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The use of grout in conventional reinforced masonry construction increases the cost and time of construction but allows walls subject to out-of-plane loads an enhanced ability to span between lateral support levels. An experimental investigation including a total of 21 walls was conducted in an attempt to identify potential alternatives to conventionally grouted walls. The strength and serviceability of walls containing unbonded reinforcement anchored at its ends was evaluated. All walls were two and a half blocks wide and 14 courses tall and were constructed in running bond using standard 200 mm concrete blocks. Six replicate unreinforced and partially grouted, conventionally reinforced walls served as control specimens. Walls with unbonded reinforcement were determined to be inherently stable with maximum loads approaching those of partially grouted, conventionally reinforced walls. If used in practice, these walls would need to be limited to indoor exposures due to the wide crack widths that develop.

Spatial variability in the radius of a jet-grout column is commonly encountered in practice. Although various prediction models for the column radius are available, they have been generally used to predict a nominal radius. The radius variation within a column has been seldom considered. In this study, the intracolumn radius variation was simulated as a lognormal stochastic process. This was done based on the existing prediction models where the column radius can be correlated with the undrained shear strength of in situ soils. A slab consisting of overlapping jet-grout columns was considered. The slab serves as an earth-retaining stabilizing structure in a deep excavation. The effects of radius variation on the mass performance of the slab were examined with the finite-element method. In addition, the positioning errors in jet-grout columns were also investigated. Owing to the random nature of the radius variation, Monte-Carlo simulations were performed to estimate the statistical characteristics of the mass performance of the slab. A strength reduction factor was introduced and tabulated to account for the effects of geometric imperfections in the column radius and column position. With the strength reduction factor, practitioners could quantitatively evaluate the effects of these geometric imperfections in design considerations. Practical recommendations on the column length and column spacing were also proposed.

To evaluate the diameter of jet grout columns actually formed under the ground, several methods had been developed over the past years. Nevertheless, uncertainty still exists in different methods mostly due to the variations of ground and grouting conditions. This study proposes an acoustic monitoring system capable of directly recording the jet grouting sounds detected at different distances from the jet nozzle. To correlate the actual diameter of the jet grout column with the monitored sound prints, a field test was conducted in an interlayered sandy and gravelly soil and the jet grout column was excavated for dimension measurement. The recorded sounds show that the distribution of the threshold peak amplitudes at different distances can be represented by the curve of the normal distribution function. In addition, the standard deviation and mean of the normally distributed threshold peak amplitudes can be used as indicators to determine the effective diameter of the jet grout column for a specific jet grouting project. Although this acoustic monitoring method would be costly and time-consuming if used to examine all jet grout columns, it is suitable for frequent use in trial tests for finding reasonable grouting parameters when forming jet grout columns with design diameters.

An innovative compaction-grouted soil nail was designed by injecting grout into a special latex balloon (grouting bag) to avoid bleeding and penetration of grout into the surrounding soil. A series of large-scale model tests was performed to study the surrounding soil responses due to grouting and the subsequent pull-out resistance of the soil nail. The experimental results show that grouting pressure plays an important role in the enhancement of the density and (or) strength of the surrounding soil. In addition, during the pull-out process, the compaction-grouted soil nail exhibits a strain-hardening behaviour without a yield point. This is a significant advantage of this new soil nail, indicating that it can enable soil masses to remain stable against a relatively large deformation before ultimate failure. The main factors behind the improvement of the pull-out resistance of the new soil nail are, first, the compaction–densification of the soil near the grouting bag due to grouting, resulting in the enhancement of the shear strength of the soil, and, second, the enlargement of the grouting bag, causing the increase of the interface shear and end resistance to the pull-out of the soil nail.

Permeation grouting using bentonite grouts is one of the effective methods to improve the engineering properties of granular soils. However, the low penetrability of bentonite grouts into soils limits their practical application in permeation grouting. This study presents a new approach to control the penetration length of bentonite grouts through granular soils using an ionic additive, sodium pyrophosphate (SPP). It is hypothesized that the chemical modification changes both rheological and physicochemical properties of the bentonite grout, and thus affects its penetration length through soils. The rheological properties (yield stress and apparent viscosity) of bentonite grouts with weight ratios (ratio of water to dry bentonite, W/B) of 19, 12.3, 9, and 7.3 were controlled by the addition of 1%–4% SPP by weight of dry bentonite. The bentonite grouts were also injected into sand columns prepared at various experimental conditions to evaluate the effect of each experimental parameter on their penetration lengths. The results show that the penetration length of bentonite grouts decreases with a decrease in W/B ratio and an increase in yield stress and apparent viscosity. Moreover, the penetration length increases with the increase of the normalized effective grain size and injection pressure, but the increase of fines content reduces the penetration length of the grouts. While the existing analytical equation produces good agreement with the measured penetration lengths for the grouts having high yield stress (>26 Pa), it significantly overestimates the penetration lengths of the SPP modified bentonite grouts due to filtration (especially, the grouts having low yield stress and low W/B ratios). Therefore, a new empirical correlation is proposed to predict the penetration length of the bentonite grouts based on filtration and rheological blocking.

