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In order to improve the understanding on static liquefaction phenomenon, this paper presents an insight into the instability mechanism of a silty sand originating from the Sakarya region (Turkey). Monotonic undrained simple shear tests were performed in either strain-controlled or stress-controlled modes. The interpretation of the experimental results allowed us to draw three interesting conclusions on instability conditions: (1) Hill's stability postulate can be conveniently used to identify the onset of instability for strain-controlled tests, whereas in stress-controlled conditions, an alternative new parameter η* (modified apparent viscosity) was introduced. Depending on the strain rate, η* allows to identify stability conditions more clearly than second-order work; (2) the value of the pore pressure ratio at the onset of instability (ru,is), ranging between 0.30 and 0.50, is linearly linked to the state parameter ψ ; and (3) at the onset of instability, the dependence of both the major and minor principal stress directions (αis and βis) and Lode's angle (θis) on ψ was also observed. These findings are expected to be of some help for a more consistent approach to the constitutive modeling of the static instability mechanism. [ABSTRACT FROM AUTHOR]

Colloidal silica (CS) grouting is a soil improvement technique for seismic liquefaction risk mitigation consisting of the injection of a time-hardening, colloidal silica–based grout into potentially liquefiable sandy soils. A published laboratory test database—consisting of cyclic undrained triaxial tests on liquefiable clean untreated sand and on sand stabilized by 5% CS under different levels of initial stress anisotropy—is here discussed following an energy-based approach. The test results are presented and analyzed in terms of dissipated energy during cyclic loading. The obtained results show that (1) the development of dissipated energy is clearly related to the buildup of residual extra pore water pressure only for untreated sand samples; (2) under the same testing conditions, the dissipated energy at failure is significantly higher in stabilized sand than in untreated sand; and (3) the dissipated energy at failure is found to be independent of the cyclic stress amplitude and dependent on the degree of initial stress anisotropy for the untreated sand, while opposite trends are observed for stabilized sand. Therefore, contrary to the untreated sand, there is no evident advantage for using the dissipated energy at failure to assess the capacity of the stabilized sand. [ABSTRACT FROM AUTHOR]

Backfilling is critical to deep and high-stress mining in order to minimize stress redistributions in the host rock, which can lead to mining-induced seismicity and underground excavation collapse. Cemented paste backfill (CPB) is the most popular backfilling material in the mining industry; it is a mixture of mine tailings, binder, and water, which tightly fills the mined-out space, providing optimum regional ground control. This paper presents the results of a laboratory study of the evolution of the coefficient of at-rest earth pressure (K0) of a typical CPB material. The impact of parameters such as cement content and curing time on K0 and one-dimensional behavior of a CPB in stresses up to 1.8 MPa was studied. In general, K0 behavior is characterized by three regions: elastic, transitional, and posttransitional. Fitting functions are proposed to predict evolving K0 based on cement content, specimen curing time, and unconfined compressive strength (UCS) as the most common laboratory test in geomechanical engineering practices. Although the calibrated functions are specific to the material tested, the testing approach can be used to characterize other mines' backfills. [ABSTRACT FROM AUTHOR]

Concrete encasements are usually utilized to protect bridge above-ground piles from corrosion. These concrete encasements are usually square or round shapes reinforced by longitudinal rebars. However, the contributions of concrete encasements are not considered in traditional pile design procedures. On the other hand, rating engineers need to have realistic evaluations of the piles to estimate the capacity of the foundation for scour-critical bridges. Underestimation and overestimation of pile capacity can result in either potential bridge failure or uneconomical assessment. The objective of this paper is to investigate the effect of concrete encasement on pile buckling behavior subject to concentric load. To achieve this objective, four full-scale concrete encased pile specimens with various pile and concrete encasement lengths were fabricated and tested with concentric axial loading to measure the specimen ultimate capacity. In addition, the finite-element (FE) approach was utilized to simulate the buckling behavior and predict the ultimate capacities of the lab-tested specimens. The developed FE models were validated against the laboratory test data. Finally, the validated FE models were utilized in the parametric study to investigate the effect of the length and shape of the concrete encasement on the ultimate capacities of the steel H-piles. The results indicated that the concrete encasement could increase the buckling load of the pile, and ignoring the effect of the concrete encasement, as with the use of the equations suggested by the AISC, could result in a significantly underestimated prediction. It was also found that the concrete encasement increases the initial axial stiffness of the pile before the buckling load is achieved. [ABSTRACT FROM AUTHOR]

The vacuum preloading combined flocculation and solidification method (VP-FSCM) has been proposed in recent years to increase the efficiency of high-water-content slurries. The characteristic of the strength development of cement-treated mud, especially in the early stage, has significant effects on the consolidation process in the application of the VP-FSCM. An appropriate model for strength development can help decide the design scheme for the combining method to ensure that a high stabilization efficiency of high-water-content slurries is achieved. In this work, laboratory tests are conducted to investigate the strength development of mud with low cement dosage from a very early stage using vane shear tests and unconfined compression tests. After integrating the strengths obtained from the two approaches, the strength development behavior is analyzed, and the offset time is valued by performing a back-analysis using a modified Gallavresi's equation. It is found that a linear model can be built between the offset time and the water–cement ratio for a series of samples with the same soil type and binder type. Based on the model, the actual and predicted strength values fit well with a correlation coefficient of above 0.998. The model also agrees well with the test data from other literature, thereby testifying to its accuracy. By implementing the proposed model using consolidation theory, the consolidation proceeding time in the combined improvement method is determined. [ABSTRACT FROM AUTHOR]

This study presents a new design of a wood–concrete connector that meets ductility and stiffness requirements in accordance with Eurocode 4. An analytical approach and a numerical model developed on Abaqus are proposed. The study is completed by experimental push-out tests and a specially made composite beam. Two types of timber concrete composite (TCC) are considered in this study. The first connector (stud connector), was applied in construction and its performance compared to that of a recently developed connector. The analytical calculation of stiffness was performed using the relevant standard. In addition, different connector configurations and spacing were tested in push-out and beam tests. The results showed that this new connector has interesting characteristics such as stiffness (4,068.12 kNm2) and maximum strength (24,70 kN) compared to existing connectors. [ABSTRACT FROM AUTHOR]

