteristics of clay minerals in the deep sediments, samples from the drilling cores at three sites close to the most active hydrothermal vent were analyzed by X‐ray diffraction, scanning electron microscope and transmission electron microscope. The sediments are classified into Layer 0 (shallow), Layer 1 (deep), Layer 2 (deeper) and Layer 3 (deepest) on the basis of the assemblage of clay minerals. Layer 0 contains no clay minerals. Layer 1 contains smectite, kaolinite and illite/smectite mixed‐layer mineral. Layer 2 contains chlorite, corrensite and chlorite/smectite mixed‐layer mineral. Layer 3 is grouped into three sub‐layers, 3A, 3B and 3C; Sub‐layer 3A contains chlorite and illite/smectite mixed‐layer mineral, sub‐layer 3B contains chlorite/smectite and illite/smectite mixed‐layer minerals, and sub‐layer 3C contains chlorite and illite. Large amounts of di‐octahedral clay minerals such as smectite, kaolinite, illite and illite/smectite mixed‐layer mineral are found in Iheya‐North‐Knoll, which is rarely observed in hydrothermal fields in mid‐ocean ridges. Tri‐octahedral clay minerals such as chlorite, corrensite and chlorite/smectite mixed‐layer mineral in Iheya‐North‐Knoll have low Fe/(Fe + Mg) ratios compared with those in mid‐ocean ridges. In conclusion, the characteristics of clay minerals in Iheya‐North‐Knoll differ from those in mid‐ocean ridges; di‐octahedral clay minerals and Fe‐poor tri‐octahedral clay minerals occur in Iheya‐North‐Knoll but not in mid‐ocean ridges. 相似文献
We estimated the northward heat flux through the eastern channel of the Bering Strait during the ice-free seasons between
1999 and 2008. This is likely about half of the total heat flux through the strait. The net volume transport and heat flux
through the eastern channel of the strait were estimated from multiple linear regression models with in-situ/satellite remotely sensed datasets and NCEP reanalysis 10 m wind. The net volume transport was well explained by the west-east
slope of sea level anomaly and NNW wind component at the strait. On the heat flux, the contributions of both barotropic and
baroclinic components were taken into account. Estimated volume transport and vertical profile of temperature were used to
calculate northward heat flux through the eastern channel of the strait. The magnitude of the estimated heat flux is comparable
to estimates from in-situ measurements. Averaged heat flux in the eastern Bering Strait between 2004 and 2007 was about 1.9 times larger than that
between 2000 and 2003. Maximum heat flux occurred in 2004, and same magnitude of heat flux was estimated from 2005 to 2007.
This resulted not only from the increase in northward volume transport but also anomalous warm water intrusion from the Bering
Sea. Our results suggest a candidate among the important parameters controlling heat budget, which contributes to the Arctic
sea ice reduction, whereas more studies are required to confirm that this mechanism is actually responsible for the interannual
and longer timescale variability. 相似文献