An experimental program was undertaken to evaluate the performance of self-consolidating mortar designed for filling small annular spaces for the rehabilitation of underground water line or sewage pipelines. The study also intended to establish a testing protocol to validate the workability of repair grout. All the investigated mixtures had good filling and passing ability with adequate retention of workability over 3 h. The repair mortars exhibited high stability with bleeding lower than 0.3% compared to 3% bleeding in the case of the reference neat cement grout. The reference grout had a lower plastic viscosity and higher slump flow values than the sanded repair grouts. A V-funnel with 30 mm × 30 mm overture and a flow cone with 12.7 mm overture are recommended for mortar made with concrete sand with a 5 mm nominal size and micro mortar with fine sand with a nominal size up to 3 mm, respectively.

During construction of a double-o-tunnel (DOT), rolling will inevitably occur due to the following: (i) nonuniformity of subsoil condition, (ii) manufacturing errors in the DOT shield machine, (iii) different pulling forces at two sides of the DOT, (iv) effect of assembled segments, (v) loss of grout, and (vi) inappropriate operation. In engineering practice, rolling correction using a one-side load at the elevated side is a cost-effective method. The weight of the one-side load is determined by the experience of the engineers and (or) through observation of the returned rolling angle. However, these methods cannot predict the value of the one-side load before applying it. This paper presents a series of finite element analyses that was performed to investigate the relationship among the one-side load, rolling angle, and subsoil deformation. The analytical results show that the proposed approach can predict field-observed data well. It is concluded that analytical results can be used as guidance for DOT construction.

This paper summarizes the experimental results of a series of cyclic simple shear tests on liquefiable silty sand with and without sample improvement with colloidal silica grout. The objective of the paper is to evaluate the effectiveness of colloidal silica grouting in reducing the liquefaction potential of natural silty sand. Colloidal silica was selected as a stabilizing material due to its low viscosity, wide range of gel times, nontoxicity, and low cost. The soil tested in this experimental program is a poorly graded sand with 11.5% of nonplastic silt from the Port of Lázaro Cárdenas, México. Colloidal silica treated and untreated sand specimens show different pore pressure response and deformation behavior under cyclic loading in simple shear tests. The results indicate that, for a given initial relative density and initial effective vertical stress, liquefiable silty sand specimens stabilized with colloidal silica grout generally exhibit significant gain in liquefaction resistance compared with untreated specimens. It was also found that the colloidal silica grout reduces considerably the rates of pore pressure generation and shear strain of the silty sand specimens subjected to cyclic loading.

This paper presents an experimental investigation on the effect of the replacement rate and fineness of natural zeolite on the rheological properties of cement-based grouts. For this purpose, natural zeolites with two different finenesses were used to partially replace Portland cement at 20%, 30%, and 40% by weight. While preparing the grout mixtures, a constant water to cementitious material ratio (w/CM) of 0.60 was used together with a superplasticizer (SP). Setting times and compressive strength of grouts were also determined as part of the experimental study. Test results indicated that the rheological properties of cement-based grouts were significantly affected by the replacement rate and the fineness of natural zeolite. The replacement rate of cement by natural zeolite for a constant SP content significantly increased the yield stress and apparent and plastic viscosities, and reduced the fluidity and deformability of the cement-based grouts. Moreover, incorporation of a fine natural zeolite resulted in a further decrease in the rheological and workability properties of grouts. With an increase in the dosage of SP, both yield stress and plastic viscosity decreased significantly. Grouts made with natural zeolite also showed pseudoplastic behavior, and shear thinning increased with the increase of zeolite amount and fineness. Test results also indicated that the natural zeolite with different fineness had a marked effect on the setting time and compressive strength of grout mixtures. Therefore, the use of natural zeolite confirms that grouts with satisfactory rheological and mechanical properties can be successfully obtained.

