Pile Surface Research Articles

The Diavik Waste Rock Project: Implications of wind-induced gas transport

Wind-induced gas transport in a test-scale unsaturated waste rock pile was investigated at the Diavik diamond mine, Northwest Territories, Canada. Differential gas pressures were measured in 2008 at 49 locations within a field-scale experimental waste rock pile (test pile) and at 14 locations on the surface of the test pile at 1-min intervals. Wind speed and direction were measured at 10-min intervals and decomposed into north, south, east, and west vectors. Correlations between wind vectors and pressure measurements indicate that the wind influences pressure fluctuations in the test pile. The strength of the correlation is roughly inversely proportional to the distance between the measurement ports and the atmospheric boundary. The relationship between the magnitude of the wind vector and pressure fluctuations on the surface of the test pile is non-linear. However, the relationship between internal and surface pressure measurements is linear, suggesting that gas flow within the test pile follows Darcy’s Law. Spectral analysis demonstrates that the dominant periods of the wind range from 1 to 14d. A 1-D analytical solution to the flow equation is used to demonstrate that long periods have the most pronounced effect on transient gas flow within the test pile and that the penetration depth of the wind-induced gas pressure wave is a function of wind period and permeability of the test pile.

A comparison of three methods for the quantification of greenhouse gas emissions from spontaneous combustion in open-cut coal mines

Greenhouse gas emissions from spontaneous combustion in coal mines are currently excluded from national inventories by the United Nations Framework Convention on Climate Change because there are no robust methods available to quantify the emissions. This article reports on investigations of three approaches being pursued with the aim of developing methods which are sufficiently robust to enable these emissions to be included in inventories. The first method was based on the use of airborne thermal infrared photography coupled with chamber measurements of emissions from hot mine spoil pile surfaces. In the second method, crosswind traverses of the plume using an instrumented vehicle were used to estimate the emission fluxes. The third method was based on inverse atmospheric modelling using stationary CO2 monitors. All three methods showed considerable scatter in their estimates but also showed appreciable overlap. While the three methods used in this study have shown convergence, there is still considerabl...

Online monitoring of volatile organic compound production and emission during sewage sludge composting

The production and emission of volatile organic compounds (VOCs) were studied using an online monitoring method in a well-operated sludge composting plant. Results indicated that VOC production within the pile was different from emission at the pile surface. The total mass of VOC production was 1.09gCkgDM−1, which was 2.3 times as high as the total mass of emission. The maximum production and emission masses occurred in the mesophilic phase of composting and were 444 and 202mgkgDM−1d−1, respectively. VOC production and emission rates also varied rapidly at different times. The relationship of VOC production rates and time in an on/off aeration cycle at different periods could be expressed as a quadratic equation, while the emission rate could be expressed as a linear equation.

Procedure for determination of the stiffness coefficients of soil in analyzing the horizontal loading of piles

An approach to analysis of piles for horizontal loading on the basis of a model of an elastic, linearly deformable medium is examined. A procedure obtained on the basis of elastic solutions is presented for determination of the proportionality factor describing the linear increase in the coefficient of stiffness of the soil along the lateral surface of a pile. Recommendations, which are contained in standards regulating assignment of the proportionality factor, and which are proposed by the author are analyzed. Formulas are presented for back calculation of the proportionality factor based on data derived from field tests of piles under a horizontal load.

Uplift Behavior of Vertical Piles Embedded in Oil-Contaminated Sand

AbstractThere are several problems when dealing with oil-contaminated soil that affect environmental quality and alter the geotechnical properties of the soil. The influence of oil contamination on the uplift performance of model concrete piles embedded in sand at various densities is investigated. In this study, the model parameters are varied, namely, the thickness and diameter of the contaminated layer, type of oil contamination, pile surface roughness, and pile installation method. Contaminated-sand layers were prepared by mixing the sand with an oil content of 0–3% with respect to dry soil to match the field conditions. The results were then analyzed to study the effect of each parameter. To evaluate the scale effects, two sizes of model piles were tested, and the results were compared. This paper also discussed the effect of oil contamination on the relative ground movement around the pile surface. The results indicated that the uplift resistance was drastically reduced by oil contamination. The max...

