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Passive earth pressure is recorded in two different tests, using a 6.7-m long, 2.9-m wide soil container. In these tests, sand with 7% silt content is densely compacted behind a moveable test wall to a supported height of 1.68 m (5.5 ft). Lateral load is applied to the vertical reinforced concrete wall section, which displaces freely along with the adjacent backfill in the horizontal and vertical directions. The recorded passive resistance is found to increase until a peak is reached at a horizontal displacement of 2.7-3% of the supported backfill height, decreasing thereafter to a residual level. In this test configuration, a triangular failure wedge shape is observed, due to the low mobilized wall-soil friction. Backfill strength parameters are estimated based on this observed failure mechanism. From these estimates, along with triaxial and direct shear test data, theoretical predictions are compared with the measured passive resistance. Using the test data, a calibrated finite-element model is employed to produce additional load-displacement curves for a wider range of practical applications (e.g., potential bridge deck displacement during a strong earthquake). Hyperbolic model approximations of the load-displacement curves are also provided. DOI: 10.1061/(ASCE)GT.1943-5606.0000386 CE Database subject headings: Passive pressure; Earth pressure; Retaining walls; Full-scale tests; Soil-structure interactions; Load factors; Simulation; Displacement. Author keywords: Passive pressure; Retaining wall: Large-scale tests; Soil-structure interaction.

The statistics of pressure fluctuations above and within three types of porous granular beds such as in gravel bed streams, rivers, and man-made canals are investigated by data gained via laboratory flume experiments. The flow conditions examined include a diversity of hydrodynamic loads that increase up to the point where single grains are moving from time to time, without causing severe modification to the bed texture and the related positions of the pressure sensors. Analysis is performed by means of histograms and spectral techniques and vertical intensity profiles. Two simplified equations are found that describe the vertical decrease for the standard deviation of the measured fluctuations indicating drag and lift, respectively, nondimensionalized by the mean bed shear stress. The former fluctuation is described by a crude linear fit, whereas the latter clearly shows that the lift intensity decreases exponentially in the porous bed with a decay distance of one to two times the equivalent grain roughness. Within the subsurface layer the standard deviation reaches a nonzero constant, mainly dominated by long-wave pressure fields that are convected in the outer flow. These findings can be used in future sediment transport models that use force balance approaches to determine incipient motion conditions. DOI: 10.1061/(ASCE)HY.1943-7900.0000251 CE Database subject headings: Open channel flow; Gravel; Turbulence; Power spectral density; Laboratory tests; River beds. Author keywords: Open-channel flow; Gravel bed; Turbulence; Pressure fluctuation; Spectral density; Interstitial.

The hydrant pressure head in an on-demand water distribution system can be subject to high fluctuation depending on the discharge flowing inside the pipes, with consequent impacts on the performance of on-farm irrigation systems. In this work, an Italian water distribution system was analyzed using the AKLA model at upstream discharges of 1,200 and 600 L x [s.sup.-1] to estimate the range of hydrant pressure variation. A computer model was developed, calibrated, and used to evaluate the performance of a drip irrigation system by relating the on-farm network with the hydrant characteristic curve at a certain operating status. The flow regulator within the hydrant played an important role in stabilizing the performance of the network at hydrant pressures higher than 27 m. At lower hydrant pressures, to apply the same amount of water, irrigation time must be extended by 17 and 95% for pressure heads of 20 and 12 m, respectively. These approaches described have great utility to ensure adequate irrigation management when water is delivered by pressurized on-demand systems. DOI: 10.1061/(ASCE)IR.1943-4774.0000170 CE Database subject headings: Network analysis; Hydraulic networks; Hydraulic pressure; Trickle irrigation; Water flow; Water distribution systems. Author keywords: Network characteristic curve; Hydrant pressure variation; Irrigation performance; Network analysis; Flow regulator.

This paper presents new results for numerical predictions of air flow and pressure distribution in two commonly used elbows: (1) 90[degrees] mitered duct elbows with turning vanes having 0.05 m radius, 0.038 m vane spacing and (2) 90[degrees] mitered duct elbows without turning vanes, in 0.2 x 0.2 m (8 in. X 8 in.) duct cross section using the STAR-CD computational fluid dynamics (CFD) code. A k-[epsilon] turbulence model for high Reynolds number and k-[epsilon] Chen model were used for that purpose for comparative purposes. The simulation used 13 different Reynolds numbers chosen between the range of 1 X [10.sup.5] and 2 x [10.sup.6]. To validate the CFD results, the results of two experimental papers using guided vanes were compared with simulated vane runs under the same condition. The first experimental study used a 0.6 x 0.6 m (24 in. X 24 in.) square elbow with 0.05 m radius, 0.038 m vane spacing and air velocities at 2.54 m/s (500 fpm) and 25.4 m/s (5,000 fpm), the second experiment used a 0.81 X 0.2 m (32 in. X 8 in.) rectangular elbow geometry with 0.05 m radius, 0.038 m vane spacing with air velocities from 10.16 m/s (2,000 fpm) to 13.97 m/s (2,750 fpm). For Reynolds numbers (1.00-2.00) x [10.sup.5] the pressure drop difference between vaned and unvaned elbows was found to be 35 Pa as compared to 145 Pa. The simulations also agreed reasonably well with published experimental results. For the 0.6X0.6 m (24 in. x 24 in.) square elbow and 0.81 X 0.2 m (32 in. X 8 in.) rectangular elbow with vanes, the difference in pressure drop was 3.9 and 4.1% respectively and indicates that CFD models can be used for predictive purposes in this important HVAC applications area. DOI: 10.1061/(ASCE)0733-9402(2009)135:4(119) CE Database subject headings: Flow simulation; Velocity profile; Predictions; Air flow.

