Ultimate Lateral Resistance of Pile Groups in Sand

Experimental investigations on model pile groups of configuration 1 × 1, 2 × 1, 3 × 1, 2 × 2, and 3 × 2 for embedment length-to-diameter ratios L∕d = 12 and 38, spacing from 3 to 6 pile diameter, and pile friction angles δ = 20° and 31°, subjected to lateral loads, were conducted in dry Ennore sand obtained from Chennai, India. The load-displacement response, ultimate resistance, and group efficiency with spacing and number of piles in a group have been qualitatively and quantitatively investigated. Analytical methods have been proposed to predict the ultimate lateral capacity of single pile and pile groups. The proposed methods account for pile friction angle, embedment length-to-diameter ratio, the spacing of piles in a group, pile group configuration, and soil properties. These methods are capable of predicting the lateral capacity of piles and pile groups reasonably well as noted and substantiated by the comparison with the experimental results of the writers and other researchers.     

Mechanics of Lateral Spreading Observed in a Full-Scale Shake Test

This paper examines in detail the mechanics of lateral spreading observed in a full-scale test of a sloping saturated fine sand deposit, representative of liquefiable, young alluvial and hydraulic fill sands in the field. The test was conducted using a 6-m tall inclined laminar box shaken at the base. At the end of shaking, nearly the whole deposit was liquefied, and the ground surface displacement had reached 32 cm. The presented analysis of lateral spreading mechanics utilizes a unique set of lateral displacement results, DH, from three independent techniques. One of these techniques—motion tracking analysis of the experiment video recording—is especially useful as it produced DH time histories for all laminar box rings and a complete picture of the lateral spreading initiation with an unprecedented degree of resolution in time and space. A systematic study of the data identifies the progressive stages of initiation and accumulation of lateral spreading, lateral spread contribution of various depth ranges and sliding zones, their relation to the simultaneous pore pressure buildup, and the soil shear strength response during sliding.     

Monotonic Lateral Loading of Piles in Calcareous Sand

This paper describes the results of a centrifuge modeling study of the response of piles embedded in calcareous sand under monotonic lateral loading. A number of features have been explored, including method of installation, rate of loading, and pile head restraint. The study has led to recommendations for load-transfer curves with the magnitude of lateral resistance linked to the soil strength through the cone resistance. Modification factors have been developed to allow for different methods of installation and for different rates of loading. The proposed load-transfer curves and resulting pile response are shown to provide an excellent match with the experimental data, and are compared with results derived using existing guidelines for terrigenous sands. Significant differences are demonstrated, confirming the need to treat calcareous sediments separately from other soil types with respect to lateral pile response.     

Pipe-Soil Interaction Model Incorporating Large Lateral Displacements in Calcareous Sand

The use of the plasticity theory offers an attractive framework to encapsulate the behavior of a pipe and the underlying soil in terminology consistent with pipeline structural analysis. Models that express the pipe-soil behavior purely in terms of the loads on a segment of pipe and the corresponding displacements have been suggested, although verification with geotechnical centrifuge experiments has been limited to relatively small lateral displacements (i.e., less than two pipe diameters). Over larger movements, the berms that build up alongside the pipe affect the load-displacement behavior, with existing strain-hardening plasticity models incapable of simulating this transition. This technical note provides experimental evidence of pipe-soil behavior for lateral displacements for up to five diameters. It further presents observations from 20 centrifuge experiments of a prototype 1-m-diameter pipe in calcareous sand. The results are used to validate the modification of a pipe-soil model to include the horizontal displacement hardening of the yield surface. Retrospective numerical simulations of the centrifuge experiments verify the modified model’s performances for lateral displacements of up to five diameters which was also the extent of the centrifuge experiments. This incorporation of large lateral displacements has significant application in on-bottom stability analysis as displacement-based design becomes more prevalent.     

Permanent Strains of Piles in Sand due to Cyclic Lateral Loads

The strain superposition concept, proposed for ballast study, is applied here to evaluate strain accumulation for laterally loaded piles in sand. It is shown that the soil properties, types of pile installation, cyclic loading types, pile embedded length, and pile∕soil relative stiffness ratio are important factors that influence the pile behavior under mixed lateral loads. These factors are quantified by means of a degradation factor, t, which is derived from the results of 20 full-scale pile load tests and then verified using 6 additional full-scale pile load tests.     

Base Resistance of Jacked Pipe Piles in Sand

The paper presents the results from an experimental program carried out at Trinity College Dublin, in which instrumented model piles were jacked into loose dry sand in a large testing chamber. A number of pile installations were carried out to study the effects of in situ stress, diameter, and wall thickness on the behavior of open-ended piles in sand. These indicated that plug stiffness and capacity may be expressed as simple functions of the cone penetration test end resistance and the incremental filling ratio prior to loading. The magnitude and distribution of shear stresses measured on the inner wall are shown to be compatible with existing experimental data and can be related directly to the stress level, interface friction angle, and dilation of the sand at the pile wall. The data are shown to facilitate a better understanding of the factors controlling plug resistance.     