Prediction of the shaft resistance of nondisplacement piles in sand

SUMMARYUsing pile segment analysis, the mobilized shaft resistance of axially loaded nondisplacement piles in sand is investigated here. It is accepted that the shaft capacity of piles constructed in granular soils is highly influenced by the mechanical behavior of soil–structure interfaces forming adjacent the piles skin. Adopting the thin interface layer as a load transfer mechanism, a simple but accurate critical state compatible interface constitutive model is introduced. After evaluation, the interface model in conjunction with the pile segment analysis is applied for the prediction of the shaft resistance mobilized in nondisplacement piles. The proposed approach takes into account the influences of pile diameter and surface roughness together with the effects of the surrounding soil density and stiffness on the mobilized shaft resistance. The performance of the proposed method is verified by comparing its predictions with the experimental data of various model piles covering wide ranges of length, diameter, roughness, and surrounding soil properties. Copyright © 2012 John Wiley & Sons, Ltd.

인공신경망을 활용한 동착강도 예측

동착강도는 동토지반 말뚝기초 설계시 지지력을 결정하는 주요 설계정수이다. 동착강도는 동결온도, 구속응력, 말뚝표면 특성, 토사종류 등 다양한 인자들에 의해 동시다발적인 영향을 받는 것으로 보고되고 있다. 하지만 동착강도에 대한 연구는 소수의 인자들만 반영할 수 있는 실험연구를 중심으로 수행되어온 경향이 있으며, 설계정수로서 동착강도를 산정하기 위한 방법들은 동결온도, 말뚝재료 등의 주요 인자들만을 고려할 수 있는 한계가 있어 왔다. 본 연구는 인공신경망 이론을 동착강도 산정에 활용함으로서 다양한 영향인자 조건에서 동착강도를 예측할 수 있는 방안을 모색하기 위한 목적으로 수행되었다. 인공신경망 학습을 위하여 총 5종류의 연구사례로부터 137개의 자료를 수집하였으며, 그 중 100개를 학습자료로, 37개를 실증자료로 구분하였다. 연구결과 단계적 인공신경망 학습을 통하여 동착강도 산정 시 다양한 영향인지를 다차원적으로 고려하여 예측하는 방법이 병행되어야 할 필요성을 확인하였으며, 5개 영향인자를 동시에 고려하여 동착강도를 예측할 수 있는 신뢰성 높은 학습결과를 도출 및 검증하였다. 또한, 매개변수 연구결과 동착강도는 동결온도와 말뚝재료의 변화에 가장 민감하게 반응하는 것으로 나타났고 수직응력에 의한 영향은 일부 온도구간에서만 뚜렷하게 나타나며 토사종류와 재하속도의 변화에 따라 동착강도가 증가하는 경향이 변화하는 특성을 나타내었다. Adfreeze bond strength is a primary design parameter, which determines bearing capacity of pile foundation in frozen ground. It is reported that adfreeze bond strength is influenced by various affecting factors like freezing temperature, confining pressure, characteristics of pile surface, soil type, etc. However, several limited researches have been performed to obtain adfreeze bond strength, for past studies considered only few affecting factors such as freezing temperature and type of pile structures. Therefore, there exists a limitation of estimating the design parameter of pile foundation with various factors in frozen ground. In this study, artificial neural network algorithm was involved to predict adfreeze bond strength with various affecting factors. From past five studies, 137 data for various experimental conditions were collected. It was divided by 100 training data and 37 testing data in random manner. Based on the analysis result, it was found that it is necessary to consider various affecting factors for the prediction of adfreeze bond strength and the prediction with artificial neural network algorithm provides enough reliability. In addition, the result of parametric study showed that temperature and pile type are primary affecting factors for adfreeze bond strength. And it was also shown that vertical stress influences only certain temperature zone, and various soil types and loading speeds might cause the change of evolution trend for adfreeze bond strength.