This paper presents the results of 10 laboratory tests performed on closely spaced built-up members fabricated from hot-rolled angle sections. Such members are of special interest in the construction and reinforcement of steel lattice towers used for telecommunication or electrical transmission lines. The angle sections used in this study were star-battened with pinned support conditions. In particular, two configurations were studied: star-battened angles with equal sections (SBE) (composed of two chords with the same section), and star-battened angles with unequal sections (SBU) (composed of two chords with different sections). The influence of connection spacing along the members and different types of connections (fully preloaded bolts, partially preloaded bolts) were also studied. In addition, the important influence of geometric imperfections on failure load and failure mode were analyzed. In this paper, a numerical model is introduced after the laboratory tests are presented. The model was built in ANSYS version 18.2 and was validated based on the results obtained during the experimental campaign. The numerical results highlighted the sensitivity of failure modes to initial imperfections (out-of-straightness, load eccentricity). Last, the validated numerical model is thought to be used in a wider parametric study with the aim of developing new design recommendations. [ABSTRACT FROM AUTHOR]

Laponite is a nanomaterial that can modify the behavior of the fluid in which it is dispersed, transforming it into a non-Newtonian fluid with initial low viscosity that hardens with time. Additionally, since the gel recovers after shear stress has been removed, it has resilient properties. In this study, several series of laboratory element testing, such as oedometer, drained, and undrained tests, were performed to assess the effect of adding 1% laponite on the geotechnical properties of loose saturated sand. The results of one-dimensional consolidation tests indicated that the addition of laponite did not influence the compressibility of the host sand, but monotonic undrained tests showed that laponite could reduce friction between particles. Furthermore, the laponite's ability to recover was evaluated by subjecting the treated samples to a series of three cyclic loading phases. These specimens require up to 100 times more cycles to liquefy compared to untreated sand specimens with a similar relative density. [ABSTRACT FROM AUTHOR]

Induced partial saturation (IPS) is considered to be one of the most promising technologies to tackle soil liquefaction risk. The mitigation of the liquefaction susceptibility of loose partially saturated sandy soils is linked to the high volumetric compressibility of the gas or air bubbles entrapped in the continuous water phase. Based on a large amount of experimental data, a new formulation of the potential volumetric strain (εv*) of nonsaturated soil is introduced to overcome some experimental inconsistencies linked to the possible dissolution of the air bubbles, that may not be neglected at the laboratory scale if cyclic loads are applied with low frequencies (<1 Hz). Gas dissolution increases the volumetric strains, and if neglected may lead to unconservative estimates of the beneficial effect of desaturation on liquefaction potential. The experimental results of this study also showed that the difference in liquefaction resistance between partially saturated and fully saturated soils depends only on the volumetric component (Ev,liq) of the specific energy spent to attain liquefaction. Such a synthetic state parameter satisfactorily allows predicting the liquefaction resistance curves of partially saturated sands. [ABSTRACT FROM AUTHOR]

In this study, the suction induced by stress release was investigated by measuring the suction of instantaneously unloaded MX80 bentonite specimens after wetting in an oedometer either under different vertical stresses or under a constant-volume condition. Swell-consolidation tests were also performed, and the results were compared with those of specimens wetted under different vertical stresses or a constant-volume condition. The microstructure of the unloaded specimens was investigated using mercury intrusion porosimetry (MIP). The water content and void ratio as well as the degree of saturation of specimens were also determined. Results showed that in the case of limited water exchange between macropores and micropores during stress release, the change in suction was equal to that of stress (−ds/dσv=1). By contrast, with water exchange between macropores and micropores, soil swelling occurred, and the variation of suction was higher than that of stress (−ds/dσv>1). A method was proposed allowing such water exchange between macropores and micropores to be determined (−ds/dσv−modified=1 , where σv−modified is the modified stress considering water exchange), evidencing the macropore drying due to stress release. Comparison of results from MX80 bentonite and other clayey soils showed that when the nonclay (grains such as quartz, calcite, and so on) fraction (NCF) was lower than 35% by mass, NCF had an insignificant effect on −ds/dσv−modified (equal to 1). By contrast, in the case of higher NCF (>35%), −ds/dσv−modified became lower than 1, and the higher the NCF, the lower the −ds/dσv−modified value. These findings provide useful information for better understanding the mechanism involved at the microstructure level in the stress/suction coupling during stress release in clayey soils. [ABSTRACT FROM AUTHOR]

Recently, permeable geotextile tubes in conjunction with prefabricated horizontal drains (PHDs) have become increasingly popular for dewatering high water content slurries or sludge. However, how to analyze the consolidation process of the sludge in the geotextile tube so as to provide a proper design and prediction becomes a technical challenge. In this paper, we have proposed a two-dimensional plain-strain consolidation model for sludge consolidation in a geotextile tube under combined fill and vacuum preloading. A semi-analytical solution was obtained and validated through experimental observations. A salient finding of this study is the identification of a critical condition at which the optimum consolidation efficiency is achieved. Consolidation efficiency decreases gradually beyond this critical condition, which arrives later as the PHD pave rate and element height to width ratio increase. Furthermore, this analytical method clearly shows how preloading affects the dewatering process and the effect of fill surcharge is more pronounced than that of vacuum preloading of the same magnitude, owing to the vacuum attenuation and leakage. [ABSTRACT FROM AUTHOR]

The response of sands stabilized with colloidal silica aqueous gel is investigated in the laboratory. The role of colloidal silica on subsequent sand behavior is examined with the aid of monotonic and cyclic loading tests so as to establish the mechanical response of the treated sand. Depending on the loading conditions when the strength of the treated sand is enhanced and liquefaction is averted, its stiffness may reduce and its compressibility increase. This contradictory behavior is investigated on the basis of an extended database including direct shear, triaxial, and normal compression tests. Initial stiffness is lower for treated sand compared with untreated sand under drained and undrained monotonic loading conditions. It is demonstrated that only dense treated sand shows similar stress-strain properties with the untreated sand under cyclic loading, whereas loose treated sand accumulates strain and excess pore-water pressure much faster than the untreated sand. The critical state line applying to the treated sand lies substantially above that manifested by untreated sand. The two lines converge as the stress level increases to around 2,000 kPa. [ABSTRACT FROM AUTHOR]

Recent earthquake events have indicated that liquefaction histories can greatly affect the reliquefaction resistance of saturated sandy ground. This paper reports a fundamental experimental study of medium-dense/dense Toyoura sand with a relative density of 70% using a hollow cylinder torsional shear apparatus (HCTSA) to provide a better understanding of the integrated effects of strain history and soil fabric on reliquefaction resistance of Toyoura sand. A series of postliquefaction monotonic tests was conducted to investigate the degrees of induced fabric anisotropy at different states of liquefaction and subsequent reconsolidation. A series of reliquefaction tests was performed on sandy specimens that had experienced medium to large residual shear strains (γres) and that had reconsolidated in different states, under various cyclic stress ratios (CSRs). It was shown that reliquefaction resistance of Toyoura sand is influenced highly by the residual shear strain during liquefaction and fabric anisotropy after reconsolidation. The experimental results were used to predict excess pore-water pressure (EPWP) buildup during liquefaction and reliquefaction as a function of shear strain or dissipated energy. The liquefaction/reliquefaction resistance of Toyoura sand was quantified using an energy-based criterion considering the integrated effects of strain history and soil fabric. [ABSTRACT FROM AUTHOR]