LMPL—300液化装置的技术特点

介绍了宝普公司ＬＭＰＬ－３０６液化装置概况，较详细介绍和分析了流程和流程特点，进行了装置主要性能指标计算，并结合操作分析了其控制特点，以及变工况生产特点．     

Water Film in Liquefied Sand and Its Effect on Lateral Spread

A 1D saturated sand layer of 2 m in thickness, in which a silt seam is sandwiched, is liquefied by an instant shock. It is found that a water film is easily formed beneath the silt seam with a thickness as thin as a few millimeters just after liquefaction in loose sand and that the film lasts longer than the post-liquefaction settlement. The effect of the water film on pore-pressure distribution and sand settlement is intensively studied. 1g shake table tests are then carried out for 2D models with or without seams of silt within a saturated sand layer. In the former case, water films formed beneath silt seams just after liquefaction enable the soil mass above them to glide due to an unbalanced force along the water films, not only during but also after shaking. In the latter case, the soil deforms continuously, mostly during shaking, and stops afterward. Thus, a significant effect of water films formed beneath thin, low-permeability sublayers in a liquefied loose sand, on the failure mode and timing in lateral spread, is clearly demonstrated by these simple model tests.     

Lateral and Upward Soil-Pipeline Interactions in Sand for Deep Embedment Conditions

The soil–pipeline interactions in sand under lateral and upward movements are investigated with particular attention to the peak forces exerted on the pipe. The analytical solutions for estimating the peak forces are summarized and it is shown that, for deep embedment condition, there is large uncertainty in the true values since the bounds established by the analytical solutions are large. In order to find the solution for the peak force and to investigate its transition from shallow to deep failure mechanism, finite element analyses of lateral and upward pipe movements are performed for different embedment conditions. Two different soil models (Mohr–Coulomb and Nor–Sand models) are used for the simulations. The accuracy of the analysis is first examined by simulating experimental tank tests. The analysis is further extended to deeper embedment ratios of as large as 100. The obtained finite element results are used to construct a design chart for deep embedded pipelines.     

Behavior of Step Tapered Bored Piles in Sand under Static Lateral Loading

The behavior of step tapered bored piles in sand, under static lateral loading, was examined by field tests at one site in Kuwait. A total of 14 bored piles including two instrumented piles were installed for lateral loading. The soil profile consists of medium dense sand with weak cementations and no groundwater was encountered in the boreholes. Laboratory tests were carried out to determine the basic soil characteristics and the strength parameters. Both the ultimate lateral capacity and the deflections at applied loads were examined. The results indicate increased lateral load carrying capacity and decreased deflections at different applied loads for the step tapered piles due to the enlargement or strengthening of the upper section of the piles. The advantages of using this type of pile is emphasized including the cost saving resulting from an economical design.     

Seismic Performance of a River Dike Improved by Sand Compaction Piles

Sand compaction piling is one of the commonly used countermeasures for earthquake liquefaction hazard of river dikes. This paper presents a case study of the performance of an instrumented dike in northeast Japan that was improved by sand compaction piles and subjected to the 2003 Northern Miyagi Earthquake, with the aim to better understand the effectiveness of this ground improvement method. Simulation has been carried out by means of a fully coupled numerical procedure which employs a sophisticated cyclic elastoplastic constitutive model and the updated Lagrangian algorithm. Comparisons between the field measurements and the computed responses, including the time histories of accelerations and pore-water pressures at different locations, show reasonably good agreement. Numerical simulation has also been made of the same dike but without ground improvement to identify the effects of sand compaction piles in altering the performance of the dike. The study demonstrates that the comprehensive numerical procedure is a promising tool for development of seismic performance-based design of earth structures.     

Lateral Resistance of Full-Scale Pile Cap with Gravel Backfill

A static lateral load test was performed on a full-scale 3×3 pile group driven in saturated low-plasticity silts and clays. The steel pipe piles were attached to a concrete pile cap which created a “fixed-head” end constraint. A gravel backfill was compacted in place on the backside of the cap. Lateral resistance was therefore provided by pile–soil–pile interaction, as well as base friction and passive pressure on the cap. In this case, passive resistance contributed about 40% of the total resistance. The log–spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine method significantly underestimated the resistance while the Coulomb method overestimated resistance. The cap movement required to fully mobilize passive resistance in the gravel backfill was about 6% of the cap height. This is somewhat larger than reported in other studies likely due to the underlying clay layer. The p-multipliers developed for the free-head pile group provided reasonable estimates of the pile–soil–pile resistance for the fixed-head pile group once gaps adjacent to the pile were considered.     