동결토 전단강도를 활용한 동착강도 산정에 관한 연구

동토기반 말뚝기초의 지지력은 말뚝구조물 표면과 주변 토사의 접촉면에서 발현되는 동착강도에 의해 산정되며, 이는 동착-강도가 동토지반 기초설계를 위한 가장 주요한 설계정수임을 의미한다. 동착강도는 토사종류, 동결온도, 말뚝표면에 수직방향으로 작용하는 지중응력, 재하속도, 말뚝구조물의 표면 거칠기 등 다양한 인자들에 동시다발적인 영향을 받는 것으로 보고되고 있다. 1960년대부터 동토지반 기초설계를 위한 동착강도 산정방법들이 제안되어 왔으나, 대부분 동결온도와 말뚝구조물 표면특성에 대한 영향은 고려하고 있는 반면 동착강도의 주요 영향인자 중 하나인 지중응력에 의한 영향을 고려하지 않고 있어 소정깊이 이상의 말뚝기초 설계를 위한 동착강도 산정방법으로 활용되기에는 한계가 있는 것으로 판단된다. 본 연구에서는 동결온도뿐 아니라 지중응력이 동착강도에 미치는 영향을 파악하기 위하여 직접전단시험기를 활용한 동결토 전단강도 및 동착강도 측정실험을 각각 수행하였다. 실험결과 전단강도와 동착강도는 모두 동결온도 조건이 낮아질수록, 혹은 수직응력 조건이 커질수록 증가하는 경향을 보였다. 전단강도와 동착강도의 정량적 관계분석을 위해 정의된 전단강도와 동착강도의 비 <TEX>$r_s$</TEX>는 초기 동결온도에서는 급격하게 감소하는 경향을 나타냈으나, 동결온도가 낮아질수록 증가하며 수렴구간을 형성해가는 경향을 보였다. 본 연구에서는 최종적인 연구결과로서 동결온도 및 수직응력 조건을 바탕으로 결정된 <TEX>$r_s$</TEX>값을 이용하여 동결토의 전단강도로부터 동착강도를 예측할 수 있는 방법을 제안하고 있다. Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. It denotes that adfreeze bond strength is the most important design parameter for foundations in cold region. Adfreeze bond strength is affected by various factors like 'soil type', 'frozen temperature', 'normal stress acting on soil/pile interface', 'loading rate', 'roughness of pile surface', etc. Several methods have already been proposed to estimate adfreeze bond strength during past 50 years. However, most methods have not considered the effect of normal stress for adfreeze bond strength. In this study, both freezing temperature and normal stress have been controlled as primary factors affecting adfreeze bond strength. A direct shear box was used to measure adfreeze bond strength between sand and aluminum under different temperature conditions. Based on the test results, the relation between shear strength of frozen sand and adfreeze bond strength have been investigated. The test results showed that both of shear strength and adfreeze bond strength tend to increase with decreasing frozen temperature or increasing confining pressure. The ratio of shear strength and adfreeze bond strength, expressed as <TEX>$r_s$</TEX>, decreased initially frozen section but increased at much lower frozen temperature and there were uniform intervals under the different normal stress conditions. A method for predicting adfreeze bond strength using <TEX>$r_s$</TEX> has finally been proposed in this study.

동결온도와 수직구속응력 변화에 따른 모래와 알루미늄 재료의 접촉면에서 작용하는 동착강도 실험 연구

Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. Adfreeze bond strength is considered to be the most important design parameter for foundations in cold region. Many studies in last 50 years have been conducted to analyze characteristics of adfreeze bond strength. However, most studies have been performed under constant temperature and normal stress conditions in order to analyze affecting factors like soil type, pile material, loading speed, etc. In this study, both freezing temperature and normal stress acting on pile surface were considered to be primary factors affecting adfreeze bond strength, while other factors such as soil type, pile material and loading speed were predefined. Direct shear box was used to measure adfreeze bond strength between Joomoonjin sand and aluminium because it is easy to work for various roughness. Test was performed with temperatures of > , , , , and and vertical confining pressures of 1atm, 2atm, and 3atm. Based on the test results, the effects of temperature and vertical stress on adfreeze bond strength were analyzed. The test results showed that adfreeze bond strength increases with decreased temperature and increased vertical stress. It was also noted that two types of distinct sections exist, owing to the rate of increase of adfreeze bond strength along the change of freezing temperature: 1)rapidly increasing section and 2)gradually decreasing section. In addition, the results showed that a main factor affecting adfreeze bond strength switches from friction angle to adhesion as freezing temperature decreases.

