Earth pressure on cantilever walls at design retained heights

There are many methods for the analysis and design of embedded cantilever retaining walls. They involve various different simplifications of the pressure distribution to allow calculation of the limiting equilibrium retained height and the bending moment when the retained height is less than the limiting equilibrium value, i.e. the serviceability case. Recently, a new method for determining the serviceability earth pressure and bending moment has been proposed. This method makes an assumption defining the point of zero net pressure. This assumption implies that the passive pressure is not fully mobilised immediately below the excavation level. The finite element analyses presented in this paper examine the net pressure distribution on walls in which the retained height is less, than the limiting equilibrium value. The study shows that for all practical walls, the earth pressure distributions on the front and back of the wall are at their limit values, Kp and K-a respectively, when the lumped factor of safety F-r is less than or equal to2.0. A rectilinear net pressure distribution is proposed that is intuitively logical. It produces good predictions of the complete bending moment diagram for walls in the service configuration and the proposed method gives results that have excellent agreement with centrifuge model tests. The study shows that the method for determining the serviceability bending moment suggested by Padfield and Mair(1) in the CIRIA Report 104 gives excellent predictions of the maximum bending moment in practical cantilever walls. It provides the missing data that have been needed to verify and justify the CIRIA 104 method.

Dynamic earth pressures against a retaining wall caused by Rayleigh waves

An approximate procedure for studying harmonic soil-structure interaction problems is presented. The presence of Rayleigh waves is considered and the resulting governing equations of the dynamic soil-structure system are solved in the time domain. With this method the transient and steady states of a vibratory motion and also the nonlinear behaviour of the soil can be studied. As an example, the dynamic earth pressure against a rigid retaining wall is investigated. The loads are assumed to be harmonic Rayleigh waves with both static and dynamic surface surcharges. The dependence of the results on the excitation frequency is shown.

Identification of Practices, Design, Construction, and Repair Using Trenchless Technology, TR-570, 2010

Trenchless technologies are methods used for the construction and rehabilitation of underground utility pipes. These methods are growing increasingly popular due to their versatility and their potential to lower project costs. However, the use of trenchless technologies in Iowa and their effects on surrounding soil and nearby structures has not been adequately documented. Surveys of and interviews with professionals working in trenchless-related industries in Iowa were conducted, and the results were analyzed and compared to survey results from the United States as a whole. The surveys focused on method familiarity, pavement distress observed, reliability of trenchless methods, and future improvements. Results indicate that the frequency of pavement distress or other trenchless-related issues are an ongoing problem in the industry. Inadequate soil information and quality control/quality assurance (QC/QA) are partially to blame. Fieldwork involving the observation of trenchless construction projects was undertaken with the purpose of documenting current practices and applications of trenchless technology in the United States and Iowa. Field tests were performed in which push-in pressure cells were used to measure the soil stresses induced by trenchless construction methods. A program of laboratory soil testing was carried out in conjunction with the field testing. Soil testing showed that the installations were made in sandy clay or well-graded sand with silt and gravel. Pipes were installed primarily using horizontal directional drilling with pipe diameters from 3 to 12 inches. Pressure cell monitoring was conducted during the following construction phases: pilot bore, pre-reaming, and combined pipe pulling and reaming. The greatest increase in lateral earth pressure was 5.6 psi and was detected 2.1 feet from the centerline of the bore during a pilot hole operation in sandy lean clay. Measurements from 1.0 to 2.5 psi were common. Comparisons were made between field measurements and analytical and finite element calculation methods.

