摘要:

Pumping (extraction, purge) wells in the waste may be proposed as part of the design of new landfills to backup the leachate underdrain system. These wells are intended to control the leachate mound after there has been a failure of the underdrain system. Pumping wells in the waste have also been proposed to reduce the height in old landfills that are not engineered with a leachate underdrain system. Equations are developed herein for use in estimating the well radius/spacing required to control the leachate mound to a specified level for a number of different assumed conditions and hence can be used to aid the design engineer in assessing the viability of pumping wells in the waste as a leachate control measure. The equations consider the hydraulic conductivity of the waste and the percolation through the cover. It is shown that leakage through the landfill base can be readily considered provided that the leakage through the base is less than 80% of the percolation into the landfill. Anisotropy of the waste is considered. Correction factors are also presented to account for the effect of a reduction in hydraulic conductivity around the well due to biotic and abiotic clogging. The use of the equations is illustrated by examples.Key words:pumping wells, landfills, leachate control, design, applications, clogging.

ISSN:0008-3674    

DOI:10.1139/t96-020

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Compacted bentonites are attracting greater attention as back-filling (buffer) materials for high-level nuclear waste repositories. For this purpose, it is very important to quantitatively evaluate the swelling characteristics of compacted bentonite. New equations for evaluating the relationship between the swelling deformation of compacted bentonite and the distance between two montmorillonite layers are derived. New equations for evaluating the ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of compacted bentonite, are proposed. Furthermore, a prediction method for the swelling characteristics of compacted bentonite is presented by combining the new equations with the well-known theorectical equations of repulsive and attractive forces between two montmorillonite layers. The applicability of this method was investigated by comparing the predicted results with laboratory test results on the swelling deformation and swelling pressure of compacted bentonites.Key words:bentonite, diffuse double-layer theory, van der Waals force, nuclear wastes disposal, swelling deformation, swelling pressure.

ISSN:0008-3674    

DOI:10.1139/t96-021

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Results of 43 load tests on driven and jacked piles performed at eight calyey sites have been back-analysed using piezocone test data. A method to evaluate the axial capacity of piles has been proposed in which the pile unit skin friction and the unit end bearing resistance are computed from the net corrected cone resistance,qnet. Correlation factors between piezocone and pile load tests were back-calculated using this approach. As most of the pile tests performed were tension tests, special emphasis was given to the evaluation of the pile unit skin friction.Key words:clay, pile, piezocone, cone penetration test, axial pile capacity, skin friction.

ISSN:0008-3674    

DOI:10.1139/t96-022

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Existing elasto-plastic critical state constitutive models for unsaturated soil provide no information on the variation of water content or degree of saturation. These models cannot therefore, for example, be used to predict unsaturated soil behaviour during undrained loading, when the variation of suction is determined by the requirement that water content remains constant. This problem has been tackled by extending an existing elasto-plastic model to include relationships describing the variation of specific water volume (the volume of water and solids in an element of soil containing unit volume of solids). The proposed form of the variation of specific water volume was based on consideration of the soil fabric, resulting in a coupled form of elasto-plastic behaviour. Predictions from the elasto-plastic model showed good agreement with the experimental results from suction-controlled triaxial tests on unsaturated samples of compacted speswhite kaolin. Normal compression lines for specific water volume at different values of suction were well predicted, as was the variation of specific water volume during wetting. Critical state values of specific water volume were slightly underestimated, but test paths for both drained and undrained shearing were predicted with reasonable success.Key words:compacted clays, constitutive model, critical state, elasto-plasticity, triaxial tests, unsaturated.

ISSN:0008-3674    

DOI:10.1139/t96-023

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The stability of spoil piles in surface coal mines is an important factor in the successful exploitation of coal reserves. Spoil pile instability must be avoided not only to ensure negligible risk in both personnel and equipement but also to prevent increased production costs. Since mining began at the Eskihisar strip coal mine, southwest Turkey, stability problems have been experienced in both spoil piles adjacent to highwalls (slices) and outside dumping areas. This paper outlines the results of field and laboratory investigations performed to describe the causes and mechanism of pile instabilities threatening production along the highwalls. Back-analysis of failures and monitoring data have revealed that failures occur along planar surfaces that define two-wedge shaped blocks. In addition, shear strength of the moist underclay at the base of piles and changes in the floor dip are the controlling factors in the development of failures. It is also noted that sharp decreases in shear strength after peak values for the the underclay indicated that weak basal planes exhibit a shear strength at or approaching the residual value at the time of failure. Results show that failures are most likely initiated along the spoil &#150 natural ground interface and propagate into spoil mass. Three possible remedial measures have been evaluated by carrying out two-dimentional stability analyses, and the most effective method for improving spoil pile stability appeared to be spreading of a rockfill material on the floor after coal production.Key words:back-analysis, biplanar wedge failure, pile instability, rockfill blanket, shear strength.