Several bridge columns, in which concrete was delaminated as a result of steel corrosion, were repaired in the mid 1990s. Different types of grout, including one based on expansive cement, were used to rebuild the damaged columns to their original shape; the columns were then wrapped with glass-fibre-reinforced polymers (GFRPs). The associated lab study indicated that the observed damage caused a reduction of about 20% in the axial-load-carrying capacity of the columns and much larger reductions in ductility and energy-dissipating capacity. The experimental results also showed that the strength and ductility of the columns could be recovered by repairing them with GFRP. Long-term monitoring of three columns repaired in the field using GFRP has indicated their excellent performance. No deterioration has been observed in the fibre-reinforced polymer or in the columns in more than 10 years. Monitoring has also shown a reduction in the rate and associated risk of corrosion over time; thus, this is a more durable retrofitting technique than traditional ones, such as steel jacketing.Key words: concrete, columns, corrosion, cyclic loading, ductility, expansive cement, glass-fibre-reinforced polymers, monitoring, repair, strength.

Field trials were conducted to evaluate three different permeation grouts in a medium-dense, silty sand outwash deposit. Sodium silicate, microfine powder, and microfine cement based grouts were used. Visual observations from boreholes, a large-diameter shaft, and two inspection drifts through the grouted sand are reported. The sodium silicate grout produced a uniformly grouted material with massive structure. The microfine powder grout did not harden in the ground. The injection of the microfine cement grout resulted in only discrete veins of grouted soil. Laboratory testing of the grouted soil recovered from block samples quantified the strength increase of the sand grouted with sodium silicate. Cross-hole seismic velocity tests conducted through the grout zone prior to construction of the inspection shaft and drifts indicated increased velocities in the grouted soils. The successful trials established the suitability of the sodium silicate grout as a means of ground treatment for temporary support for tunnel excavation.Key words: permeation grouting, soil improvement, sodium silicate, microfine cement.

Grout-type transverse joints between precast concrete slabs were tested to study their static and fatigue behaviours. The tests were performed with loading equipment especially designed and constructed in the laboratory to introduce shear force on the joints of the test specimens. The aim of this study was to improve the shear and fatigue strength of grout-type transverse joints by identifying the effects of prestressing the specimens. The results indicated that longitudinal prestressing was an effective method to increase both the shear and fatigue strengths of grout-type transverse joints. Rational methods to estimate the cracking and ultimate loads for grout-type transverse joints are proposed based on the static loading tests. An estimation of the fatigue strength with respect to the amount of prestress is also suggested to aid in design of the grout-type transverse joint.Key words: grout-type transverse joints, precast concrete slabs, shear and fatigue strength, prestressing.

Three-dimensional finite element models of unreinforced hollow concrete masonry walls with one-course bond beams subjected to concentrated loading have been analyzed. The walls were modelled with different loading plate sizes, different loading locations along the wall (at the midpoint of the wall, at the end of the wall, and between these points), and different out-of-plane eccentricities (e = 0, t/6, and t/3). The hollow block units, mortar, grout, and bond beam blocks in the walls were modelled separately. Both smeared and discrete cracking methods have been utilized for predicting cracking under load. Geometric and material nonlinearities and damage due to progressive cracking were taken into account in the analyses. The predicted failure modes and ultimate capacities of the walls with the concentric concentrated load applied at the midpoint or at the end of the wall compared very well with the experimental results. When the load was between the midpoint and the end of the wall, the predicted ultimate capacity was between those for the load at the midpoint and at the end. The strength of the walls decreases with increasing out-of-plane eccentricities.Key words: finite element models, hollow masonry, smeared and discrete cracking models, concentrated load, loading locations, out-of-plane eccentricities.

An experimental programme was performed to study the behaviour of hollow concrete masonry wallettes with bond beams and vertical columns of grout subjected to concentrated loads. Forty-three wallettes were tested, with concentrated loads being applied either concentrically or eccentrically, through various-sized loading plates above the grout columns or on the bond beams above the hollow blocks. When the concentrated load was applied above the grout columns, the face shells of the hollow block units attached to the grout columns split and the columns subsequently crushed. When the load was applied on the bond beams, wallettes failed similarly to hollow masonry walls without vertical columns of grout, with web splitting and vertical cracking in line with the load, followed by face-shell spalling and (or) mortar crushing. When the eccentricity was one third of the wall thickness, failure was dominated by local spalling beneath the loading plate. The testing programme and mechanisms of failure are described, together with strength variation with increasing eccentricity, and dispersion of the concentrated load through the bond beam. General implications for the design of hollow concrete masonry with bond beams and vertical columns of grout subjected to concentrated loads are discussed.Key words: hollow concrete masonry, bond beam, grout columns, concentrated load, concentric, eccentric.