A real-time estimation of water distribution system state variables such as nodal pressures and chlorine concentrations can lead to savings in time and money and provide better customer service. While a good knowledge of nodal demands is prerequisite for pressure and water quality prediction, little effort has been placed in real-time demand estimation. This study presents a real-time demand estimation method using field measurement provided by supervisory control and data acquisition systems. For real-time demand estimation, a recursive state estimator based on weighted least-squares scheme and Kalman filter are applied. Furthermore, based on estimated demands, real-time nodal pressures and chlorine concentrations are predicted. The uncertainties in demand estimates and predicted state variables are quantified in terms of confidence limits. The approximate methods such as first-order second-moment analysis and Latin hypercube sampling are used for uncertainty quantification and verified by Monte Carlo simulation. Application to a real network with synthetically generated data gives good demand estimations and reliable predictions of nodal pressure and chlorine concentration. Alternative measurement data sets are compared to assess the value of measurement types for demand estimation. With the defined measurement error magnitudes, pipe flow data are significantly more important than pressure head measurements in estimating demands with a high degree of confidence. DOI: 10.1061/(ASCE)HY.1943-7900.0000086 CE Database subject headings: Estimation; Least squares method; Water distribution systems; Uncertainty principles; Limit analysis.

The performance of rigid surface structures such as concrete pavements and slabs-on-grade supported by a deteriorated subgrade and experiencing local contact loss is investigated experimentally and numerically in this study. A laboratory setup has been designed to facilitate the simulation of subsurface erosion and measure the changes in contact pressure at selected locations under a slab-on-grade supported on granular material. The presence of erosion voids under a slab-on-grade can lead to rapid increase in the contact pressure in the immediate vicinity of the void in addition to an increase in tensile stresses at the outermost fibers of the slab. This preliminary study suggests that efforts to detect and arrest the growth of erosion voids under slabs-on-grade should be made before the voids reach the size where significant loss of support develops and the tensile strength of the slab material is exceeded. DOI: 10.1061/(ASCE)GT.1943-5606.0000097 CE Database subject headings: Slabs; Soil erosion; Deterioration; Voids; Subgrades; Underground structures.

This paper presents the practical elastic settlement formulae for the eccentrically loaded surface footings resting upon an elastic mass. The presented closed-form solutions can be readily implemented into the practice allowing efficient and accurate prediction of elastic settlement under the rectangular footing which is subjected to the biaxial bending. The presented solutions are determined by evaluating the integration of strain expressions based on the Boussinesq stress equations. The common assumption of linear contact pressure in footing-soil interface is adopted for the solutions. The presented formulae are validated to be used for the settlement under any point of linear full-contact loading and their applicability to the current design process is demonstrated. The solutions are also developed for the theoretical cases where the location of incompressible soil layer is infinitely deep. The simplified influence factors are presented graphically and the numerical examples are provided for their practical use. In this respect, the paper represents a significant step forward in understanding of elastic settlement, rotation, and differential elastic settlement under eccentrically loaded footings. DOI: 10.1061/(ASCE)GT.1943-5606.0000113 CE Database subject headings: Settlement; Sand; Contact pressure; Footings; Eccentric loads.

A series of centrifuge model tests was conducted to investigate the behavior of pile groups of various sizes and configurations behind a retaining wall in very soft clay. With a 1.2-m excavation in front of the wall, which may simulate the initial stage of an excavation prior to strutting, the test results reveal that the induced bending moment on an individual pile in a free-head pile group is always smaller than that on a corresponding single pile located at the same distance behind the wall. This is attributed to the shadowing and reinforcing effects of other piles within the group. The degree of shadowing experienced by a pile depends on its relative position in the pile group. With a capped-head pile group, the individual piles are forced to interact in unison though subjected to different magnitudes of soil movement. Thus, despite being subjected to a larger soil movement, the induced bending moment on the front piles is moderated by the rear piles through the pile cap. A finite element program developed at the National University of Singapore is employed to back-analyze the centrifuge test data. The program gives a reasonably good prediction of the induced pile bending moments provided an appropriate modification factor is applied for the free-field soil movement and the amount of restraint provided by the pile cap is properly accounted for. The modification factor applied to the free-field soil movement accounts the reinforcing effect of the piles on the soil movement. DOI: 10.1061/(ASCE)GT.1943-5606.0000095 CE Database subject headings: Pile groups; Bending; Centrifuge models; Clays; Deflection; Excavation; Retaining walls; Soil pressure.