In geotechnical tests, a thin layer of lubricants is usually applied along interfaces between tested soils and the sidewall of a container to minimize interface friction (shear strength). The effectiveness of lubricants in reducing the interface friction has not yet been fully evaluated. In this paper, the effectiveness of several commonly used lubricants in reducing the sidewall friction is presented through backfilling and stress measurement tests performed in a lightly instrumented column. The interface friction angles are back calculated from the measured stresses, using an arching analytical solution. The results show that the most efficient among the tested lubricants is a combination of Teflon and silicone grease, which can reduce the interface friction angle to 16.8°, a value far from being qualified as negligible. For most cases, the application of lubricants has little or no effect in reducing the sidewall friction. For some cases, the application of a lubricant material can even increase the sidewall friction angle. To verify these somehow surprising results, direct shear tests were performed to obtain direct measurements of the interface friction angles between the tested sand and the tested lubricant materials. Very small normal stresses were applied and the sand was gently placed in the shear box to imitate the testing conditions of column filling tests. The good agreement between the directly measured and back-calculated interface friction angles indicates that the column tests and the back-calculated results are reliable. Further analysis reveals that the small cohesion of lubricant materials can become negligible under a high stress state. Under a low stress state, this small cohesion can be translated into high friction. It is concluded that the tested lubricants may be efficient under high stress conditions, but not efficient under low stress conditions. For the latter case, the consideration of zero sidewall friction between the tested soil and lubricated sidewall of the container can lead to inaccurate and even totally wrong results. [ABSTRACT FROM AUTHOR]

Liquefied soils are considered as soils devoid of any strength or having only limited strength. Post-liquefaction shear behavior of soil before the drainage of excess pore pressure is important in predicting the immediate performance of foundation and soil structures subjected to liquefying loads. In the present study, the post-cyclic undrained behavior of weathered silty sand was examined under triaxial test conditions. The soil showed complete strength recovery after subjecting it to monotonic shearing up to large strains. The post-liquefaction shear behavior was mostly determined by the amount of excess pore pressures that developed during cyclic loading. The cyclic load amplitude and shear strain did not seem to have an effect on the post-cyclic shear behavior. Post-cyclic shearing showed that with sufficient strain the soil recovered its original strength even without dissipation of any excess pore pressure. [ABSTRACT FROM AUTHOR]

Glacial tills are widespread across North America, northern and central Asia, and northern Europe, where they are also found under the Baltic, North, and Norwegian Seas. Their geological and geotechnical characterization is important to a wide range of onshore and offshore engineering projects. One aspect of tills on which little has been reported is their mechanical anisotropy. This paper reports coordinated hollow cylinder apparatus (HCA) tests, triaxial shearing, and small-strain stress probing experiments, supported by index testing, on high-quality samples of natural low-to-medium plasticity, high overconsolidation ratios (OCR) stiff clay-till from the Bolders Bank Formation at Cowden, near Hull in the UK. Material variability and sampling bias are inevitably introduced by the till's erratic gravel particles and fissure systems, and these aspects are addressed carefully. The experiments investigated the till's stiffness and shear strength anisotropy from its limited linear elastic range up to ultimate failure, showing that stiffnesses are higher in the horizontal direction than in the vertical and that higher undrained shear strengths develop under passive horizontal loading than active vertical loading. Comparisons are made between the till's patterns of anisotropy and those applying to previously studied sediments, and reference is made to in situ stiffness measurements. The important implications of anisotropic behavior for geotechnical design and the interpretation of field tests are emphasized. [ABSTRACT FROM AUTHOR]

Deep and high-stress mining relies on backfill to support exposed host rock surfaces, but the backfill response to isotopic compression is virtually unknown. This paper studied the properties and behavior of a cemented paste backfill (CPB) for different cement contents (CCs) and specimen curing times (CTs), for isotropic stresses up to 6.5 MPa. The isotropic compressive behavior was characterized by an initial linear elastic preyield response quantified by the bulk modulus and a linear inelastic postyield response at high stress. The results showed that the postyield compression line loci depend on cement content and curing time of CPB, and fitting functions were determined to predict this evolving behavior based on cement content and specimen cure time. The results could form the basis for developing and calibrating the isotropic compression hardening laws for future constitutive models. [ABSTRACT FROM AUTHOR]

This paper compares experimental results on the stabilization of clayey dredged material (DM) using quicklime (QL), hydrated lime (HL), portland cement (PC), and Class F fly ash (FA). The DM was a clay, high-plasticity soil, dredged from the US Army Corps of Engineers Port Arthur (USACEPA) facility along the Neches River located in Orange and Jefferson Counties, Texas. The soil consists of a large proportion of clay (66%), has high moisture limits (plasticity index: PI = 52 and liquid limit: LL = 80), and is characterized as a fat clay with silt. Physical properties of the untreated DM, such as unconfined compressive strength (UCS), consistency limits, and compaction behavior, were determined. Stabilizing reagents were mixed in various percentages by dry weight of DM. Results indicate that 12% QL, 6% HL, 6% PC, and 7.5% Class F FA by dry soil weight must be used to meet a minimum benchmark criterion of a PI value below 35, which was established based on Texas Department of Transportation (TxDOT) specifications. Standard compaction tests were carried out in accordance common standards with ASTM D698 to determine the optimum moisture content (OMC) for all mixtures. Stabilized mixtures were prepared at the corresponding OMC, and unconfined compressive tests were run according to common standards. Tests results were compared with the relevant literature, and a linear regression model was developed to predict the PI reduction as a function of initial PI, LL, and stabilizer type and content with good accuracy (R2 = 0.86). Overall, tests showed that stabilization of clayey DM using lime products, PC, or FA significantly improved the DM physical properties, which could then potentially be used as a local fill construction material that is cost-effective and environmentally friendly and reduces the overall use of cement products. [ABSTRACT FROM AUTHOR]