Effects of Implements of Husbandry (Farm Equipment) on Pavement Performance, TR-563, 2012

The effects of farm equipment on the structural behavior of flexible and rigid pavements were investigated in this study. The project quantified the difference in pavement behavior caused by heavy farm equipment as compared to a typical 5-axle, 80 kip semi-truck. This research was conducted on full scale pavement test sections designed and constructed at the Minnesota Road Research facility (MnROAD). The testing was conducted in the spring and fall seasons to capture responses when the pavement is at its weakest state and when agricultural vehicles operate at a higher frequency, respectively. The flexible pavement sections were heavily instrumented with strain gauges and earth pressure cells to measure essential pavement responses under heavy agricultural vehicles, whereas the rigid pavement sections were instrumented with strain gauges and linear variable differential transducers (LVDTs). The full scale testing data collected in this study were used to validate and calibrate analytical models used to predict relative damage to pavements. The developed procedure uses various inputs (including axle weight, tire footprint, pavement structure, material characteristics, and climatic information) to determine the critical pavement responses (strains and deflections). An analysis was performed to determine the damage caused by various types of vehicles to the roadway when there is a need to move large amounts agricultural product.

Modeling, Estimation, and Control of Robot-Soil Interactions

This thesis presents the development of hardware, theory, and experimental methods to enable a robotic manipulator arm to interact with soils and estimate soil properties from interaction forces. Unlike the majority of robotic systems interacting with soil, our objective is parameter estimation, not excavation. To this end, we design our manipulator with a flat plate for easy modeling of interactions. By using a flat plate, we take advantage of the wealth of research on the similar problem of earth pressure on retaining walls. There are a number of existing earth pressure models. These models typically provide estimates of force which are in uncertain relation to the true force. A recent technique, known as numerical limit analysis, provides upper and lower bounds on the true force. Predictions from the numerical limit analysis technique are shown to be in good agreement with other accepted models. Experimental methods for plate insertion, soil-tool interface friction estimation, and control of applied forces on the soil are presented. In addition, a novel graphical technique for inverting the soil models is developed, which is an improvement over standard nonlinear optimization. This graphical technique utilizes the uncertainties associated with each set of force measurements to obtain all possible parameters which could have produced the measured forces. The system is tested on three cohesionless soils, two in a loose state and one in a loose and dense state. The results are compared with friction angles obtained from direct shear tests. The results highlight a number of key points. Common assumptions are made in soil modeling. Most notably, the Mohr-Coulomb failure law and perfectly plastic behavior. In the direct shear tests, a marked dependence of friction angle on the normal stress at low stresses is found. This has ramifications for any study of friction done at low stresses. In addition, gradual failures are often observed for vertical tools and tools inclined away from the direction of motion. After accounting for the change in friction angle at low stresses, the results show good agreement with the direct shear values.

Parâmetros geotécnicos e previsão da capacidade de carga de estacas apiloadas em solo tropical arenoso obtidos com o Pressiômetro Ménard

This paper presents and discusses Ménard Pressuremeter test results used to predict bearing capacity of pounded piles installed in a tropical sandy soil. Fifteen pre-bored pressuremeter tests were carried out at the Experimental Research Site from Unesp - Bauru up to 15 m depth, one test per meter. Several laboratory and in situ tests were carried out in this research site as well as load tests on plates and on piles. Pressuremeter test results were firstly analyzed to determine geotechnical soil parameters based on empirical methods, emphasizing the estimative of the earth pressure coefficient at rest (K0). After that, bearing capacity prediction of pounded piles with 4 m, 7 m and 10 m were made and compared with test results from instrumented load tests. Pressuremeter test results allowed a very good estimative of bearing capacity for the pile with 4 m length and underestimated in 25,7% and 20,0% the bearing capacity for the pile with 7 and 10 m length, respectively. The back analysis of the test results suggests that the appropriate value for the bearing capacity factor for the tested soil-pile system on this soil is equal to 2.