This technical note describes the derivation of an analytical expression for the total active force on the retaining wall for c-[phi] soil backfill considering both the horizontal and vertical seismic coefficients. The results based on this expression are compared with those obtained from earlier analytical expressions for the active force for c-[phi] soil backfill under seismic conditions, and found to have a similar trend of variation. The parametric study shows that the inclination of the critical failure plane with the horizontal plane decreases with the increase in values of seismic coefficients; the decrease being more for their higher values. The total active force increases with the increase in value of horizontal seismic coefficient; while it decreases with the increase in value of vertical seismic coefficient except for a very high value of horizontal seismic coefficient. Design charts are presented for various combinations of horizontal and vertical seismic coefficients ([k.sub.h] and [k.sub.v]), and values of cohesion and angle of shearing resistance for estimating the total active force on the retaining wall for c-[phi] soil backfill for practical applications. DOI: 10.1061/(ASCE)GT.1943-5606.0000003 CE Database subject headings: Backfills; Earth pressure; Earthquakes; Retaining walls; Seismic loads.

The present work is a numerical investigation on waves generated by a pressure disturbance moving at constant speed in a channel with a variable cross-channel depth profile. The channel profile, which is uniform in the along-channel direction, has a deep trench located along the centerline of the channel, and shallow banks near the channel walls. Characteristic features upstream and downstream of the moving pressure disturbance are related to the parameters of the pressure disturbance and the cross-channel profile. Our numerical investigation is based on the COULWAVE long wave model. DOI: 10.1061/(ASCE)0733-950X(2009) 135:3(120) CE Database subject headings: Long waves; Solitary waves; Wave propagation; Shallow water; Channel flow; Topography; Cross sections; Pressure distribution.

Cyclic loading has been known to induce fluid flow and thus mechanotransduction in bones. In the past, four-point bending tests have been used exclusively in studying fluid flow in bones. In order to better understand the mechanism of deformation and fluid flow under loading, compression tests were done on trabecular bone specimens under drained and undrained conditions. In the drained tests, the volume change was observed, whereas in the undrained tests, excess pore fluid pressure was measured. Cyclic loading tests were conducted in addition to monotonic loading tests to observe the permanent volume change or excess pore fluid pressure with loading cycles. A fast loading rate gave a sharp rise in the excess fluid pressure compared to a slow loading rate. The strength and stiffness of the specimens appeared to deteriorate with an increased speed of loadings, but there was no appreciable difference between the results obtained from drained and undrained tests. The drained and undrained tests as described allowed a better understanding of bone behavior under loadings for a coupled stress-flow analysis. DOI: 10.1061/(ASCE)0733-9399(2009) 135:5(375) CE Database subject headings: Human factors; Biological properties; Mechanical properties; Deformation; Cyclic loads.

We here extend the theory of microporomechanics by Dormieux et al. to multiple pore spaces. As an application, we reveal, on the basis of a recently validated multiscale elastic model for bone tissues by Fritsch and Hellmich, the effects of multiple pore pressures in various, scale-separated pore spaces, on the overall behavior of the multiporous composite material. Thereby, our focus is on the lacunar pore space, and on its interplay with the pore spaces found further below: not only those between the mineral crystals (of some 10 nm characteristic pore size) but also those of the collagen molecules building up (micro-)fibrils (with a little more than 1 nm distance between these molecules). Our results clearly show that the interplay between pore pressure and skeleton deformation depends strongly on the loading direction and on the characteristic size of the pores--hence, we can conclude that the consideration of these strongly hierarchical and anisotropic effects in whole-organ simulations including fluid mass transport, would allow for valuable new insights into the ongoing discussion on poromechanobiology of bone. DOI: 10.1061/(ASCE)EM. 1943-7889.0000001 CE Database subject headings: Pore pressures; Elasticity; Foundations; Drainage; Material properties.

Recently, several studies on the dissipation of excess pore pressure in liquefied sandy grounds have been reported on evaluation of postliquefaction behavior of structures. To further contribute to the understanding of this complicated dynamic phenomenon, centrifuge tests were performed in this research to analyze the liquefaction behavior of level saturated sandy grounds. The test results showed that the excess pore pressure in the liquefied sand was dissipated by the combined process of the solidification of the sand grains and the consolidation of the solidified layer. Based on the test results, a nonlinear model for the solidified layer thickness versus time, i.e., the solidification velocity, was developed. A new dissipation model was also developed by combining the nonlinear solidification model with Scott's theory to improve the prediction for the time history of excess pore pressure. In addition, a method for evaluating the input parameters in the dissipation model was proposed by relating the parameters to the particle size and the relative density of soils. The proposed dissipation model properly estimated the dissipation of excess pore pressure with time observed in the centrifuge experiments. CE Database subject headings: Soil liquefaction; Soil consolidation; Solidification; Centrifuge models; Sand.

Bridge abutments typically contain a backwall element that is designed to break free of its base support when struck by a bridge deck during an earthquake event and push into the abutment backfill soils. Results are presented for a full-scale cyclic lateral load test of an abutment backwall configured to represent the dimensions (1.7 m height), boundary conditions, and backfill materials (compacted silty sand) that are typical of California bridge design practice. An innovative loading system was utilized that operates under displacement control and that assures horizontal wall displacement with minimal vertical displacement. The applied horizontal displacement ranged from null to approximately 11% of the wall height (0.11H). The maximum earth pressure occurred at a wall displacement of 0.03H and corresponded to a passive earth pressure coefficient of [K.sub.p]= 16.3. The measured force distribution applied to the wall from hydraulic actuators allowed the soil pressure distribution to be inferred as triangular in shape and the mobilized wall-soil interface friction to be evaluated as approximately one-third to one-half of the soil friction angle. Post-test trenching of the backfill showed a log-spiral principal failure surface at depth with several relatively minor shear surfaces further up in the passive wedge. The ultimate passive resistance is well estimated by the log-spiral method and a method of slices approach. The shape of the load-deflection relationship is well estimated by models that produce a hyperbolic curve shape. CE Database subject headings: Bridge abutments; Passive pressure; Seismic design; Lateral pressure; Backfills; Granular materials.