Adding discrete fibers to soils can improve their strength; however, fiber reinforcement remains scarce in practice. Previous studies on the performance of soils reinforced with discrete fibers consist mainly of laboratory studies with either clay or, most often, uniform sand as the host soil, so there is a lack of data on other types of soils such as weathered soils, which tend to be well graded. Unlike uniform soils, which are generally dilative, well-graded soils usually show a contractive behavior. This study examines the effect of adding fibers to a completely decomposed granite (CDG) typical of many residual soils, which has the characteristics to be sensitive to material and sample preparation and also to be compressive during shearing. It is found that adding discrete fibers to the CDG homogenizes it because the reinforced soil is not sensitive to the method of material or sample preparation. It is also found that, despite its compressive nature, fibers mobilize extra strength compared with the unreinforced soil, and this effect does not reduce at large confining stresses. [ABSTRACT FROM AUTHOR]

Rutting or permanent deformation is one of the severe distresses manifested in flexible pavements caused by the various mechanisms such as densification, lateral plastic flow, and/or loss of materials under wheel path due to repeated heavy traffic loads. Various laboratory tests have been devised to determine the rutting propensity and to optimize the field performance of hot mix asphalt (HMA) mixtures as a part of the HMA mix and structural design processes. Although various approaches exist to predict the permanent deformation of HMA, this study develops a relationship of flow number (FN), dynamic modulus (DM), and uniaxial repeated-load permanent deformation (RLPD) to enable the trade-off analysis among them. Also, a novel parameter, FN index, is explored and used to determine the rutting potential of HMA mixtures. Twelve globally practiced HMA mixtures are investigated with three different performance grade binders and single limestone aggregate source. Superpave gyratory compacted specimens are subjected to performance testing (FN, DM, and RLPD) and results indicate a strong correlation of FN index with DM and exhibit better correspondence than the traditional FN (cycles) parameter. [ABSTRACT FROM AUTHOR]

In the present study, a new physically sound approach to experimentally obtain the contribution of each complex pier component to the ensemble scour depth is presented and illustrated. The new approach can be assumed to take into account the interactions of the different flow structures and their impact on the local scour depth. A total of 67 long-duration tests were performed to quantify those contributions according to the new approach, 35 of which were run in the scope of this study. Results showed that the contribution of each component is highly dependent on its position relative to the initial bed level and on the pier geometry. The experimental results obtained through the new approach were compared with the predictions of two widely accepted methods, showing that these tend to implicitly disregard interactions and joint effects of the different complex pier components with or on the flow structure. [ABSTRACT FROM AUTHOR]

Horizontal-ellipse culverts have been used for many years as a substitute for more conventional short-span bridges; however, their performance has never been evaluated experimentally. This paper describes an experimental program to understand the behavior of a horizontal-ellipse culvert during backfilling, when subjected to simulated service loading at the ground surface, and during an ultimate limit states test. The backfill response of the specimen was similar to circular culverts except that, as expected, the specimen exhibited lower vertical stiffness than horizontal stiffness due to its shape. Contrary to current design conventions, the response of the culvert to surface loading was influenced by the cover depth. At 0.9 m of cover, the load-carrying mechanism was ring compression, whereas at 0.45 m, significant bending stresses developed in the top of the pipe. At 0.45 m of cover, the ultimate capacity of the culvert was measured as a tandem axle load of 1,324 kN. Although this is approximately twice the fully factored design load, the culvert failed after the development of a plastic hinge mechanism instead of the wall compression considered in American and Canadian design codes, although the structure still had reserve capacity. [ABSTRACT FROM AUTHOR]

Physico-chemical effects have a significant impact on the behavior of clay barriers due to the interactions between the pore fluid and clay particles, and they pose a great challenge because the efficiency of clay barriers and cover systems may be altered. Therefore, this paper highlights the effect of physico-chemical factors on shrinkage behavior of compacted expansive clay. To achieve this, the compacted clay specimens were inundated with distilled water, NaCl, and CaCl2 salt solutions in separate oedometer cells at a vertical pressure of 6.25 kPa and allowed to swell. The swollen specimens were gradually shrunk until the specimens attained constant mass, and the changes in void ratio and water content were monitored during drying. The experimental results showed that magnitude of induced osmotic suction and type of pore fluid had a significant impact on shrinkage behavior of compacted clay specimens due to the changes in soil structure. The average pore size of compacted specimens significantly decreased with the induced osmotic suction due to the reduction in size of micropores owing to the suppression of double layers. The discussions are supported by scanning electron microscopy images. Also, the experimental shrinkage data were fitted using modified van Genuchten and Fermi mathematical models, and the results showed that these models fit well with an adjusted R² higher than 0.9962. [ABSTRACT FROM AUTHOR]

At present, bridges are frequently built with geometries that consist of a column founded on a pile cap and supported by an array of piles, referred to as common complex piers or most often (as also in this paper), briefly, as complex piers. This paper addresses prediction of local scour depth at those complex piers. An experimental campaign of 48 long-duration tests was performed with seven complex pier models under steady clear-water flow conditions to quantify the influence of the relative column width, Dc/Dpc (Dc = column width, Dpc = pile cap width), the relative pile cap thickness, T/h (T = pile cap thickness, h = approach flow depth), and the pile-group configuration on the equilibrium scour depth, dse. Several tests were carried out for the possible range of variations in the pile cap position relatively to the initial bed level. The values of dse were estimated by extrapolation of the experimental data series. The performance of three methods, i.e., Auckland, HEC-18, and Florida Department of Transportation (FDOT), to predict dse is analyzed and discussed. Based on the experimental results of the present study and on the conceptual approaches of Auckland and FDOT methods, an alternative formulation for a predictor of dse at (common) complex piers is suggested and validated. [ABSTRACT FROM AUTHOR]

Step-pool systems occur naturally in steep mountain streams and as man-made structures in steep channel sections where they serve as energy dissipating structures. Three different flow regimes may occur. The dominant flow regime is the cascading “nappe flow regime.” At higher discharges the “skimming flow regime” develops with an almost plane water surface. In between these flow regimes a “transition flow regime” occurs. A physical model was used to measure the pressure distribution around a single step for a particular step-pool geometry and for different flow regimes (nappe/transition/skimming). To achieve this, 14 simultaneously recording piezoresistive pressure transducers were distributed around the step. The results showed that the regime change from nappe to transition flow is associated with a discontinuity of the average Froude number of a step-pool unit as well as drops in pressures and water depth. Relative instantaneous drag forces reached a maximum for this regime change. This implies that the regime change from nappe to transition flow is a critical loading case with respect to the stability of the steps. On the other hand, the mean drag forces showed little systematic variation as the flow rate changed with a large spread in results for measurements repeated at the same flow. Thus, for the nappe and transition flow regimes, the mean drag force is not a good criterion to use to predict step stability. The occurrence of the different flow regimes could be related to the average Froude number of a step-pool unit. The results have practical implications for the design of step-pool systems. [ABSTRACT FROM AUTHOR]