Respuesta estática y sísmica de gasoductos

El objetivo de esta tesis es el estudio de la respuesta estructural de los gasoductos sometidas a solicitaciones estáticas y dinámicas, enfocando prioritariamente en la respuesta sísmica. Los gasoductos, como las tuberías en general, se utilizan principalmente para la transportación de fluidos, como agua, gas o petróleo, de ahí la importancia de que el diseño y la estructura se realicen adecuadamente. La tubería debe ser capaz de soportar tanto los efectos de cargas estáticas como las debidas al peso propio o de la presión de la tierra, así como los diferentes tipos de cargas dinámicas ocurridas durante un evento sísmico, como los debidos a las ondas o el desplazamiento de fallas. En la primera parte de la tesis se describen aspectos generales de la tubería y su uso, y se da una breve historia de uso en la industria y las redes de abastecimiento urbano. Aparte de otros aspectos, se discuten las ventajas y desventajas de los diferentes materiales de las tuberías. En la segunda parte de la tesis se desarrollan las ecuaciones de equilibrio de una sección transversal de la tubería bajo cargas estáticas, tales como la presión interna, peso propio, presión de la tierra y las cargas externas. Un número de diferentes combinaciones de carga es analizado por medio de programas codificados como Matlab, los cuales se han desarrollado específicamente para este propósito. Los resultados se comparan con los obtenidos en Ansys utilizando un código de elementos finitos. En la tercera parte se presenta la respuesta dinámica de las tuberías, que abarca los efectos de las ondas y los desplazamientos de fallas. Se presentan las características relevantes del suelo como las velocidades de ondas, así como los métodos para estimar el desplazamiento máximo de las fallas. Un estudio paramétrico se emplea para ilustrar la influencia de estos parámetros en la respuesta estructural de la tubería. Con este fin se han utilizado dos métodos, el Pseudoestático y el Simplificado. En la última parte de la tesis son desarrollados los modelos de elementos finitos que permiten simular adecuadamente el comportamiento no lineal del suelo y la tubería. Los resultados se comparan con los obtenidos por un método simplificado utilizado con frecuencia que fue propuesto por Kennedy en 1977. Estudios paramétricos se presentan con el fin de examinar la validez de las hipótesis del método de Kennedy. La tesis concluye con recomendaciones que indican en qué casos los resultados obtenidos por el método de Kennedy son conservadores y cuando es preferible utilizar modelos de elementos finitos para estimar la respuesta de las tuberías durante los terremotos. ABSTRACT The subject of this thesis is the study of the structural response of pipelines subjected to static and dynamic loads with special attention to seismic design loads. Pipelines, as pipes in general, are used primarily for the transportation of fluids like water, gas or oil, hence the importance of an adequate design and structural behaviour. The pipe must be able to withstand both the effects of static loads like those due to self-weight or earth pressure as well as the different types of dynamic loads during a seismic event like those due to wave passing or fault displacements. In the first part of the thesis general aspects of pipelines and their use are described and a brief history of their usage in industry and for urban supply networks is given. Apart from other aspects, the advantages and disadvantages of different pipe materials are discussed. In the second part of the thesis the equilibrium equations of a transverse section of the pipe under static loads such as internal pressure, self-weight, earth pressure and external loads are developed. A number of different load combinations is analysed by means of programs coded in Matlab that have been specifically developed for this purpose. The results are compared to those obtained with the commercial Finite Element code Ansys. In the third part the dynamic response of pipelines during earthquakes is presented, covering the effects of passing waves and fault displacements. Relevant soil characteristics like wave propagation velocities as well as methods to estimate the maximum fault displacements are presented. A parametric study is employed to illustrate the influences of these parameters on the structural response of the pipe. To this end two methods have been used, the Pseudostatic and the Simplified method. In the last part of the thesis Finite Element models are developed which allow to adequately simulate the nonlinear behaviour of the soil and the pipe. The results are compared to those obtained by a frequently used simplified method which was proposed by Kennedy in 1977. Parametric studies are presented in order to examine the validity of the hypotheses Kennedys’ method is based on. The thesis concludes with recommendations indicating in which cases the results obtained by Kennedy’s method are conservative and when it is preferable to use Finite Element models to estimate the response of pipelines during earthquakes.

The effects of restraining boundaries on the passive resistance of sand; results of a series of tests with a medium-scale testing apparatus. Report submitted to the Office of Naval Research, Dept. of the Navy,

"Project No. Nr-081-117. Contract No. Nonr-100 9(00)"

Design manual for permanent ground anchor walls /

"September 1998."

