scholarly journals Effect of Drainage and Consolidation on the Pore Water Pressures and Total Stresses within Backfilled Stopes and on Barricades

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
El Mustapha Jaouhar ◽  
Li Li
Keyword(s):  
Hydraulic Conductivity ◽  
Numerical Simulations ◽  
Young’S Modulus ◽  
Pore Water ◽  
Hydraulic Properties ◽  
Underground Mine ◽  
Filling Rate ◽  
Short Term ◽  
Pore Water Pressures ◽  
Backfilled Stopes

The pore water pressures (PWPs) and total stresses during the placement of a slurried backfill in underground mine stopes are the key parameters for the design of barricades, built to retain the backfill in the stopes. They can be affected by the drainage and consolidation of the backfill. Over the years, several studies have been reported on the pressure and stresses in backfilled stopes by accounting for the drainage and consolidation. Most of them focused on the pressure and stresses in the stopes, few specifically on the barricades. The effect of the number of draining holes commonly installed through the barricade has never been studied. In this paper, the influence of hydraulic properties and filling rate of the backfill, stope size, barricade location, and number of draining holes is systematically investigated with numerical simulations. The results show that the stresses in the backfilled stope and on the barricade largely depend on the filling rate, hydraulic conductivity, and Young’s modulus of the backfill. The draining holes can significantly decrease the PWP, but only slightly the total stresses on the barricades in short term.

Effect of drainage and sequential filling on the behavior of backfill in mine stopes

2014 ◽  
Vol 51 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Nawfal El Mkadmi ◽  
Michel Aubertin ◽  
Li Li
Keyword(s):  
Pore Water ◽  
Numerical Study ◽  
Water Drainage ◽  
Filling Rate ◽  
Mining Operations ◽  
Overburden Pressure ◽  
Filling Sequence ◽  
Pore Water Pressures ◽  
Backfilled Stopes ◽  
Excess Pore

Underground backfilling offers significant economic and environmental advantages to mining operations. There is however a limited knowledge and understanding of how the backfill behaves within mine stopes, which creates some concern regarding the risk of accidents with potentially serious consequences. It is thus important to investigate further the response of backfill to ensure safe working conditions and optimize the filling sequence. This paper presents key results from a numerical study aimed at analyzing the hydrogeotechnical response of backfill in a narrow vertical stope. The simulations illustrate how stresses are influenced by stope geometry, water drainage, and filling rate. Three main cases are presented here to illustrate these effects; namely, (i) simulation of dry (or drained) backfill, (ii) a rapidly filled stope with progressive drainage and consolidation, and (iii) sequential backfill placement with different filling rates. The third case includes a simulation with evolving properties due to the binder added to the backfill. The results from the numerical analyses show that arching effects develop within narrow backfilled stopes because of the stiffness contrast between the rock and the fill material. This can produce a significant reduction of the stresses (horizontal and vertical) in comparison with the overburden pressure. The simulation results also show the development of excess pore-water pressures after the placement of the saturated backfill within the stope. Drainage tends to reduce these pressures and increase the frictional stresses along the rock walls. The sequentially filled stope simulations show that a rapid filling rate produces much higher total stresses and excess pore-water pressures, compared to slower rates. The simulation of the cemented backfill, with evolving properties, indicates that the progressive changes can have a significant effect on the total and effective stresses in the stope. A discussion follows on the implications of these results.

scholarly journals Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

1986 ◽  
Vol 32 (110) ◽  
pp. 20-30 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Pore Water ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Friction Angle ◽  
Water Channels ◽  
Water Drainage ◽  
Short Term ◽  
Overburden Pressure ◽  
Melt Water ◽  
Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tan ϕ, where ϕ is the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such as h(x) = 3x1/2 (m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well below h(x) = 3x1/2.

scholarly journals Hydraulic Conductivity and Pore Water Pressures in a Clayey Landslide: Experimental Data