Rheological characteristics are one of most important properties needed to be considered in the design and construction for the long-term stability and serviceability of underground structures in the rock mass. To date, although extensive studies on the rheological properties of rocks are available in the literature, most of the existing studies reported the strain-time data for the axial deformation through the compression rheological method and did not mention the lateral deformation, and mainly focused on the soft rocks at shallow depth. Thus, very limited attention has been paid to the rheological properties of deep and hard rock, neglecting the effects of structural anisotropy on the rheological properties. This paper presents a comprehensive, in-depth study of the rheological behaviors of super-deep hard rock, considering the effects of structural anisotropy by using the uniaxial and biaxial creep tests. The results revealed that significant creep behavior can be observed in the hard rock specimens under high stress in the in situ conditions, and the strain-time behavior of hard rock exhibited brittle failure. The strain-time curves of hard rock exhibited two obvious phases of instantaneous creep and steady-state creep, without the phase of accelerated creep. Moreover, it was observed that the rheological behaviors, including the instantaneous modulus, transient creep duration, axial and lateral creep deformations, steady-state creep rate, volumetric strain, and contraction ratio are strongly affected by the structural anisotropy. Based on the experimental data, empirical models of the parameters governing creep behavior have been established. [ABSTRACT FROM AUTHOR]

Scour protection around hydraulic structures in fluvial, estuarine, and coastal waters is an essential component of a meaningful and durable design. The continuous optimization of scour protection systems and design approaches leads to faster and more cost-effective construction processes. Although scour protection now often consists of a two-layer design, approaches that incorporate only one layer depict a major step forward. Therefore, this research focuses on the stability of a wide-graded quarry-stone mixture consisting of crushed granodiorite (Jelsa quarry, Norway) with fractions ranging from 0.063 to 200 mm. The material was exposed to an incrementally increased unidirectional current in a closed-circuit flume. The induced flow field and leading parameters were measured at various positions horizontally and vertically, whereas the erosion rates were determined behind the test bed specimen.With increasing flow velocity the development of a static armor layer was observed at the bed surface. Bed-shear stresses were determined to be strongly variable across the rough test bed. Fractional critical shear stresses indicate highly selective mobility of individual fractions. Least-square fitting of the determined critical shear stresses based on the dimensionless reference grain size di=dΨ (with dΨ as the product of the geometricmean size dg and the geometric standard deviations g) is suitable for describing the stability behavior of the investigated material. [ABSTRACT FROM AUTHOR]

An alternative approach to replacing corrugated steel culverts is to insert a new pipe inside the existing culvert and grout the space between them, a process known as sliplining. Though sliplining is a preferred rehabilitation approach among departments of transportation, very little research has been done to investigate the capacity enhancement provided by sliplining and how the load is shared between components in a sliplined culvert (i.e., the existing pipe, the liner, the grout, and the surrounding soil). A series of experiments was conducted on a deteriorated corrugated steel culvert at two different burial depths (600 and 900 mm) under surface loading before and after the culvert was rehabilitated with a grouted high density polyethylene (HDPE) slipliner. The rehabilitated culvert was found to be considerably stiffer and the diameter changes under surface load were reduced by more than 90% compared with the unrehabilitated culvert suggesting that the negative arching between the pipe and the soil has increased. The strains in the existing pipe were also reduced by more than 70% with negligible strain being measured in the invert of the culvert where the corrosion was concentrated. The results also indicated that when a neat grout with a compressive strength of approximately 30 MPa is used (what could be considered to be high strength in comparison with low density grouts featuring entrained air), the existing pipe and the grout carry most of the load, and the liner's main role is to improve the hydraulic conductivity. Additionally, because of the increased stiffness of the rehabilitated pipe, the surrounding soil carries less of the surface load applied above the pipe. [ABSTRACT FROM AUTHOR]

An experimental campaign of 25 long-duration (13-47 days) laboratory tests was carried out with three complex pier models under steady clear-water flow conditions. Each model, characterized by a different relation between the column and the pile-cap widths, Dc/Dpc, was tested for a variety of pile-cap positions relatively to the initial bed, Hc. The experimental data were used to describe the temporal evolution of the scour depth as a function of Hc/h (h = approach flow depth). The common criterion to stop experimental tests on complex piers was analyzed, and a new criterion was introduced. The equilibrium scour depth, dse, was calculated by extrapolation of data series. The results are used to evaluate the effect of Dc/Dpc and Hc/h on dse when the pile cap is above the bed (Situation 1), partially buried in the bed (Situation 2), and completely buried in the bed (Situation 3). The analysis includes the definition of Hc at which the maximum dse occurs through an equation that takes into account the Dc/Dpc ratio, the relative pile cap thickness, T/h, and the column and pile-cap shapes. [ABSTRACT FROM AUTHOR]

Current bubble oil booms (BOBs) create bubble curtains to protect fixed installations in calm waters such as harbors, but fail in more energetic environments. Field and lab studies reveal that area bubble plumes enable BOB applications in such environments. Area bubble plumes exhibit dynamics distinct from point- or line-source plumes, including thicker and more robust outwelling flows and relatively smaller turbulence scales. Area bubble plume studies broaden our understanding of natural systems, where currents and waves are ubiquitous, leading to a variety of marine applications. Laboratory studies in a large flume have investigated the fluid dynamics of shallow line and area bubble plumes. These studies focused on area-plume application to oil spill response, which, based on preliminary tests, featured improved outflows with a downstream barrier. A range of ambient currents, current-plume angles, and airflows were tested. Key to understanding current-plume interactions was the upstream rotor or near-surface recirculation vortex. The strongest outwelling was for a 0:25 ms-1 current and 5-sparger plume (~unity width-to-depth aspect ratio, ε). Owing to acceleration by the rotor, however, the rotor collapsed into this plume at a current of 0:40 ms-1, destroying plume coherency. The fastest surface outwelling was slightly outside the bubble plume edge, and horizontal profiles were well described by two piecewise exponentials. A 10-sparger plume with ε~2 was slower but more robust (thicker), allowing its rotor to survive in stronger currents. Vertical profiles of the outwelling flow were well described by an offset Gaussian (subsurface peak) with significantly lower velocity fluctuations than for line-source plumes. Streamline convergence from the rotor was important in reducing turbulence fluctuations. Oblique angle currents led to greater rotor acceleration with the surface outwelling flow largely perpendicular. However, velocities deeper than the main outwelling flow were deflected downstream, showing a highly nonlinear, helical flow in the rotor. These results highlight the importance of better understanding the complex flow fields of area bubble plumes in natural systems and marine engineering applications. Better characterization of the rotor is needed for a range of ambient conditions to enable BOB design optimization. [ABSTRACT FROM AUTHOR]