This paper presents the results of a thermomechanical simulation of freezing around an existing tunnel in Kobe (Japan) to predict the deformations associated with ice lens formation and those resulting from thaw after construction is completed. The frost heave characteristics used in the numerical model were obtained from laboratory freezing tests conducted on undisturbed samples provided by the Osaka Soil Test Laboratory. With the planned construction schedule, the predictions suggest a maximum frost heave at the ground surface of about 4.8 cm while the expected thaw settlement in the tunnel's centerline was about 13 cm. Observed frost penetration and surface frost heave movements agree well with the predictions. Grout injected during thaw was successful in preventing excessive thaw settlement.Key words: frost, soils, heave, model, monitoring, field.

As fractures in rock significantly reduce the strength as well as the stiffness of the rock mass, grouting may be required to improve the performance of the rock mass in engineering or mining projects. During grouting, mortar of cement or other materials is injected into the rock mass so that the fractures can be filled up and the rock mass can act as an integral unit. Unlike water, grouts are usually viscous and behave as non-Newtonian fluids. Therefore, the equations describing the flow of grout are more complicated and the solutions are quite difficult to obtain. The problem is further aggravated by the fact that the fractures are mostly randomly distributed, and it is rarely possible to accurately define the fractures and the distribution patterns. In this paper, a numerical model is proposed for analyzing the grouting process. The model is based on the stochastic approach, and it can provide the depth of penetration and the fluid pressure due to the flow of grout, which is modeled as a Bingham fluid, in the fractured rock mass. Parametric studies have been carried out to investigate the effects of various factors on the depth of penetration, and a regression formula is developed for calculating the penetration depth. Experiments have been carried out and their results are used to validate the present method.Key words: stochastic fractures, fractured rock mass, grout flow, grout penetration.

Rehabilitation of a watermain by grouted sliplining is usually carried out when the existing pipe is only partially deteriorated. Although designs that neglect the structural contributions from the existing pipe and the grout are generally conservative, the performance of the rehabilitated pipe needs to be better understood for effective design and management of buried water pipes. Presented in this paper is a practical method for the determination of load sharing and circumferential stresses in a sliplined pressure pipe. The laboratory tests show that the load carrying capacity of a cast iron pipe increases substantially after it is sliplined and grouted. Results also indicate that the eccentricity between the host pipe and the inserted pipe and the direction of eccentricity have an impact on the rupture load of the sliplined pipe. The effects of the host pipe wall thickness and the grout strength are also discussed. Although the method is based on a pressurized watermain, it can be used to assess the load carrying capacity of a non-pressurized pipe such as a sewer pipe. The use of this method is demonstrated through an example.Key words: performance, sliplining, watermain, circumferential stress, load sharing, grout, service life.

Several masonry structures, built over the past centuries, have to be restored to ensure their structural integrity and their conservation. Important research and development projects have been initiated by Public Works and Government Services Canada to rehabilitate some of these structures, such as the Rideau canal locks, by using a cement-based grouting technique. By following grouting pressures and flow rates, the stability of the structure is protected and the efficiency to fill openings is assured by using microfine cement-based grouts with admixtures. However, cement grout penetration cannot be observed with precision during the injection. The project described in this paper presents the grouting treatment of a Rideau canal lock sill wall that had to be demolished and reconstructed. The penetration of two different grout mixes was observed by removing the front row of blocks, piece by piece. A second phase of this study was conducted in the laboratory to compare the penetration of different grouts in a reconstructed granular material which simulated the lock's interior walls.Key words: restoration, masonry, grouting, groutability, cement grout, colloidal agent.

As part of the La Grande complex, in northern Québec, the development of the LG-1 hydroelectric project required the construction of a 2444 m long dyke on the north shore. The presence of a wide sensitive marine clay terrace covered with deltaic and river sand and silt deposits called for several design features, including the construction of a cement-bentonite cutoff through the sand and silt deposits on the terrace. This paper describes the different construction phases of the cement-bentonite cutoff with emphasis on excavation procedure and quality control.Key words: bentonite, cement, construction, cutoff, excavation, slurry trench.