Size segregation mechanism of binary particle mixture in forming a conical pile

The mechanism of particle segregation in forming a conical pile or centrally filling a cylindrical vessel is investigated by applying a Shinohara et al.'s Screening Layer model (1972, 1984 and 1990), where the segregation patterns were measured by a tube-sampling experiment and a DEM simulation. The distribution of mixing ratio of a segregating component of different sizes can be drawn along the pile surface and well correlated with each other for the first time. As a result, the zone, where the segregating component of smaller particle is contained around a central feed point, was found to expand by an increment of the initial mixing ratio, the volumetric feed rate and the flow length of the pile surface. These characteristics are governed by flowability parameters such as velocity ratio, penetration rate and packing rate of the segregating component, which are affected by operating conditions besides particle properties and are to be delved into further. In spite of complicated avalanche phenomena of particles exhibited around the flowing head along the conical pile surface, the present model description consisting of the material balance within the flowing layer was found to be satisfactory in practice with the verifications from the experiments and the microscopic DEM simulation.

Uplift Capacity of Belled and Multi-Belled Piles in Dense Sand

This paper evaluates the uplift capacity of belled and multi-belled piles in dense sand. A two-dimensional distinct element (DE) analysis was applied in pullout tests on single piles to investigate the uplift resistance of the piles, the soil behavior around the piles, and the interaction between the soil and the pile surface. It was observed from the DE analysis that the soil mass adjacent to the projections of the belled and multi-belled piles moved vertically, and that the soil movements leaned slightly with the occurrence of relative displacement between the soil and the pile surface. A theoretical solution for predicting the uplift capacity of belled and multi-belled piles was derived from an upper bound limit analysis based on the soil movements in the DE analysis. The solution was able to reproduce the ultimate uplift resistance in the DE analysis using the friction angles in the aggregates and on the pile surface that were evaluated from a simulation of direct and simple shear tests. In addition, a continuity equation that satisfied the relationship between the displacement vector of the soil mass adjacent to the projections and the change in volume around the soil mass was proposed for predicting the uplift capacity of actual piles under axisymmetric conditions. The theoretical solution obtained with the continuity equation was in good agreement with the pullout resistance of the belled and multi-belled piles in centrifuge model tests and full-scale tests conducted in situ.

Model Test of Roughness’ Influence on Bearing Mechanism in Rock-Socketed Pile

The interface roughness between pile and rock in rock-socketed pile can influence its bearing mechanism largely. At present the numerical simulation, which simulates the interface roughness with changing the surface shape or interface friction coefficient, is used to study the interface roughness’ influence on pile’s bearing mechanism. It can reveal the pile bearing mechanism in some degree; however, there are some defects and limitations in simulation because of its assumptions and simplifications. Based on the pile foundation of Tian-xing-zhou Bridge, the model test is conducted to study the interface roughness’ influence on rock-socketed pile bearing mechanism. In the model test, the surface of model piles are made different ranging from smooth to rough, and the bed rock is simulated with mixture of sand and plaster, the rock-soil overlain the bed rock is simulated with silty sand, the pile is simulated with organic glass rod according to similarity principle respectively. The results show that load-settlement curves grow more gently, the ultimate bearing capacity is bigger, the proportion of point resistance is lower, and the shaft resistance is bigger which reaches more than 70% of total loading as the surface of pile is rougher. The conclusions are useful to deciding the length of pile foundation in Tian-xing-zhou Bridge.

Influence of Vibration on Interface Friction of Pile-Soil System

Based on the model of effective friction coefficient, the change tendency of effective friction coefficient under different harmonic forces and the method of improving its decrease rate have been studied. The model of vibratory piling machine has been taken as a research object for friction reduction, and the stress of soil particles and the situation of friction resistance on pile surface have been analyzed while sinking the pile. The effect on interface friction of pile-soil system under vibration, caused by the depth of pile sinking, pile structure parameters and vibration acceleration, has also been studied, so that an effective method of decreasing interface friction can be found. Thus, the sinking efficiency would be improved by being analyzed, evaluated and parameter optimized.