直流法测量钯氢化物电极电阻时的阻值偏移

讨论了直流法在线测量钯氢化物电极电阻时的电化学效应，计算了电解液的共导、测量电流与电解电流引起的浓差电池效应以及电极作为集流体引起的电阻贡献。结果表明：当电极具有高的长度与半径比值、粗糙的表面、高的溶液电导以及大的电解电流时容易引起显著的附加电阻。     

液化装置的工质替代

１概述天津石化公司空分厂界内一套液化装置，由四川空分设备集团２００２年设计制造，型号YPON－１８７５／２７９０，带冰机中压流程，可同时生产液氮、液氧（用液氮液化气氧），或选择单独生产其中一种产品，生产能力５０t／dLO２或５４t／dLN２。本厂KDON－１５００／３０００型分子筛流程空分装置为之提供气源。目前，设备处于试生产阶段。本厂生产、供气及液化设备运行有如下几个特点：（１）空分装置氮气产量与需求量相比，略显不足，多数情况下有缺口。（２）液氧产品市场情况相比液氮而言更好。（３）在试生产阶段，液化装置…     

Lateral Resistance of Single Pile Located Near Geosynthetic Reinforced Slope

An extensive program of laboratory tests was carried out to study the effect of reinforcing an earth slope on the lateral behavior of a single vertical pile located near the slope. Layers of geogrid were used to reinforce a sandy slope of 1 (V):1.5 (H) made with sands of three different unit weights representing dense, medium dense, and loose relative densities. Several configurations of geogrid reinforcement with different numbers of layers, vertical spacing, and length were investigated. The experimental program also included studies of the location of pile relative to the slope crest, relative density of sand, and embedment length of pile. The results indicate that stabilizing a soil slope has a significant benefit of improving the lateral load resistance of a vertical pile. The improvement in pile lateral load was found to be strongly dependent on the number of geogrid layers, layer size, and relative density of the sand. It was also found that soil reinforcement is more effective for piles located closer to the slope crest. Based on test results, critical values are discussed and recommended.     

Increasing the Resistance of Piles Subject to Cyclic Lateral Loading

Small-scale tests were carried out on a monopile and fin piles to determine the effect the length of fins had upon the lateral displacement of cyclically loaded piles. A variety of loading conditions were applied to model piles in a dense sand by using a mechanical loading system. Ten thousand cycles were used in each test to represent 20 years of environmental loading on offshore structures. Variables included the magnitude, frequency, and direction of the load; the type of pile tip; and the length of the fins. The reduction in pile head displacement was used as a measure of the efficiency of the fins. The tests show that the fins reduced the lateral displacement by at least 50% after 10,000 cycles.     

Increased Lateral Abutment Resistance from Gravel Backfills of Limited Width

Lateral pile cap tests were performed on a pile cap with three backfills to evaluate the static and dynamic behavior. One backfill consisted of loose silty sand while the other two consisted of 0.91- and 1.82-m-wide dense gravel zones between the pile cap and the loose silty sand. The 0.91- and 1.82-m-wide dense gravel zones increased the lateral resistance by 75 to 150% and 150 to 225%, respectively, relative to the loose silty sand backfill. Despite being thin relative to the overall shear length, the 0.92- and 1.82-m-wide gravel zones increase lateral resistance to approximately 54 and 78%, respectively, of the resistance that would be provided by a backfill entirely composed of dense gravel. The dynamic stiffness for the pile cap with the gravel zones decreased about 10% after 15 cycles of loading, while the damping ratio remained relatively constant with cycling. Dynamic stiffness increased by about 10 to 40% at higher deflections, while the damping ratio decreased from an initial value of about 0.30 to around 0.26 at higher deflections.     

Resistance of Membrane Retrofit Concrete Masonry Walls to Lateral Pressure

This paper first describes the current state of analysis for the response of unreinforced concrete masonry walls subjected to lateral uniform pressure. The formulation is based on the initial elastic response, the subsequent initiation of cracks and the nonlinear rocking response, and the eventual large displacement and potential collapse. The necessary equations are developed for these phases in the form of a resistance function. The paper then incorporates membrane retrofit materials to strengthen the wall’s resistance to lateral pressure, and develops the necessary resistance function equations. In blast tests, membrane retrofit unreinforced masonry walls have experienced severe cracking and large displacements without collapse. This is of high interest to the Department of Defense, the protection of diplomatic facilities, and the construction industry impacted by hurricanes and other high wind events. The paper concludes with examples that demonstrate application of membrane retrofits indeed increase the resistance of the wall to lateral pressure.     

液化装置安全经济运行经验

根据液化装置开、停机及运行过程中,出现的冷箱管道漏液、热端温差大、影响中压氮气管网纯度等事件,进行分析处理,优化操作,使设备更加安全经济运行。