Concentrated loads are one of the most common types of load applied to masonry walls. Concentrated loads occur under beams, trusses, and joists resting on a bearing wall ; they could also occur from the prestressing anchorages of a post-tensioned masonry wall. The current typical design detail of grouting some of the blocks in hollow concrete masonry beneath the concentrated load increases the bearing capacity of the wall. However, the present configuration of grouting is empirical, not being supported by any analytic procedure or published experimental data, despite the fact that it actually does improve the bearing capacity of the wall. An experimental investigation into the effect of grouting on the bearing capacity of hollow concrete masonry walls is described. A grout configuration is proposed, supported by a previous numerical analysis, which improves the bearing capacity of the wall beyond that obtained with the current pattern. The effect of the concentrated load location with respect to the block geometry on the wall capacity was also studied. The strength enhancement factors for the zone directly under the concentrated load are given for the walls analyzed. Recommendations for both the best location of the load with respect to the block geometry and grout configuration beneath the load are provided.

The paper discusses the application of a transient pressure pulse technique for the laboratory evaluation of the permeability characteristics of a cementitious grout material with a relatively low permeability. The experimentation involves the internal pressurization of a cylindrical grout specimen with a concentric circular cavity. The time-dependent decay of the fluid pressure within the cavity is used as the basis for the computation of the permeability of the grout. The paper presents details of the experimental methodologies and the mathematical procedures which are used to evaluate the permeability. The results of a series of radial flow pressure pulse tests are used to ascertain the permeability characteristics of a cementitious grout.

Many parameters affect the behaviour and failure of face-shell bedded hollow masonry subject to concentrated load. Detailed study of these parameters is needed to develop realistic design rules for this situation. The effects of loaded length and wall dimensions on capacity of the face-shell bedded hollow masonry subject to concentrated load are studied; the effect of mortar joint strength is also evaluated. The current design detail of filling some of the blocks under the concentrated load with grout is reviewed. The study was performed with a nonlinear elastoplastic finite element model that takes into account geometric and material nonlinearities as well as damage due to progressive cracking. The methodology, when combined with substructuring, allows analysis of substantially larger walls than would more typical three-dimensional analyses. The results indicate that the length of the loading plate is the significant parameter for load capacity. A possible design equation for plain hollow masonry subject to concentrated loads, concentric across the width of the wall, is provided. Adjustments could be made given the precise loading detail specified. Improvement details are explained. Key words: masonry, hollow concrete masonry, finite element modelling, cracking, failure, strength-enhancement factor, concentrated loads.

Direct penetration exploration tools such as the electric cone penetrometer (CPT) and piezocone (CPTU) are being increasingly used for site investigation studies to evaluate stratigraphy and obtain groundwater samples. Most of these techniques are considered full-displacement direct-push or direct-drive penetration methods which can leave open pathways that may allow the movement of surface or subsurface contaminants into uncontaminated layers. Sealing techniques are needed to protect groundwater conditions following the use of these types of exploration tools. A survey of industry techniques for sealing CPT holes indicates that a number of methods can be used to place grout mixtures and other seal materials into a hole either (1) after pulling the tool, (2) as the tool is pulled, or (3) simultaneously with advance of the tool. Selection of a particular method depends primarily on the soil and groundwater conditions at a given site but may also depend on other variables such as equipment availability, time, and cost. In some cases, the method of sealing may be dictated by a regulatory agency. Seal materials used for this practice typically consist of grout mixtures composed of bentonite slurries, neat cement, a combination of the two, or dry granular bentonite, which are placed to provide permanent low hydraulic conductivity barriers. A number of techniques that have been used to seal CPT holes are described, and the advantages and disadvantages of the various techniques are presented. Key words : groundwater, cone penetrometer, hydraulic barriers, contaminants.

A nonlinear three-dimensional finite element model was developed to study the complex behavior of ungrouted and grouted concrete block masonry prisms under axial compression. The model detects crack initiation and traces crack propagation in the masonry assemblage. Variable strengths for blocks, mortar, and grout were used to study the effect of the mechanical properties of prism constituents, and their combinations, on the prism strength and modulus of elasticity. The effect of the number of courses was also investigated. The results of the finite element analysis were used to develop simplified relationships to predict prism strength and modulus of elasticity. Good agreement was observed between the available experimental data and the predicted prism strengths. Key words: compressive strength, concrete blocks, failure modes, finite element, masonry, modulus of elasticity, prisms.