Geosciences ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 102 ◽  
Author(s):  
Caterina Di Maio ◽  
Jacopo De Rosa ◽  
Roberto Vassallo ◽  
Roberto Coviello ◽  
Giuseppe Macchia
Keyword(s):  
Experimental Data ◽  
Hydraulic Conductivity ◽  
Pore Water ◽  
Slip Surface ◽  
Field Tests ◽  
Hydrological Conditions ◽  
Pore Water Pressures ◽  
Landslide Body ◽  
Clay Formation ◽  
Stable Formation

To analyze the response to hydrological conditions of an instable slope in a structurally complex clay formation, the hydraulic conductivity of the subsoil was estimated and pore water pressures were monitored. Two types of field tests were carried out: falling head tests in the Casagrande piezometers and localized seepage measurements in test boreholes. The experimental data show that in a narrow band around the slip surface, the hydraulic conductivity is higher—more than two orders of magnitude—than that of the landslide body and of the stable formation. Furthermore, the data of a long-term monitoring by Casagrande piezometers and vibrating wire cells show that the response of pore water pressures to the site hydrological conditions along the shear band is far faster than in the landslide body and in the stable formation. The slip band seems largely connected to the atmosphere, and the water pressures in the band are correlated with the deep displacement rates of all the inclinometers crossing the active slip surface.

scholarly journals Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

1986 ◽  
Vol 32 (110) ◽  
pp. 20-30 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Pore Water ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Friction Angle ◽  
Water Channels ◽  
Water Drainage ◽  
Short Term ◽  
Overburden Pressure ◽  
Melt Water ◽  
Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tanϕ, whereϕis the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such ash(x) = 3x1/2(m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well belowh(x) = 3x1/2.

scholarly journals Changes in shaft resistance and pore water pressures during heating of an energy foundation

2020 ◽  
Vol 205 ◽  
pp. 05022
Author(s):  
Michael B. Reiter ◽  
Lydia Kurtz ◽  
Mohammed M. Attala ◽  
Tugce Baser
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Water ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Thermally Induced ◽  
Shaft Resistance ◽  
Pore Water Pressures ◽  
Energy Foundations ◽  
Surrounding Soil

This study focuses on the evolution of shaft resistance during operation of a geothermal energy foundation installed in a saturated glacial till layer. Energy foundations are a sustainable alternative to traditional space heating and cooling approaches for buildings. Despite efficient operational performance, there are still valid concerns regarding the effects of heating on the structural performance of foundations. To investigate the effect of heating at the soil-pile interface, four drilled shafts are utilized as energy foundations on the Urbana-Champaign campus of the University of Illinois and instrumented. Although the energy foundations are not yet operational, a theoretical investigation is possible to understand the effects of heating on the evolution of thermally induced pore water pressures and the shaft resistance of an energy foundation. A thermo-poroelastic numerical model is validated against an analytical solution, then is used to analyze the thermo-mechanical response of the soil-structure system under different conditions. The results indicate that the evolution of pore water pressure is affected by the rate of heating and the hydraulic conductivity of the surrounding soil, as expected. Higher pore water pressures are generated in the case of low hydraulic conductivity and higher rates of heating. Prior to the dissipation of excess pore pressures, the changes in shaft resistance are variable and influenced by the thermally-induced deformation of the foundation and the surrounding soil.

scholarly journals In situ equilibrium pore-water pressures derived from partial piezoprobe dissipation tests in marine sediments

2013 ◽  
Vol 50 (12) ◽  
pp. 1294-1305 ◽  
Author(s):  
Nabil Sultan ◽  
Sara Lafuerza
Keyword(s):  
Slope Stability ◽  
Pore Pressure ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Design Parameters ◽  
Short Term ◽  
Pore Water Pressures ◽  
Time Required