Embankment stability analysis. Pere Marquette Railroad (main line)-Detroit Industrial Expressway crossing. Project: X-7 of 82-22-10.

Mode of access: Internet.

Poussée des terres ...

Mode of access: Internet.

Dimensionamento de uma estrutura de contenção de terras flexível com vários níveis de apoio

O presente trabalho, no âmbito de projeto final de curso de metrado em Engenharia da Construção, teve como objetivo o estudo do comportamento de estruturas de suporte de terras flexíveis multi-apoiadas (com diferentes tipos de apoio) para dois tipos solos homogéneos. Recorreu-se às teorias clássicas, como a de Rankine, desenvolvidas para estruturas de suporte de terras rígidas. Às teorias semi-empíricas de Terzaghi & Peck que culminaram nos diagramas de Terzaghi & Peck. Apesar de os digramas de Terzaghi & Peck serem diagramas de pressões de terras a usar em estruturas de suporte de terras flexíveis, apresentam algumas limitações importantes, como a sua aplicação apenas em solos heterogéneos, com presença ou não de níveis freáticos, e sem fornecer distribuição das pressões de terras na zona passiva (zona enterrada). Como na atualidade os modelos de elementos finitos permitem simular de modo muito mais rigoroso os problemas da engenharia. O presente trabalho esteve focado em analisar um caso prático em diferentes solos e com diferentes tipos de apoios. Será estudado mediante os métodos analíticos usando as teorias clássicas e posteriormente métodos numéricos (com diferentes programas de cálculo). Finalmente serão comparados os resultados obtidos mediante os diferentes métodos usados. As estruturas foram inicialmente pré-dimensionadas usando os métodos clássicos. Assim foram usados os diagramas de pressões de terras de Terzaghi & Peck para a zona ativa (zona em escavação) e a teoria de Rankine para conhecer as pressões de terras na zona enterrada da cortina (parede moldada) e recorrendo ao software Ftool para a obtenção dos parâmetros de dimensionamento de estruturas de suporte de terras objeto de estudo. Posteriormente utilizaram-se os programas de cálculo automático CYPE 2015 k, e o programa de cálculo de elementos finitos PLAXIS Introductory 2010. Estes programas permitem simular o faseamento construtivo do muro. Para estudar a influência de algúns parâmetros no comportamento da Resumo IV cortina o estudo foi realizado com dois solos distintos, um solo argiloso mole e um solo arenoso denso. Assim como para dois tipos de apoios distintos, ancoragens ativas e escoras passivas. Foram analisados diferentes parâmetros na estrutura de suporte; pressões horizontais das terras, deslocamentos horizontais, esforço axial, transverso e momento fletor.

Impact of Earth radiation pressure on LAGEOS orbits and on the global scale

The indirect solar radiation pressure caused by reflected or re-emitted radiation by the Earth’s surface is an important non-gravitational force perturbing the orbits of geodetic satellites (Rubincam and Weiss, 1986; Martin and Rubincam, 1996). In the case of LAGEOS this acceleration is of the order of 15% of the direct solar radiation pressure. Therefore, Earth radiation pressure has a non-negligible impact not only on LAGEOS orbits, but also on the SLR-derived terrestrial reference frame. We investigate the impact of the Earth radiation pressure on LAGEOS orbits and on the SLR-derived parameters. Earth radiation pressure has a remarkable impact on the semi-major axes of the LAGEOS satellites, causing a systematic reduction of 1.5 mm. The infrared Earth radiation causes a reduction of about 1.0 mm and the Earth’s reflectivity of 0.5 mm of the LAGEOS’ semi-major axes. The global scale defined by the SLR network is changed by 0.07 ppb, when applying Earth radiation pressure. The resulting station heights differ by 0.5-0.6 mm in the solution with and without Earth radiation pressure. However, when range biases are estimated, the height differences are absorbed by the range biases, and thus, the station heights are not shifted.