LG-1 hydroelectric project, part of La Grande Complex in northern Quebec, required the construction of a 2444 m long dyke on the north bank. The presence of sensitive marine clay, with deltaic and river sand and silt deposits on top of the clay in the central terrace, called for special design features. These included the construction of a dyke with side berms in a depression to ensure stability and the construction of a cement–bentonite cutoff through the sand and silt deposits of the terrace. This paper describes the different phases of dyke construction with emphasis on foundation treatment and construction techniques. Key words: bentonite, cement, clay, construction, cutoff, dyke, excavation, foundation, slurry, trench.

Because a modern diaphragm-type piezometer tip only requires a small change in fluid volume for pressure equalization, the conventional, large sand intake zone around the piezometer tip can be omitted, and the tip can be grouted in a borehole with cement–bentonite grout. This grouted-in installation method allows simpler and easier installation, accurate readings, fast response to changing formation pore-water pressures, installation in boreholes shared with other geotechnical instruments, and can save 10–75% on the installation cost of a piezometer. The grouted-in installation method can be used for most soil conditions provided that the grout is less permeable than the formation. A theoretical basis for the grouted-in installation method is presented with supporting laboratory and field data from the Syncrude Canada Ltd. oil sands mine. Key words : piezometer, grout, instrumentation, hydraulic conductivity, hydrodynamic time lag, oil sands.

The injection of grout in the microfissures of concrete dams in operation is very tricky because of the high pressures required to penetrate the slightly opened fissures. These conditions of grouting may result in the propagation of the fissures and contribute to the loss of stability of the mass. The technique using acoustical emission to follow the injection in real time has been evaluated. Water injection tests have been carried out on large dimensions (2.64 m × 1.42 m × 0.40 m) fissured concrete slabs instrumented with pressure, load, and displacement transducers. According to a study comparing two types of acoustical emission transducers, the low-frequency transducers would be more appropriate for this type of application. Moreover, the detected acoustical signals are not due to a constant pressure flow, but to the accelerations and decelerations of the grout, and to the mechanisms resulting from the variations of pressure and flow of the fluid (opening and closure of the fissure). Thus these observations confirm that the acoustical emission may be an interesting means to control the injections and, in particular, to determine the process of grout flow. Key words : concrete, fissure, injection, water test, pressure, acoustical emission. [Journal translation]

A grout for use in pile installation in permafrost is described. The high alumina cement (Ciment Fondu) based grout cures by rapidly evolving heat which maintains it above 0 °C until it hydrates and hardens. The laboratory development program of the mix design along with the cement admixtures which allows the grout to cure at temperatures as low as −10 °C and to remain workable during field use is reviewed. The development of installation procedures for the grout during construction of short range radar foundations is described along with field measurements of the compressive strength and the temperature profiles of the grout after placement in permafrost as cold as −14 °C. The Ciment Fondu grout performed according to the design requirement of hardening without freezing in permafrost colder than −10 °C during the installation of about 2000 piles for part of the short range radar project. Key words: permafrost, grout, laboratory, field, installation procedure, mix design.

The results obtained from 14 pile load tests carried out in saline permafrost at Iqaluit, Northwest Territories, are analyzed with respect to (i) the development of load along the length of the piles as determined from strain gauges mounted along the embedded portion of the piles; (ii) the time-dependent displacement of the piles under a constant load; and (iii) the performance of grout as a backfill material. The grout used as a backfill material cured adequately and provided sufficient bond strength between the anchor and the grout to cause either the anchor to yield or failure in the surrounding frozen soil. The development of load along the pile resulted in a nearly uniform stress distribution for smooth-surfaced piles but was highly nonuniform when lugs were added. Time-dependent displacement of the piles without lugs can be described using a power-law relationship. Key words : permafrost, saline, pile, load test, field, in situ capacity, load transfer.

At present time, in frozen rock, the anchors are not grouted with conventional cement grouts as these are inefficient, or deteriorate with the formation of ice lenses during the freezing of the mixing water. The problem is avoided by boring deeper into the rock mass, until the unfrozen horizon is reached, if accessible, or by using thermal protection systems, which result in additional costs. Substantial economies may be obtained by grouting the anchor in the frozen rock, along a length necessary and sufficient to insure the stability of the structure, by using an antifreeze grout with a Portland cement base without resorting to thermal protection. In this context, the results of a study carried out in the Far North are presented, including pull-out tests of anchors grouted with a Portland cement base grout in a rock frozen at −12 °C. The resistance to frost of the cement grout has been achieved by using an antifreeze chemical admixture, the sodium nitrate (NaN02), which has allowed the setting of the anchors without heating the steel bars, the rock, or the grout. The results obtained show that the cement grout used may be considered as an efficient grouting product for the design of grouted anchors in the frozen rock or in the permafrost of the Canadian Far North. Key words: frozen rock mass, permafrost, grouted anchor, pull-out test, Portland cement grout, antifreeze chemical admixture, Canadian Far North, Arctic.