On the Design of Instrumented Double-Wall Model Piles Used to Investigate Plugging of Open-Ended Pipe Piles

Abstract Plugging of open-ended pipe piles during installation and loading is an important phenomenon with substantial effects on pile capacity. This paper offers a number of comments related to the design of instrumented double-wall pipe piles that are becoming increasingly popular in research. A double-wall pile consists of two concentric thin-wall cylinders that are rigidly fixed at the top and are free to strain independently of one another elsewhere, with the pile shoe attached to one of the cylinders. Instrumentation that permits defining the state of the stress around the pile is installed between the two cylinders. Pile geometry, location of pile shoe, protection of sensors, radial stress measurements, and pore water pressure measurements are discussed. Measurements indicate that when a pile plugs, load is transferred by arching to the inner pile surface within the first two pile diameters. The data also indicates that a surge in pore water pressure occurs with each hammer blow, which results in a reduction of effective stress and subsequent pile setup.

Culture-Independent Phylogenetic Analysis of the Microbial Community in Industrial Sugarcane Bagasse Feedstock Piles

Sugarcane bagasse is an important lignocellulosic by-product with potential for conversion to biofuels and chemicals in biorefinery. As a step towards an understanding of microbial diversity and the processes existing in bagasse collection sites, the microbial community in industrial bagasse feedstock piles was investigated. Molecular biodiversity analysis of 16S rDNA sequences revealed the presence of a complex bacterial community. A diverse group of mainly aerobic and facultative anaerobic bacteria was identified reflecting the aerobic and high temperature microenvironmental conditions under the pile surface. The major bacterial taxa present were identified as Firmicutes, Alpha- and Gammaproteobacteria, Acidobacteria, Bacteroidetes, and Actinobacteria. Analysis of the eukaryotic microbial assemblage based on an internal transcribed spacer revealed the predominance of diverse cellulolytic and hemicellulolytic ascomycota. A microbial interaction model is proposed, focusing on lignocellulose degradation and methane metabolism. The insights into the microbial community in this study provide a basis for efficient utilization of bagasse in lignocellulosic biomass-based industries.

Oxygen and Carbon Dioxide Distribution And Movement in Passively Aerated Compost Piles

Distributions of O2 and CO2 concentrations across a cross section of a full-scale passively aerated, mechanically turned, compost piles were measured as a function of time over an 11 day long period covering two pile turnings. The compost pile had a triangular cross section, was 1.8 m high, 4.4 m wide, 80 m long and consisted of sewage sludge, yard/park waste and screening residue from previously composted materials. The measurements were conducted in one cross section of the pile. The O2 and CO2 concentration measurements were used in combination with earlier published measurements of air permeability and air pressure inside the compost pile to calculate O2 and CO2 fluxes across the pile surface as functions of time and location as well as estimation of total specific oxygen consumption rates in the compost. Distributions of O2 and CO2 concentrations inside the pile were relatively constant with time and exhibited high O2 concentrations near the surface and high CO2 concentrations near the center of the pile. Maximum O2 fluxes in the compost occurred along the lower edges of the pile and equalled up to 15 kg/m−2 h−1 while maximum CO2 fluxes occurred at the center top of the pile and equalled up to 700 g m−2 h−1. Average daily CO2 emissions from the compost were up to 3.4 kg m3 d−1 while the corresponding O2 flux into the compost pile was up to 53 kg m3 d−1. Average O2 consumption was 1.4 kg m−3 d−1 while average CO2 production was 1.5 kg m−3 d−1 at the measurement location over the 11 day experimental period.