This paper describes the development of analytical models used to predict the response of bonded membrane retrofit concrete masonry walls subjected to out-of-plane impulse pressure loads. Full scale tests have shown significant improvement in the resistance of unreinforced concrete masonry walls retrofitted by membrane materials. The majority of the membrane retrofit concrete masonry wails survived compared to their unretrofitted counterparts that collapsed. Polymer membrane retrofit materials may be sprayed on, trowled on, or attached with adhesives to the tension face of the wall. Other membrane materials such as thin steel or aluminum sheets may be attached to the tension face of the wall using expansion screws or other structurally sound methods. Resistance functions previously presented by the writers for membrane retrofit concrete masonry walls are used in the development of the response. Single-degree-of-freedom equations are developed to predict the response of these walls to impulse pressure and the results of the analysis are compared with available full-scale tests. CE Database subject headings: Dynamic pressure; Membranes; Rehabilitation; Masonry; Walls; Concrete; Polymers.

This technical paper presents analytical expressions to estimate the probability function of head losses in any path of an on-demand branched irrigation network. They are developed for estimating the probability of pressure deficit of a given magnitude at any hydrant. They are also useful for examining the probability of a power deficit at a pumping station designed to guarantee service to a hydrant, as well as the head characteristic curve of the distribution system linked to a definite probability. All this quantified information is useful for decision making on network design and performance. The probabilities calculated with the developed expressions can be taken as complementary or alternative concepts to C1ement's classical design flow method, which is taken here as a benchmark for comparisons. Illustrative examples of network designs are presented to validate the proposed expressions. The least cost design solutions using C1ement's design flows are compared with design solutions here obtained to get the same probability of pressure deficit at the most unfavorable hydrants. The new solutions are less expensive because the flow constraint can be avoided. CE Database subject headings: Network analysis; Pipeline design; Pressure distribution; Probability distribution; Simulation models; Statistics; Water pipelines.

A finite strain micromorphic pressure-sensitive plasticity model is formulated starting with thermodynamically conjugate stresses and plastic deformation rates in the reduced dissipation inequality, written in the intermediate configuration. Isotropic linear elasticity and nonassociative Drucker--Prager plasticity with cohesion hardening/softening are assumed for the constitutive equations. The reduced dissipation inequality dictates three levels of plastic evolution: (1) evolution of [F.sup.p], the plastic part of the deformation gradient; (2) evolution of [[chi].sup.p], the plastic part of the microdeformation tensor; and (3) evolution of [bar.[nabla]][[chi].sup.p], the covariant derivative of [[chi].sup.p]. A semi-implicit time integration of the stress and plastic evolution equations is outlined after assuming small elastic deformations and Cartesian coordinates for the current configuration. CE Database subject headings: Plasticity; Strain; Pressure; Thermodynamics; Microstructure.

It has been recognized that the ductility demands on a superstructure might be reduced by allowing rocking behavior and mobilization of the ultimate capacity of shallow foundations during seismic loading. However, the absence of practical reliable foundation modeling techniques to accurately design foundations with the desired capacity and energy dissipation characteristics and concerns about permanent deformations have hindered the use of nonlinear soil-foundation-structure interaction as a designed mechanism for improving performance of structural systems. This paper presents a new 'contact interface model' that has been developed to provide nonlinear relations between cyclic loads and displacements of the footing-soil system during combined cyclic loading (vertical, shear, and moment). The rigid footing and the soil beneath the footing in the zone of influence, considered as a macroelement, ate modeled by keeping track of the geometry of the soil surface beneath the footing, along with the kinematics of the footing-soil system, interaction diagrams in vertical, shear, and moment space, and the introduction of a parameter, critical contact area ratio (A/[A.sub.c]); the ratio of footing area (A) to the footing contact area required to support vertical and shear loads ([A.sub.c]). Several contact interface model simulations were carried out and the model simulations are compared with centrifuge model test results. Using only six user-defined model input parameters, the contact interface model is capable of capturing the essential features (load capacities, stiffness degradation, energy dissipation, and deformations) of shallow foundations subjected to combined cyclic loading. CE Database subject headings: Shallow foundations; Ductility; Cyclic loads; Combined loads; Contact pressure.

The context of structural monitoring of concrete dams as part of hydropower assets management is described. A tool that fits well into this context is the control of the uplift pressure of concrete dams. A monitoring technique suitable for this purpose was developed based on an automated water-level measurement technique using time-domain reflectometry and standard air-dielectric coaxial cable sensors. The signal is interpreted automatically by applying a threshold method to determine the apparent water level, which is then used to calculate the uplift pressure. A field test at a concrete dam column displayed consistent results, which were used as input to a reliability-based stability safety analysis. The results show that this technique can be very useful for uplift pressure monitoring. The information determined can serve as input to the maintenance work as well as assist engineering decisions. CE Database subject headings: Dams, concrete; Uplift pressure; Structural reliability; Monitoring.