The findings of a laboratory study on the time-dependent displacement of model piles in saline frozen soil are reported. The short-term time-dependent pile deformation in ice-poor saline silty sand was best described using a simple power law of time, whereas the long-term time-dependent deformations were best described using a flow law formulation similar to that used to describe the long-term time-dependent deformation of ice or ice-rich permafrost. The use of cementitious grout as a backfill resulted in doubling of the pile load carrying capacity for a given displacement rate. The laboratory test results compare well with other laboratory and field studies. Key words : frozen soil, saline, model pile, time-dependent deformation, sand backfill, grout.

The paper describes the design of and construction experiences at a 20 m deep vertical excavation that was required in the heavily built-up downtown Vancouver area. The subsurface conditions may be generalized as an upper 3 m of sand and gravel followed by a sandstone sequence from fine to coarse with increasing depth. Depending on grain size and cementation, the compressive strength of sandstone varied from 6 to 30 MPa.The excavation support system consisted of soldier piles and posttensioned anchors in the overburden and posttensioned anchors and shotcrete in the rock face. Drainage control was provided by a system of deep, vertical perimeter drains connected to a number of near-horizontal drains in the rock face.The paper describes design considerations for the excavation, including an estimate of seismic-induced deformations. The construction aspects described include the use of a rapid cure method to predict grout strength, the use of couplers in anchor bars, and anchor load tests. During construction, a number of failures, attributed to stress corrosion, occurred in high tensile strength steel anchors. The details of the investigation and testing program used to provide an estimate of remaining anchor life are described. Finally, the paper summarizes results from the field instrumentation. Key words: anchors, construction, corrosion, deformation, drainage, excavation, failure, grout, instrumentation, stress.

Conventional cements have proven to be unsuitable for subsurface concreting in permafrost and as a result cast-in-place piles have seldom been used in arctic regions. The petroleum industry has developed a gypsum-based cement that has been satisfactorily used to grout well casings through permafrost.Laboratory studies have been undertaken to evaluate the suitability of this cement for subsurface concreting in permafrost. It is concluded that this cement does have an adverse effect on the adfreeze bond strength and hence should not be used for cylindrical friction piles. However, it appears from this preliminary study that the cement does have potential for use as a construction material for cast-in-place belled and tapered piles.

The addition of cement to a bentonite slurry gives a complex material called self-hardening grout which slowly sets to become a clay-like solid. The properties of these mixes are highly dependent on the bentonite and the cement used. Most information available up to now comes from European countries where the technique has been developed. As very little information was available about such mixes in North America, an experimental program was initiated to study their applicability for cutoff walls of certain dams of the James Bay hydroelectric project. The present paper describes the characteristics of different mixes tested in their fluid and solid states. Keywords: bentonite, cement, slurry, cutoff wall.

In Thunder Bay, Ontario, a 2.16 m diameter tunnel is nearing completion in a soft to firm clay using a full-face tunnel boring machine and an unbolted precast segmented concrete lining. The lining consists of rings composed of four trapezoidal sections of unreinforced concrete, 1 m in length and 11 cm thick. Each ring is assembled within the protection of the tailpiece of the tunnel boring machine and clay grout is injected behind the ring as the machine advances by thrusting on the completed lining.Because of the uniqueness of this method of construction, an extensive field instrumentation program was undertaken to evaluate the tunnelling procedure and the performance of the completed tunnel. The first phase of instrumentation involved a 60 m length of the tunnel and included observations of ground surface deformation, soil deformation (as measured by slope indicators, magnetic extensometers, and deep settlement points), total pressure on the lining, and deformation of the lining. The information also included tunnelling procedure and weight of spoil removed as the tunnel boring machine passed through the instrumented area.These observations are presented and discussed. Some problems of instrumentation are considered, particularly as they related to the second array of instrumentation which was designed to provide detailed information on spatial deformations and pore pressure changes.