Minimizing profile error when estimating the sieve-size distribution of iron ore pellets using ordinal logistic regression

Size measurement of pellets in industry is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of pellet size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. We evaluate the statistical significance of the ability of commonly used size and shape measurement methods to discriminate among different sieve-size classes using multivariate techniques. Literature review indicates that earlier works did not perform this analysis and selected a sizing method without evaluating its statistical significance. Backward elimination and forward selection of features are used to select two feature sets that are statistically significant for discriminating among different sieve-size classes of pellets. The diameter of a circle of equivalent area is shown to be the most effective feature based on the forward selection strategy, but an unexpected five-feature classifier is the result using the backward elimination strategy. The discrepancy between the two selected feature sets can be explained by how the selection procedures calculate a feature's significance and that the property of the 3D data provides an orientational bias that favours combination of Feret-box measurements. Size estimates of the surface of a pellet pile using the two feature sets show that the estimated sieve-size distribution follows the known sieve-size distribution.

Behavior of vertical piles embedded in reinforced sand under pullout oblique loads

The behavior of vertical single piles embedded in reinforced and non-reinforced cohesionless soil has been investigated with the help of small-scale model tests. These piles were installed in sand of different relative densities (<i>D_r</i> = 30 and 60%) and subjected to pullout loads of different inclinations. The model pile pullout tests were conducted using three reinforced concrete circular piles with different surface conditions (smooth, smooth with necking and bulging, and rough). The influence of sand reinforcement with geogrid on the uplift performance of the model piles was investigated. These investigations were carried out by varying the inclination of the pullout load, the embedded depth of reinforcement, the number of reinforcement layers, and the length of the reinforcement layer. The test results show that the pullout resistance increases with the concrete surface roughness, sand density and the inclusion of a reinforcing layer. It was also found that the effectiveness of the reinforced layer is dependent on the concrete surface roughness. This paper also discusses the effects of these parameters on the relative ground movement near the pile surface.

Uplift Capacity of Axially Loaded Piles in Clays

The present study aims at determining the uplift capacity of axially loaded piles in clays whose undrained cohesion increases linearly with depth. With the application of the axisymmetric static limit analysis approach, proposed recently by the writers, the variation of the nondimensional uplift factors with respect to changes in the embedment ratio (H/B) has been obtained for several rates of increase of soil cohesion with depth defined in terms of a nondimensional factor m for given values of soil cohesion (c0) along the ground surface and diameter (B) of pile. The uplift resistance has been evaluated in the form of the uplift factors, Fcb and Fct due to the components of the shaft resistance and the total resistance, respectively. For the given values of c0 and B, the magnitude of the uplift resistance increases continuously with an increase in the value of m. Furthermore, the Fcb values are found to remain unaffected with the variation in the shaft adhesion, whereas, the Fct values increase continuously with an increase in the adhesion factor of the pile shaft.

Studies of long-term storage of high quality raw sugar

Although existing contracts do not provide sufficient economic justification to increase raw sugar quality, the trend of manufacturing better quality raw sugar in the factories will likely continue. Relatively few studies have been conducted on storage of VHP (very high pol) and VLC (very low color) sugars, especially when the storage period approaches 9–10 months. Monitoring of commercial sugar shipments indicated that, after an initial relatively safe period of storage, sugar color might double or even triple in a short period of time. Large experimental piles of VHP and VLC sugar were monitored in two sugar factories with different crystallization sequences (conventional and double magma) for two consecutive seasons. Temperature and relative humidity probes were placed up to 15 m inside the piles. Samples were taken periodically to evaluate the effects of storage conditions on color, purity, invert sugar content and other parameters. It was concluded that sugar of high quality stores better compared to conventional sugar. However, even VHP sugar can double its color during long-term storage. Sampling near the surface of the sugar pile (up to 1.5 m inside the pile) is not representative of the bulk of sugar. It has been found that sugar temperature follows the ambient trend as deep as 3 m inside the pile. Sugar within 1.5 m of the surface that was not subjected to temperature increase stored well compared to sugar in the core of the pile. It is unclear what conditions trigger color increase in storage. Changes in temperature profiles of raw sugar during storage in commercial warehouses indicate that some exothermic reactions take place in the core of the piles that result in color increase and reduction of sucrose content. The reactions take place even when the initial sugar water content and temperature meet the requirements accepted for safe storage (safety factor below 0.25 and temperature below 30 °C). Lower sugar pH value may be one of the reasons that make sugar less stable in storage. Options of cooling sugar before or during the storage will be considered in future research.