Between 2001 and 2002, a 6.4-m (21.0-ft) diameter corrugated steel pipe culvert was erected and buried under a 22.9-m (75.0-ft) highway embankment fill in Meigs County, Ohio. This steel pipe culvert was the first of its kind to be constructed in the southeastern region of Ohio. The culvert structure was selected by the Ohio Department of Transportation over an alternative of a 5 million conventional bridge structure, because it would cost about $3.4 million less. The field performance of the culvert was monitored by measuring the pressure distribution around the pipe, as well as the deflections of the pipe culvert during and after construction. The culvert study also included comparing measured field performance with numerical predictions given by the finite-element computer program CANDE-89. CANDE-89 with the slotted joint option had a limited ability to simulate the actual field behavior of the large-diameter multiplate culvert structure, especially in the earlier stages of construction. CE Database subject headings: Culverts; Steel pipes; Deflection; Soil pressure; Simulation; Computer analysis; Ohio; Measurement.

Soil nailing has been widely used in many places in the world in the last two decades because of its technical and economical advantages. The nail--soil interface shear strength is an important parameter in soil nail design. This parameter is governed by a number of factors, among which the influence of the overburden pressure (or soil depth) is the most controversial. There are differing views concerning the effect of overburden on the nail--soil interface shear strength. In order to examine the influence of the overburden pressure, a series of laboratory pullout tests on soil nails installed in compacted completely decomposed granite fill have been conducted using two pullout boxes. Numerical simulations have also been carried out and the results are compared with the pullout test data. The procedures of the pullout tests and new features of the pullout boxes used are briefly described. Changes of the vertical stress in soil close to the nail throughout the course of soil nail installation and pullout are presented and discussed in detail. It is observed from the results of this study that the installation process of soil nail induced significant vertical stress changes in soil around the soil nails, and that the soil nail pullout shear resistance is independent of the overburden pressure (or soil depth). CE Database subject headings: Soil nailing; Shear resistance; Fills; Soil compaction; Shear strength; Soil pressure.

Experimental studies on the hydraulics of flow through and over gabion-stepped weirs are presented. Two flow components were observed, i.e., base flow through the void between filled stones and overflow on the gabions. The energy loss ratios in the gabion-stepped weirs are greater than those in the corresponding horizontal stepped weirs by approximately 7, 10, and 14% for weir slopes of 30, 45, and 60[degrees], respectively. As a result, the velocity at the outlet is lower. Stone size and shape have little influence on the energy loss and flow velocity as compared to the increasing effect of the weir slope. The pressure acting on the step face for the gabion-stepped weirs is less than that of the horizontal steps owing to the cushioning effect generated by filled stones. To reduce pressure on a step face at a fixed discharge for different weir slopes, the void ratio of the filled stones should be low to allow a small amount of base flow. The pressure distribution pattern on the horizontal face of a step is provided. DOI: 10.1061/(ASCE)0733-9429(2008) 134:8(1147) CE Database subject headings: Weirs; Hydraulic structures; Overflow; Energy; Pressure measurement.

The paper presents the methodologies and results of an experimental study aimed at measuring the soil contact pressures which develop on a buried structure as it interacts with the surrounding soil under load. The study has been based on measurements made on model structures tested in a pressure chamber filled with a fine uniform sand. The buried model structure was a very rigid right cylinder designed such that it could be fitted with roofs of different thicknesses. The structure bottom and roof were instrumented with newly designed and constructed soil pressure cells based on the null response concept. The device is unaffected by the issues that affect the use of traditional soil pressure cells. The development of pressure on the structure was measured as uniform pressure was applied to the soil surface. The results illustrate the effect of roof stiffness on the development of pressure at the roof center. The midroof pressure was seen to increase with roof stiffness, however the development of pressure was also seen to be dependent upon the actual deflection. In the case of a flexible roof it was seen that the development of contact pressure is a nonlinear function of the pressure applied at the soil surface and is highly dependent upon stress history. In contrast, it was seen that pressure on a stiff roof develops as a linear function of pressure applied at the soil surface and is less dependent of stress history. The results of the model tests together with soil stiffness data supplied in the paper will be useful in the calibration and validation of numerical and analytical frameworks. CE Database subject headings: Soil pressure; Measurement; Underground structures; Validation.

The analysis of the dynamic response of a pressurized water pipeline system is important for the design and also the integrity monitoring of these systems. An efficient method for summarizing the behavior of a pipeline system is through the determination of their system response functions. These functions can be extracted by injecting a pressure signal with a wide bandwidth that persists over the length of a pipeline system. Unlike electrical and mechanical systems, generating such signals in pressurized water systems is difficult. Valves capable of generating a signal against the system back-pressure often lack the necessary maneuverability to ensure the signal is sharp (and hence with high-frequency content) and the generated transient is often large in amplitude, risking damage to the system. A method for generating a small amplitude transient signal with a wide band of frequencies is desirable. This paper presents the design for a side discharge valve for generating a pseudorandom binary sequence of pressure changes that are of a small magnitude in relation to the steady state head of the pipeline. The pseudorandom pressure sequence is used to provide an estimate of the system response function. The continuous form of the signal allows the amplitude of each individual pulse within the signal to be small while maintaining the same signal bandwidth. The valve has been tested experimentally and was found to provide a good match with the theoretical response of the pipeline. The method provides a practical alternative to frequency sweeping using sinusoidal signals or sharp valve closures for the extraction of the response functions. Once determined, the system response function can be utilized to detect system faults such as leaks and blockages. DOI: 10.1061/(ASCE)0733-9429(2008)134:6(858) CE Database subject headings: Pipes; Pressure measurement; Transfer functions; Transient flow; Water pipelines.