When dredging in sensitive environments, efforts have to be made to limit the free dispersal of suspended fine sediment from the dredging spill. The use of hanging silt curtains as an environmental mitigation measure is especially widespread. Despite frequent application, their ability to reduce turbidity levels through vertical diversion of sediment-laden currents remains the subject of debate. This paper addresses a series of laboratory measurements and numerical model simulations to determine the efficiency of hanging silt curtains, defining a new efficiency parameter. The model was validated against the laboratory experiments. Model simulations focusing on vertical diversion of the sediment-laden current suggest that hanging silt curtains do not have a favorable influence on the settling of suspended sediment when applied in crossflow. The diversion of currents underneath the curtain causes flow separation and intense turbulent mixing, which counteracts settling of suspended sediment particles. The results imply that the widespread application of hanging silt curtains should be reconsidered from a physical point of view. [ABSTRACT FROM AUTHOR]

In a Latin American context, few studies exist regarding the construction of churches during the colonial period using adobe and rammed-earth techniques. Investigations of their spatial characteristics, systems of construction, and structural behavior, therefore, are also scarce. This lack of research has led to poor results in restoration attempts for these kinds of churches, which has caused the loss of important Colombian architectural and historical heritage. Additionally, Colombia is at a high seismic risk, and adobe and rammed-earth buildings are particularly vulnerable during earthquakes. This paper presents the results of an investigation of these kinds of structures, developed by the investigative groups investigation group on materials and structures (GRIME) and Estructuras & Construcción (at Pontificia Universidad Javeriana) during the period 2002-2013. The investigation focuses on churches in the geographical area within the central Colombian highlands built during the 16th and 17th centuries. The study takes an architectural and historical approach coupled with structural laboratory work (involving shake table tests on 1:50 models), where the authors applied a reinforcement alternative with confinement wood elements to improve the seismic performance of the structural system of rammed-earth churches. According to these results, the use of confining wood elements as reinforcements reduces the relative displacement induced by earthquakes to doctrinal earth-built churches and diminishes the propagation of cracks. [ABSTRACT FROM AUTHOR]

This paper presents a hydrodynamic experiment that examines the wave forces acting on the superstructure of coastal highway bridges to gain insight into the mechanical characteristics of the wave forces caused by the combination of storm surges and huge waves. The experiment is unique in that the specimen is a full bridge model, including its superstructure, substructure, and neighboring segments. After introducing the experimental setup and test program, this study analyzes the quasi-static and slamming components of the vertical wave force, the horizontal wave force of the superstructure in different clearances, wave heights, and wave periods. The test results are subsequently compared with two theoretical models suggested by Douglass and AASHTO guidelines to provide the experimental validation of those models. By comparing the test results and the existing models, a number of observations and discussions are produced to improve the accuracy of those theoretical models further. [ABSTRACT FROM AUTHOR]

Based on an extensive testing program, this study presents the mechanical behavior of a lightweight expanded clay aggregate (LWA). This material is currently being used in many civil engineering works and particularly in geotechnical applications due to its low weight, high shear strength, and favorable drainage characteristics. The present investigation is based on a particulate mechanics approach aimed at the quantification of appropriate model parameters in order to describe the material's mechanical performance. The first part of the study concentrates on the determination of the physical and mechanical properties of the particles themselves. Relevant hydro-mechanical aspects of the particulate material are investigated. The second part focuses on the mechanical behavior of the aggregates. Using the compaction characteristics and stress ranges prescribed by the product manufacturer, a series of laboratory tests was performed on materials with two different grain-size distributions and water content conditions. The results obtained in the first part contributed to the determination of a phenomenological interpretation of the mechanical behavior of the aggregate. Finally, the quantification of nonlinear stiffness, internal friction angle, and its dependency on normal effective stresses and K0 for the design of civil engineering works is presented. This research also offers relevant support for the development of constitutive models. [ABSTRACT FROM AUTHOR]

As buried infrastructure in North America and around the world reaches the end of its service life, engineers and infrastructure managers will require an improved understanding of the performance of both deteriorated pipes and repair techniques. To develop this improved understanding, sensing technologies that enable the full pipe behavior to be measured, rather than a small number of localized discrete measurements, are required. A possible solution to this problem is to use distributed fiber optic strain sensors. To this end, a series of buried pipe tests were undertaken on steel, concrete, and high-density polyethylene (HDPE) pipes instrumented with distributed fiber optic strain sensors. The distributed measurements were in agreement with conventional strain gauges, but enabled the full strain distribution around the circumference of the pipe to be measured. This allowed localized behavior that would have been missed with conventional strain gauges to be detected and quantified. In addition, the choice of fiber optic cable proved to be an important consideration due to a trade-off between measurement accuracy and sensor robustness. [ABSTRACT FROM AUTHOR]

As infrastructure built during the 20th century reaches the end of its service life, engineers and managers are increasingly turning to rehabilitation rather than replacement to potentially reduce costs. For corrugated steel pipes and culverts, one such rehabilitation alternative is to use slip lining where a liner (new pipe) is placed inside the existing deteriorated pipe and the space between them is grouted. The current research seeks to better understand the performance of slip-lined systems by (1) characterizing the properties of a low-strength and a high-strength grout; (2) conducting a series of pipe tests to determine the load-carrying capacity and stiffness of a corrugated steel pipe and pipes that have been rehabilitated with slip liners; (3) understand the impact of grout strength and the liner on pipe stiffness and strength; and (4) determine the level of composite action in the pipe system by using a plasticity approach to estimate the load-carrying capacity of the system. The pipes rehabilitated with low-strength grout had increased strength (three times greater) and stiffness (eight times greater) versus an unrehabilitated pipe, whereas the specimens rehabilitated with high-strength grout showed higher increases in both load-carrying capacity (ten times greater) and stiffness (50 times greater) over the unrehabilitated pipe. The high density polyethylene (HDPE) liner had no impact on the load-carrying capacity of the specimens with high-strength grout and required large diameter changes to enhance the load-carrying capacity of low-strength grout specimens. A plasticity approach was used to estimate the load-carrying capacity of the specimens and indicated that for these tests, composite behavior between the grout and the corrugated steel pipe was developed. [ABSTRACT FROM AUTHOR]