Excess pore-water pressure has a significant effect on submarine slope stability and sediment deformation, and therefore its in situ equilibrium measurement is crucial in carrying out accurate slope stability assessments and accurately deriving geotechnical design parameters. In situ equilibrium pore-water pressure is usually obtained from pore pressure decay during piezocone tests. However, submarine shelves and slopes are often characterized by the existence of low-permeability (fine-grained) sediments involving long dissipation tests that are an important issue for offshore operational costs. Consequently, short-term and (or) partial dissipation tests are usually performed and in situ equilibrium pore-water pressures are predicted from partial measurements. Using a modified cavity expansion approach, this paper aims to predict for four different sites the in situ equilibrium pore-water pressures. Comparisons between predicted and observed in situ equilibrium pore-water pressures allowed the development of a guide to evaluate the minimum time required to perform short-term dissipation tests for a given marine sediment. The main finding of this Note is that the second derivative of the pore pressure, u, versus the logarithm of time, t, ∂2u/∂ln(t)2 must be positive to calculate accurately the in situ equilibrium pore-water pressures from partial measurements.

scholarly journals Cylindrical Piezometer Responses in a Humified Fen Peat

1994 ◽  
Vol 25 (3) ◽  
pp. 167-182 ◽  
Author(s):  
Andrew J. Baird ◽  
Simon W. Gaffney
Keyword(s):  
Hydraulic Conductivity ◽  
Response Time ◽  
Pore Water ◽  
Test Data ◽  
Test Results ◽  
Recovery Test ◽  
Pore Water Pressures ◽  
Compressible Soil ◽  
Time Theory

Most studies of peat hydrology have concentrated on processes below the watertable where pore water pressures and hydraulic conductivity are measured using piezometers. While piezometer head recovery tests in poorly humified bog peats give responses similar to those expected from rigid soils, a number of studies have suggested that matrix compressibility might be important in affecting head recovery test results in well humified bog peats. Until now no data have been available for humified fen peats. We apply the response time theory of Brand and Premchitt (1982) for compressible soils, and Hvorslev (1951) for rigid soils, to head recovery test data obtained from open cylindrical piezometers installed in a humified fen peat in Somerset, England. To the best of our knowledge this is also the first quantitative application of compressible soil theory for piezometers to any peat. Our results show that compression and swelling of the peat matrix do affect the course of head recovery in the piezometers used in the study. We comment on the significance of this finding for the calculation of hydraulic conductivities and pore water pressures in this peat type.

Spatial Variation of Aquifer Parameters from Coastal Aquifers of Sindhudurg District, Maharashtra Using Pore-water Resistivity and Bulk Resistivity

2018 ◽  
Vol 1 (1) ◽  
pp. 28-40
Author(s):  
Suneetha Naidu ◽  
Gautam Gupta
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Water ◽  
Coastal Aquifers ◽  
Hydraulic Parameters ◽  
Formation Factor ◽  
Bulk Resistivity ◽  
Good Correspondence ◽  
Aquifer System ◽  
Transverse Resistance ◽  
Water Resistivity

Estimation of hydraulic parameters in coastal aquifers is an important task in groundwater resource assessment and development. An attempt is made to estimate these parameters using geoelectrical data in combination with pore-water resistivity of existing wells. In the present study, 29 resistivity soundings were analysed along with 29 water samples, collected from the respective dug wells and boreholes, in order to compute hydraulic parameters like formation factor, porosity, hydraulic conductivity and transmissivity from coastal region of north Sindhudurg district, Maharashtra, India. The result shows some parts of the study area reveal relatively high value of hydraulic conductivity, porosity and transmissivity. Further, a negative correlation is seen between hydraulic conductivity and bulk resistivity. The hydraulic conductivity is found to vary between 0.014 and 293 m/day, and the transmissivity varied between 0.14 and 11,722 m2/day. The transmissivity values observed here are in good correspondence with those obtained from pumping test data of Central Ground Water Board. These zones also have high aquifer thickness and therefore characterize high potential within the water-bearing formation. A linear, positive relationship between transverse resistance and transmissivity is observed, suggesting increase in transverse resistance values indicate high transmissivity of aquifers. These relations will be extremely vital in characterization of aquifer system, especially from crystalline hard rock area.

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