To study the performance of sheet pile wall in peat during roadway construction, a long-term instrumentation program was conducted over a period of two years, measuring total lateral earth pressures, sheet pile deflections, soil movements, and water table level variances during construction. The analysis of field data indicated: (1) The earth pressure distribution in peat matched well with the classic Rankine earth pressure; (2) the expected long-term postconstruction sheet pile movement due to the creep behavior of peat was not observed; (3) fully passive earth pressure in peat was mobilized once the maximum measured sheet pile deflection exceeded 0.8% of sheet pile length; and (4) arching effect due to the protruding cross section of sheet pile caused pressure differences of 3- 10 kPa between the inside web and outside web of the sheeting. Then, all the construction stages were continuously modeled by finite- element method and the calculated results were compared with the field measurements. The comparisons showed that the calculated results were consistent with the field data and provided reasonable explanations and helpful insights to understand soil--structure interaction mechanism. Finally, some conclusions and suggestions for sheet pile design and construction in peat were reached. CE Database subject headings: Earth pressure; Sheet pile; Instrumentation; Finite element method; Retaining walls; Waterfront structures.

This paper presents experimental data on the variation of lateral earth pressure against a nonyielding retaining wall due to soil filling and vibratory compaction. Air-dry Ottawa sand was placed in five lifts and each lift was compacted to achieve a relative density of 75%. Each compacted lift was 0.3 m thick. The instrumented nonyielding wall facility at National Chiao Tung University in Taiwan was used to investigate the effects of vibratory compaction on the change of stresses at the soil-wall interface. Based on the experimental data it has been found that, for a compacted backfill, the vertical overburden pressure can also be properly estimated with the traditional equation [[sigma].sub.v] = [gamma]z. The effects of vibratory compaction on the vertical pressure in the backfill were insignificant. On the vertical nonyielding wall, extra horizontal earth pressure was induced by vibratory compaction. After compaction, the lateral earth pressure measured near the top of the wall was almost identical to the passive Rankine pressure. It is concluded that as the cyclic compacting stress applied on the surface of the backfill exceeded the ultimate bearing capacity of the foundation soil, a shear failure zone would develop in the uppermost layer of the backfill. For a soil element under lateral compression, the vertical overburden pressure remained unchanged, and the horizontal stress increased to the Rankine passive pressure. It was also found that the compaction-influenced zone rose with the rising compaction surface. The horizontal earth pressure measured below the compaction-influenced zone converged to the Jaky state of stress. CE Database subject headings: Soil compaction; Earth pressure; Model tests; Retaining walls; Sand.

Earth pressure theories occupy a paramount position in the field of geotechnical engineering. An experimental investigation of the at-rest earth pressure of overconsolidated cohesionless soil acting on retaining walls was conducted. A prototype model of a vertical rough wall, retaining horizontal backfill, was developed in the laboratory. The model was instrumented to measure the earth pressure at selected points on the wall, the total earth force acting on the wall, and the overconsolidation ratio (OCR) in the sand mass. Tests were conducted on walls retaining homogeneous overconsolidated dense, medium, or loose sands. Test results showed that the coefficient of at-rest earth pressure increases with the increase of the OCR. The present experimental results were used to examine the empirical formulas available in the literature. It can be reported that these formulas compared well with the experimental results for OCR values up to 3. An empirical formula is proposed to predict the coefficient of at-rest earth pressure for overconsolidated cohesionless soils. The results obtained by this formula agreed well with the present experimental results for all values of overconsolidation ratios. DOI: 10.1061/(ASCE)1090-0241(2008)134:3(408) CE Database subject headings: Overconsolidated soils; Cohesionless soils; Geotechnical engineering.

Nonlinear shear modulas degradation characteristics are of interest in many geotechnical engineering applications, such as ground deformation caused by seismic shaking and deep excavations in clay, weathered rock, and stabilized soil. This paper presents an approach to derive the secant shear modulus degradation characteristics from in sita pressuremeter tests, which is based on a digital filter algorithm. The algorithm is described, and data preparation procedures are presented. Use of the algorithm is illustrated by means of pressuremeter data for soils stabilized with deep mixing methods on the Boston central artery/tunnel (CA/T). The nonlinear secant shear modulas degradation characteristics from the digital filter approach are shown to be in good agreement with those from the curve fitting and transformed-strain approaches. They also compare favorably with the results of other in sita and laboratory tests performed in conjunction with the CA/T stabilized soils. The algorithm is implemented by a 26-1ine MATLAB code in an appendix of the paper. CE Database subject headings: Soil mixing; Filters; In sita tests; Pressuremeters; Shear modulas; Soil cement; Degradation.