This study presents the experimental results for seven different tests carried out on high-density polyethylene (HDPE), PVC, and metal pipes with medium-size diameters. The main objective of the experimental program is to evaluate and characterize, under laboratory conditions, the performance and mechanical properties of the various flexible pipes considered in the study. The diameters of the pipes studied are 36 in. (914 mm) and 48 in. (1,219 mm). The laboratory tests conducted are the simple-beam test, parallel-plate test, flattening test, curvedbeam test, joint-integrity test, and tensile test, as well as an environmental stress-cracking test. The results of the tests are presented in terms of load-deflection relations, load versus longitudinal and transverse strains, failure modes, and pipe stiffness. The test results indicate that HDPE and PVC pipes show good performance compared with metal pipes. In addition, the experimental results for flexible pipes meet AASHTO specifications. The HDPE and PVC pipes tested according to the ASTM and AASHTO Standards show pipe stiffness values higher than the minimum specified by the standards. The pipe stiffness values of the HDPE specimens based on the curved-beam test are two to three times greater than those based on the parallel-plate test. It was found that for a given vertical deflection, the HDPE pipe stiffness substantially increased with an increase of loading rate. [ABSTRACT FROM AUTHOR]

This paper focuses on nonlinear creep behavior with a consecutively decreasing creep coefficient Cae fully related to the soil density. Conventional oedometer tests on reconstituted samples of several natural soft clays are selected to clarify the evolution of creep coefficient throughout testing. On this basis, a simple nonlinear creep formulation is proposed accounting for the effect of volumetric packing of soil assemblies. The formulation is then incorporated into a newly developed elastic-viscoplastic model to take into account the nonlinear creep of natural soft clays. One additional parameter is added that can be determined in a straightforward way from an oedometer test without additional experimental cost. The enhanced nonlinear creep model is examined by simulating a conventional oedometer test on reconstituted Haarajoki clay. The improvement of predictions by the nonlinear creep formulation is highlighted by comparing predictions with constant Cae. The enhanced model is further applied to Murro test embankment. The influence of consideration of nonlinear creep on the embankment behavior is discussed. [ABSTRACT FROM AUTHOR]

Long and torsionally slender H-shaped cross sections, often used as tension members in truss bridges, can exhibit wind-induced torsional motions. These motions have produced high-cycle fatigue damage for some bridges. There is limited information available to evaluate the torsional response on the fatigue performance of themembers and connections. An in-service bridge with a documented history of wind-induced torsional motions in the verticals was instrumented to capture the wind speed and direction that induced torsional motions in the verticals. Sensors also captured the rotation angle amplitudes and numbers of cycles. Laboratory tests were conducted on a full-size replica of a vertical-and-chord connection to establish the relationship between rotation and normal stresses in the cross section from warping restraint at the connection locations. Analytical methods were shown to accurately predict the rotations and warping stresses along the member length. Applying the experimental and analytical results, the stress ranges were determined for the field-measured torsional responses, and the fatigue potential was evaluated. The results showed the measured stress ranges are near the constant amplitude fatigue limit, but the large cycle counts and frequency of events in the historical wind record that could produce torsional response indicate the need for continued monitoring and a long-term mitigation strategy. [ABSTRACT FROM AUTHOR]

The dynamic modulus of asphalt concrete mixtures is a key property in assessing asphalt pavement performance based on its role in the mechanistic-empirical design method. The dynamic modulus is also considered to be used as one of the major characteristics in performance-related specifications for quality assurance. However, no feasible method to estimate the mean and variance of the in-place dynamic modulus for the as-built asphalt pavement has been suggested. This paper presents a methodology of stochastically evaluating the in-place dynamic modulus of the as-built asphalt pavement using a relationship of in-place air voids and a set of single dynamic modulus values measured in the laboratory. The methodology was validated with asphalt mix collected from a construction site. The comparison plot between the estimated in-place dynamic modulus and as-designed asphalt mix demonstrated a simple way to evaluate the as-built mix quality. This methodology provides several practical advantages to determine the quality of as-built mix compared with that of as-designed mix in terms of the dynamic modulus. In addition, the methodology envisions the possibility of incorporating the dynamic modulus into performance-related specifications. [ABSTRACT FROM AUTHOR]

This study proposes a laboratory-scale experimental setup that simulates the dynamics of a full-scale stay cable with a transverse damper, allowing the full-scale performance of different types of dampers to be evaluated and compared in a laboratory setting. This test scheme resembles hybrid testing in that it retains the physical structural component for experiments, whereas it uses an equivalent model to represent the large-scale main structure instead of the numerical simulation used in a hybrid test. For the cable, a feasible model is presented that is composed of two flexible beams that are suspended vertically, fixed at their upper ends, and connected at their lower ends by a rigid mass; the damper is attached transversely to one of the beams. The setup is modeled as tensioned beams for clamped-guided supports with a terminal mass and an intermediate damper for dynamic analysis, and the characteristic equation is formulated from dynamic-stiffness matrices of beam segments. Modal properties of the setup are found to be similar to those of a cable-damper system, based on which the equivalence conditions are presented. The established equivalence between a cable and a model is further found to be roughly independent of damper properties for practical applications, therefore ascertaining the potential of this setup for a cable-damper study. Experiments have also been conducted in which the damper performance is evaluated on a fullscale cable and on a beam-mass assembly designed to represent the first vibration mode of the stay cable. The amplitude-dependent damping ratios achieved in the laboratory setting are found to be comparable to those achieved for the full-scale cable, suggesting the applicability and effectiveness of this experimental setup. [ABSTRACT FROM AUTHOR]

The response of physical models of beach profiles to random breaking waves was studied to investigate size-selective sediment transport and cross-shore profile evolution. Three types of beach profiles with different sediment mixtures were considered and subjected to waves until profiles reached equilibrium. Size-selective sediment transport was evident in the experiments, with the mean sediment size varying up to 20% along the beach profiles. Consistent coarsening and fining of the surface sediment in the experiments revealed size-selective sediment transport governed by cross-shore variations in energy dissipation, affecting important beach profile features such as sandbar structures and offshore and foreshore slopes. The theoretical basis of the transport phenomenon was described by analyzing the relationship between the transport processes and essential wave and hydrodynamic parameters obtained using a new set of numerical models. The results showed that beach profile changes and associated sediment grain sorting are most sensitive to instantaneous total water velocity and local energy flux under propagating waves. [ABSTRACT FROM AUTHOR]

This paper presents optical measurements of debris movement and tsunami inundation over an unobstructed beach in a laboratory wave basin. The debris consisted of rectangular boxes and was placed unconstrained on a flat section raised above the basin floor with no still water on the raised section. Debris movement was measured using two overhead video cameras and a novel object-tracking algorithm. Two standard optical techniques, wave edge detection and particle image velocimetry, were used to compare optical and in situ measurements of fluid velocity. The debris motion (position, velocity) in the onshore direction was found to be repeatable, but the offshore motion varied between trials because of the irregular nature of the flow field during the return. For debris in free translation, as the number of debris specimens increased, the peak average velocity decreased and the onset of the peak was delayed in the onshore direction. In the offshore direction, the velocity was lower by a factor 4-6 and was independent of the quantity of debris. The decrease in the peak onshore velocity with increasing amount of debris was observed for debris that undergoes an initial rotation. The peak onshore velocity was nearly independent of whether the initial motion was purely translational or a combination of rotation and translation. [ABSTRACT FROM AUTHOR]