The dimensioning of anchor bars grouted in rock takes into account the mechanical properties of the three components steel, grout, and rock. The allowable bond strength at the rock–grout interface recommended by different national codes is generally selected according to the type of rocks and assuming an ordinary cement grout. In the present approach, the influence of the type of grout on the pull-out strength of anchor bars in a sound rock mass with mechanical properties equal or higher than the grout is considered. This experimental study shows that certain cement grouts can develop pull-out strength clearly higher than those obtained with epoxy grouts for example. Key words: rock mass, grouted anchors, cement grouts, epoxy grouts, pull-out test, creep test. [Journal translation]

During summer, it is possible to inject Portland cement grout in the Arctic because there is a layer of unfrozen rock surface which is approximately 2 m deep. During the month of August, the temperature of the unfrozen rock layer reaches +5 °C at a depth of 1 m, which allows the Portland cement to harden in good conditions and to acquire its full strength.After 7 days, the mean shear strength to failure at the rod–group contact, determined when the anchorages were pulled out, was 10 MPa. After 1 year, this strength was close to 20 MPa. These results are similar to those recorded in Sherbrooke for the same grout formulas. Key words: anchorage, cement grout, rock, Arctic, tearing off. [Journal translation]

The hydraulic efficiency of a double-wall cutoff built through 126 m (420 ft) of pervious alluvial deposit filling a V-shaped canyon and under a 107 m (350 ft) high earthfill dam is discussed. The cutoff walls are made up of cast-in-place concrete interlocking piles and panels and are intended primarily to minimize the danger of piping, by controlling the pore pressures in the downstream zone of the dam. The behaviour of the cutoff, monitored by a comprehensive instrumentation program, indicated after [Formula: see text] years a relatively high hydraulic efficiency (over 92%). During this period the cutoff has exhibited a very slight decrease in its efficiency (less than 1%), probably due to leaching of the grout at the rock-wall contact in the grout curtain, and probably also due to some removal of the bentonite from between the piles and panels. The analysis of the efficiency of each wall considered individually (using Casagrande's latest recommendation) indicates a lower efficiency for the upstream wall as compared to that of the downstream wall, probably because of the migration of bentonite particles downstream under the hydraulic gradient. The double-wall cutoff exhibits an efficiency about 18–30% higher than that for a similar single-wall cutoff.

Geotechnical investigations revealed the presence of high hydraulic conductivity zones with high grout takes in the left abutment of King Talal Dam. Control measures were needed to protect the foundations against the anticipated high leakage losses as well as against the probability of piping erosion, which may develop along the weakness and high hydraulic conductivity zones. The porosity, hydraulic conductivity, and groutability characteristics of the geological formations of the left abutment were investigated in detail. The data were analyzed and conclusions were made concerning the heterogeneity of the geotechnical properties of the different geological formations, the effectiveness of cement–bentonite grouting in improving the hydraulic conductivity and groutability characteristics of the foundation materials, and the measures taken to safeguard the foundations of the dam against the potential dangers of piping erosion.

Grouts in post-tensioning ducts can cause cracking of the structural member if the grout freezes at an early age. This laboratory program examines a range of cement–water grouts with differing w/c ratios, air contents, and ages. A new empirical test method employing a test bottle was introduced to study the performance of grouts during early freezing.It was determined using the bottle method and other experimental and analytical procedures that excessive grout dilation during early freezing could be avoided if the entrained air content of the grout exceeded[Formula: see text]where w/c is the original water-to-cement ratio of the grout and M is the fraction of the cement that has hydrated before the grout freezes.

A granite core containing a natural fracture, oriented parallel to the core axis, was collected, prepared, and its permeability measured in a hydrostatic test cell at different confining pressures. After the permeability hysteresis had been removed by several cycles of increasing and decreasing confining pressure, grout was placed within the fracture plane and allowed to cure for 40 days. Distilled water was forced through the sample until a significant flow rate developed. The influent solution for the sample was changed twice during the study to examine the effects of differing concentrations of Ca(HCO3)2 solutions on calcite precipitation within the fracture plane. The interaction of the Ca(HCO3)2 solution with the grout material resulted in a decrease in the permeability of the fracture plane over several months. At the close of the experiments, the sample was removed from the hydrostatic cell and opened along the fracture plane. The fracture exhibited two discrete braided channelways each with an average width of 2 mm. Precipitated calcite formed a rind along the walls of the channelways averaging 0.25 mm in thickness. The quantity of calcite precipitate determined from physical measurements was in reasonable agreement with that calculated using reaction rate expressions for calcite precipitation. The results of this study suggest the possibility that strategically located geochemical material could induce a geochemical evolution of groundwater within poorly grouted fractures, so as to decrease the permeability of the fractured rock system. Keywords: fracture permeability, grouted fractures, geochemistry, laboratory experiments, calcite precipitation.