Using a depth-averaged model to obtain the velocity and pressure distributions in the vertical direction is difficult. A multiplayer model is an option that can be used to improve on the depth-averaged model. However, the unknown flow depth needs to be predicted first and then divided into layers as an input for the multilayer model. An improved multilayer model is proposed here by introducing an implicit layer dividing interfaces that are associated with the flow velocity and pressure distribution. The formulation of interfaces also applies to boundary faces: Free surface and channel beds. Therefore, each flow layer behaves like that in the classical depth-averaged model. Subsequently the governing equations are also simplified due to the vanishing terms related to interfacial flow exchanges. This improved model has been satisfactorily applied to steady flow simulations in three cases: Flow over a slope transition from mild to steep, from steep to mild, and over a trapezoidal weir. The results demonstrate the efficiency and validity of the proposed models to simulate open channel flows with bed slope changes. CE Database subject headings: Velocity; Steady flow; Slopes; Open channel flow; Pressure.

The potential for hydraulic transients in the West Area Combined Sewer Overflow Tunnel System of the City of Atlanta was investigated by numerical modeling. Different design alternatives were evaluated to mitigate pressure oscillations, backflows, and flooding during storm events. A dynamic transient model was developed to simulate the transition from gravity flow to pressurized flow that would occur during a storm event. The model is able to simulate pressurization with pipe-filling bore or gradual-flow regime transition. Numerical results compare well with experimental data on single pipe flows. Following a brief description of the model, the paper discusses the pressure transients simulated during the filling of the tunnels for both the original and improved designs. CE Database subject headings: Hydraulic transients; Numerical models; Drainage; Case reports; Georgia; Combined sewer overflow; Tunnels; Pressure; Municipal wastes.

An elastoplastic pressuremeter theory for cohesive soil has been used in the design of construction, such as retaining walls, slope stability, or foundation engineering. This theory takes into account the plasticity along the vertical and horizontal planes and allows for the determination of the conventional limit pressure. We compute here the conventional limit pressure using the Plaxis program to check the validity of the theoretical results. First, we present the theory used for the interpretation of the pressuremeter test in cohesive soil and its extension to the conventional limit pressure, which is defined as the pressure at the borehole wall for a volume increase AV equal to the initial volume of the borehole. One of the main results is the theoretical expression of the conventional limit pressure. This volume variation is linked to a radial strain of [square root of (2)]-1. This conventional limit pressure can be directly measured with the pressuremeter, whereas the theoretical limit pressure is expressed as an infinite expansion and cannot be directly measured. Then, we validate this theory by using finite elements, and determine the conventional limit pressure with the Tresca standard model of Plaxis, which is compared to the theoretical expression. Conclusions are drawn on the validity of this new theory which allows the measurement and the control of the shearing modulus and shear strength of the natural soil. CE Database subject headings: Pressuremeters; Elasticity; Plasticity; Shear strength; Validation; Cohesive soils.

This paper presents a mathematical model for the pressure inside the vapor space of an underground storage tank (UST). Using mass balances based on dispensing activities, vapor recovery, evaporation, leaks, and the safety vent, the model resulted in a system of nonlinear differential equations with unknown parameters, leak rate and evaporation rate. Given the leak rate and evaporation rate, the pressure inside the UST can be obtained by solving the system of differential equations numerically. Given the pressure inside a UST over a period of time, one can find the evaporation and leak rates such that the calculated pressure from our model best fits the given pressure data. This optimal value of leak rate can allow us to determine whether the UST system is leaking and if the leak rate is above the EPA standard. Numerical results and statistical analysis of our model are also presented. CE Database subject headings: Air pollution; Emissions: Leakage; Underground storage; Gas recovery; Storage tanks.

Breakwaters often stand on a rubble mound or have a rubble berm in front of the structure. The pressure-impulse model for violent water-wave impact on a wall fronted by an impermeable bed is extended to include a porous region simulating a porous berm. The effect of different berm porosities on the pressure impulse is investigated. Even some large changes in porosity are found to have little effect (at most 20%) on the pressure impulse both on the wall and along the berm. However, in this study evolution toward the wall is not included.

Often when a plunging breaker impacts on a wall, an air pocket is trapped at the wall. This paper extends a pressure-impulse model for wave impact on a wall to include a simple model of a trapped air pocket. The inclusion of an air pocket leads to a higher impulse at impact for a given wave as there is some rebound of the water. The model is shown to compare satisfactorily with small-scale experimental data performed on a caisson breakwater with an impermeable berm. The effect of a porous berm on pressure impulse is investigated theoretically in a companion paper.

Comparison of predicted with observed attenuation of pressure fluctuations shows that wave heights can be estimated with observations from a pressure sensor that is buried a known depth in fine sand. The attenuation of pressure fluctuations within the sand bed under unbroken shoaling waves, bores in the surf zone, and swash near the shoreline was measured with vertical stacks of buried pressure sensors. The attenuation increased with increasing frequency and depth below the bed surface, consistent with previous observations under nonbreaking waves in deeper water and with model predictions based on poro-elastic theory. In the limit of an infinitely deep soil skeleton that is much more compressible than the pore fluid, the predicted pressure fluctuations decrease exponentially with increasing burial depth, and the attenuation is independent of the sediment properties. For the fine-grained sand beds considered here, this exponential limit accurately predicts the observed attenuation.