Compensation grouting is often employed as a mitigation technique to reduce the settlements induced by tunneling. The efficiency of compensation grouting, defined as the ratio of the volume of heave induced at the ground surface to the volume of injected grout, is strongly dependent on grout properties, injection characteristics, and soil properties. In clayey soils, site observations and laboratory tests show high values of compensation efficiency immediately after injection. However, the efficiency can decrease with time if positive excess pore-water pressures develop in the soil during the injection process. Conversely, in sandy soils, a loss of volume occurs because of pressure filtration of the grout during and soon after the injection process, which reduces the compensation efficiency. This paper describes an analytical model that can be used to evaluate the volume loss produced by pressure filtration of cement-bentonite grouts as a function of soil, grout, and injection parameters. The magnitude of pressure filtration is evaluated as the grout efficiency, which is given by the ratio of the volumes of the final grout body to the injected grout. Results show that the grout efficiency increases with decreasing soil permeability and with increasing grout bentonite content. The result of a grout injection test on a silty soil is back-analyzed using this approach in which the grout efficiency is first evaluated through the proposed filtration model and then used to calibrate a numerical simulation of the test. The good agreement between experimental data and computed results shows that prediction of the efficiency of compensation grouting can be improved using the proposed approach. [ABSTRACT FROM AUTHOR]

The overburden correction factor () is used to account for the curvature of the cyclic strength envelope with increasing consolidation stress, and it provides part of the basis for extrapolation of liquefaction-triggering correlations based on standard penetration test (SPT) and cone penetration test (CPT) to larger depths than covered by current databases of liquefaction case histories. This paper presents an updated database of laboratory test results defining effects. Laboratory test results included in previous databases are reexamined in light of current understanding of factors that can affect laboratory measurements of cyclic strengths, including the effects of increasing density with increasing consolidation stress, variable overconsolidation ratios, and other factors. The updated database is used to examine potential biases in the relationships used in two SPT-based liquefaction triggering procedures. The first relationship was found to be conservative with respect to the data for clean sands and less conservative for sands with fines contents between 7 and 35%. The second relationship was found to provide a reasonably good fit to the data for clean sands and to be slightly unconservative for sands with fines contents between 7 and 35%. Implications for practice are discussed. [ABSTRACT FROM AUTHOR]

Gene expression programming (GEP) models, a robust variant of genetic programming, are developed in this study to correlate resilient modulus with routine properties of subgrade soils and state of stress for pavement design applications. A database used for building the model was developed that contained grain size distribution, Atterberg limits, standard Proctor, unconfined compression, and resilient modulus results for 97 soils from 16 different counties in Oklahoma. Of these, 63 soils (development data set) are used in training, and the remaining 34 soils (evaluation data set) from two different counties are used in evaluation of the models developed. Two different correlations were developed using different combinations of the influencing parameters. The proposed constitutive models relate the resilient modulus of routine subgrade soils to moisture content , dry density , plasticity index (PI), percent passing a No. 200 sieve (), unconfined compressive strength , deviatoric stress , and bulk stress . The results are compared with those from artificial neutral network (ANN) models. Overall, GEP models show good performance and are proven to be better than ANN models. The GEP-based design equations can be readily used for pavement design purposes or may be used as a fast check on solutions developed by more in-depth deterministic analyses. [ABSTRACT FROM AUTHOR]

Foamed asphalt binders are increasingly being used to produce warm mix asphalt. This paper presents the findings from a study conducted to (1) identify a repeatable and accurate method to characterize the quality of asphalt binder foams, and (2) use this method to evaluate the influence of water content, binder type, and foaming device on the quality of foamed binders. Laser and ultrasonic distance-measuring tools were used in combination with digital imaging of the foamed surface to quantify and better understand the expansion and decay of foamed asphalt binders over time. Measurements obtained from these methods were used to evaluate the extent and stability of foams produced using three different asphalt binders at three water contents and two laboratory foaming devices. Rheological properties and moisture content of selected binder residues were also measured. Results indicate that both the laser- and ultrasonic-based methods were promising in terms of their ability to provide a repeatable and detailed history of the change in volume of the foamed asphalt binder as the foam collapses. It was also shown that water content and binder type have a significant influence on the maximum expansion ratio and rate of collapse of foams. Higher water contents were associated with higher expansion ratios but also faster rates of collapse. The two foaming devices used in this study produced foams with similar properties. Rheological tests conducted on foamed binder residues revealed that the foaming process slightly increased the high temperature continuous performance grade (PG) of the binder. [ABSTRACT FROM AUTHOR]

Techniques for making epoxy-coated reinforcement more corrosion resistant, including epoxies with increased adhesion to the steel; concrete with a decreased water cement ratio; concrete containing calcium nitrite or one of two organic corrosion inhibitors; bars with a primer coating containing microencapsulated calcium nitrite applied prior to epoxy application; and bars coated with zinc prior to epoxy application are compared based on the chloride content required to initiate corrosion and corrosion losses using the southern exposure and cracked beam tests. The coatings on all bars are penetrated prior to testing to simulate damage in the field. The results indicate that, even when damaged, conventional epoxy coatings result in much higher concrete chloride contents at corrosion initiation and much lower corrosion losses than exhibited by conventional reinforcement. A reduced water-cement ratio, corrosion inhibitors, and the primer coating containing microencapsulated calcium nitrite provide protection in uncracked but less or no protection in cracked concrete. The bars coated with zinc prior to epoxy application exhibit relatively high corrosion rates because of preferential losses to the zinc, and no improvement in corrosion performance is observed for epoxies with increased adhesion. [ABSTRACT FROM AUTHOR]

The paper presents vertical pressure values occurring under the center line of uniformly loaded laboratory model tests of a surface strip footing on a sand bed. The vertical pressure distribution in medium dense sand was measured using miniature pressure sensors. The experimental measures obtained from the model test program have been compared with values obtained from earlier theories. Tests were performed in plane strain conditions. Finally, the results obtained from experiments and theoretically obtained values were discussed. The results indicated that the distribution of pressure was not the same for every load level. It was found that the pressure distributions fit Westergaard distribution better at lower loads. They approach the pressure predicted by an earlier study as the applied loads reach bearing capacity values. [ABSTRACT FROM AUTHOR]