ISSN:0008-3674    

DOI:10.1139/t96-024

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Pile reponse to earthquake loading and soil–pile interaction behaviour were investigated experimentally using the hydraulic gradient similitude technique. The unique feature of this method is the application of a very high hydraulic gradient to increase the effective stresses in the model, simulating full-scale stress conditions in the field. The dynamic loading was applied to model piles using a conventional shake table. Tests on model piles embedded in dense sands are described herein. Both free vibration and forced vibration simulating earthquake loading were carried out. Pile bending moment, deflection, and acceleration were measured during testing. Dynamicp–ycurves were derived from the measurements and were found to be highly nonlinear and hysteretic at shallow depths under strong shaking. Thep–ycurves for low-level shaking showed essentially linear elastic behaviour. The experimentalp–ycurves were compared with the backbonep–ycurves for sand recommended by the American Petroleum Institute, and the agreement was reasonable except at shallow depths.Key words:pile, hydraulic gradient, modelling, vibration, shaking,p–y

ISSN:0008-3674    

DOI:10.1139/t96-025

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The use of prefabricated vertical drains (PVDs) for enhanced soil flushing was investigated using a bench scale experimental setup. Soil samples were prepared and saturated in contaminant recovery cells (CRC). The PVDs were installed in rectangular and circular configurations, and a vacuum was applied to recover subsurface water. A predictive model for contaminant transport using the PVD-enhanced soil flushing was developed and presented. Results from the CRC tests using four PVDs in a rectangular arrangement indicated that the volume of the retrieved fluid increased as a function of the vacuum level and was approximately 0.55 mL/s at a vacuum level of 9.0 kPa. This represented a recovery efficiency of approximately 100%, since the base inflow through the sample was 0.55 mL/s. Using six PVDs in a circular configuration with a spacing of 14 mm from the center of the circle, a flow rate of approximately 6 mL/s was recovered under 6.8 kPa of vacuum. The average drawdown under a vacuum of 8.6 kPa ranged from 15 to 45 mm, and the zone of effective drawdown was measured to be approximately 200 mm in diameter. This value is approximately 10 times the effective diameter of the PVDs. An injection–extraction test indicated that, under an applied injection pressure of 3.5 kPa, an injection flow rate of approximately 6.5 mL/s was measured. At a vacuum pressure of 6 kPa and using the cicular configuration, the injection and recovery flow rates were approximately balanced. Such balance is essential to avoid decreasing the flushing rate due to the compression of the soil voids as well as to avoid the desaturation of soil profile.Key words:contaminant transport, injection, model, prefabricated vertical drains, retardation, soil flushing, vacuum

ISSN:0008-3674    

DOI:10.1139/t96-026

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The behaviour of an instrumented section of a full-scale geogrid reinforced embarkment constructed on a very soft deposit of peat overlying organic silt is examined. The results of field monitoring are reportd together with engineering properties of the soils obtained from laboratory tests. The behaviour was analyzed using the finite element method, and the calculated performance is shown to be in good agreement with that observed.Key words:geogrid, reinforcement, embankment, peat, organic silt.

ISSN:0008-3674    

DOI:10.1139/t96-027

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The 1963 landslide on Mount Cayley, British Columbia, began at the head of Dusty Creek, a small tributary of Turbid Creek, a major creek draining Mount Cayley, and terminated at the present confluence of Dusty and Turbid creeks. About 5 × 106m3of partially saturated, columnar-jointed dacite and weak pyroclastic rocks moved 2.4 km downstream. The depletion zone contained three separate blocks. The landslide deposits have distinct layers that can be traced back to similar bedrock units in the undisturbed material, which are three times thicker. The accumulation zone is divided by two gullys into three blocks, which preserve, much thinned, different but overlapping portions of the volcanic stratigraphy. The 1984 rock slide on Avalache Creek, 0.8 km away, involved tuff breccia, tuff lapilli, and tuff, all easily broken. Its main track ran over thick snow and ice on the bottom of the creek. Differences in water content and displaced material led to different flow modes: the 1963 fragments formed laminar flows, which supported comparatively undeformed central plugs; the turbulent 1984 flow's deposits have no distinct layers. The two modes, laminar flow and turbulent flow, also formed different types of landslide dams.Key words:landslide, debris flow, volcano, British Columbia, tuff, lava

ISSN:0008-3674    

DOI:10.1139/t96-028

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The Norman Wells oil pipeline has been operating successfully for 10 years, transporting crude oil from the Norman Wells field in the Northwest Territories to southern markets. The temparatures of the oil in the pipeline have been closely monitored at several locations, and a detailed record of the thermal performance of the pipeline and the response of the surrounding permafrost soils is available. Recently, a geothermal program has been developed to predict the temparature profiles along a buried pipeline in more detail than has hitherto been attempted. The recently developed simulator accounts for freezing and thawing around the pipeline, while accounting for the heat losses from the pipeline to the ground as the contents flow through the line. The Norman Wells oil pipeline has provided an opportunity to test and calibrate the new model. Comparaisons between observed temperatures along the line and predictions from the simulator have been made, and the agreement is generally extremely good. The downstream effects of recent changes to the operating temperatures at Norman Wells were accurately predicted, illustrating the potential applications of model. The simulator will allow the effects of future planned changes in operating conditions to be more accurately evaluated, as well as playing an important part in design engineering studies for future oil, water, and gas pipeline projects elsewhere.Key words:pipeline, geothermal, oil temperatures. permafrost, thaw, Norman Wells.

ISSN:0008-3674    

DOI:10.1139/t96-029

出版商:NRC Research Press    

年代:1996

数据来源: NRC