The dynamic characteristics of fluctuating pressure measuring systems composed of connection tubing and pressure transducers were analyzed. A method of correction for the effects of resonance and viscous damping on the measured pressure fluctuations was proposed. A mathematical model of the measuring system was formed combining the governing equations of the unsteady flow in the rigid connection tubing and the corresponding volumetric deformation in the transducer. Numerical solution of the governing equations were described. The phase shift between the velocity amplitude on the tube axis and the maximum wall shear stress was obtained from numerical solutions for a wide frequency range of sinusoidal pressure variations. Amplification and attenuation of sinusoidal pressure variations were given in terms of dimensionless parameters. An in situ dynamic calibration to obtain lumped compliance of the measuring system was described. The method was applied to correct the measured pressure fluctuations obtained from different sources. The mathematical and numerical model was successful in correcting amplification and attenuation occurring on different frequency bands of the same pressure record with random fluctuations.

The design parameters in sands were determined using the cone pressuremeter. Results were interpreted by employing a theory that incorporates the major aspects of sand behavior around an expanding cavity. Results show that the cone pressuremeter and the theory may be effectively applied for friction angle and initial state parameter estimation. Additional efforts, however, should be conducted to ensure that test data differences are caused by soil behavior and not test procedures and equipment properties.

A series of dilatometer test profiles were carried out in a calibration chamber on Toyoura sand using a standard blade and a special research dilatometer. Pluviated sand samples were prepared using various combinations of boundary conditions, relative density, and stress history. The research dilatometer probe consists of a standard blade modified internally to allow monitoring of the complete pressure-displacement soil response during a test. Precise performance of small unload-reload cycles can also be performed to evaluate elastic deformation properties. The pressure-displacement response during the expansion tests clearly shows the influence of stress history and density. The stiffness of the Toyoura sand from both dilatometers were also compared to that measured in laboratory monotonic shear tests and to various empirical relationships. The results suggest that the moduli measured from the unload-reload cycles during the research dilatometer tests reflect the elastic properties of the soil and can be correlated to results from resonant column tests and monotonic torsional shear tests. Modulus values measured with the standard dilatometer are more representative of an elasto-plastic response.

The pore water pressure of soil samples taken from the Wildlife site in Imperial Valley, California were used to evaluate the performance of piezometers. Pore pressure transducers were installed at various depths of the soil layer where liquefaction is expected to occur during strong ground motions. Measurements from the Wildlife site reveal that the piezometer response was slow when compared to other field and laboratory piezometer measurements.

Analytical expressions are assessed for the calculation of backfill pressure in retaining wall construction. Subjects include planar shear surfaces, arbitrarily stratified soil deposits, differing degrees of soil saturation and external loading.

The objective of this work is to perform an analysis of pressure distributions in grain silos for both the discharge and static conditions with eccentric outlets. To this end, the commercial ANSYS program, based on the finite-element method is employed. In this paper, results are presented for a silo with a height of 10.5 m (cylinder height 8 m, base cone height 2.5 m), a silo radius of 3 m, and an outlet radius of 0.5 m. Outlet eccentricity ranged from 0% (central outlet) to 100% (maximally eccentric outlet, tangential to the silo cylinder). Based on the results, this paper proposes new methods of analyzing silo discharge and the influence of outlet eccentricity. The discharge model combines both dilatancy and type of discharge effects. 3D models were developed to analyze the eccentricity of the outlet. The results are compared with previous research data and with standard design guidelines.

Measured barometric pressure fluctuations in a borehole drilled 600 m into the unsaturated zone at a site on the eastern slope of Yucca Mountain, Nevada, are used to compute pneumatic diffusivities and air permeabilities of layered tuffaceous rocks. Of particular interest is the occurrence of increasing pressure amplitude and decreasing phase lags observed at several deep stations. The pressure amplitude increases by 13% and the pressure peak arrives 65 to 72 h earlier as the depth of the unsaturated zone increases from 407 to 436 m. This observation is inconsistent with a conventional 1D downward pressure decay model, but can be explained by hypothesizing the existence of a lateral pneumatic flow path from a nearby fault. A 2D numerical model has been constructed to test this lateral flow hypothesis. The modeling results indicate that a leaky-fault hypothesis can reconcile the measured barometric data with other geologic mapping and permeability measurements at the site. The inferred fault permeability ranges from 0.6 X [10.sup.-2] to 0.12 X [10.sup.-9] [m.sup.2], and that of the surrounding tuff layers ranges from 0.4 X [10.sup.-13] to 0.8 X [10.sup.-12] [m.sup.2]. Our analysis also demonstrates that although the larger-amplitude, longer-period synoptic signals lack coherence and periodicity, determination of air permeability in deep unsaturated zones must rely on these longer-period oscillations of barometric pressure whose periods are on the order of weeks to months because the shorter-period diurnal and semidiurnal barometric oscillations generally are not detectable at deep depths.

The contact pressure arising when a flat-ended punch is loaded against an elastic half-plane with a thin, rigid-ideally plastic interlayer is found under adhesive conditions. Slip line field theory is employed, and the local stress state in the substrate deduced in order to assess the brittle fracture strength of the material beneath the contact.