Showing papers on "Lateral earth pressure published in 1978"

New Aspects of Soil Fracturing in Clay

Abstract: A theoretical analysis using cavity expansion theory suggests that soil fracturing can occur within the plastic zone during expansion of a cavity in clay. Results from pore pressure measurements during pile driving and hydraulic fracturing tests support these theoretical conclusions. Practical consequences of soil fracturing are considered with respect to pile driving in clay, the efficiency of driven sand drains as well as field permeability tests. An analysis of the hydraulic fracturing tests for determination of in-situ stresses indicates that, in almost all cohesive soils, fracturing is likely to occur along vertical planes in both normally and overconsolidated clays.

Field Experiment of Reinforced Earth Wall

Abstract: A field test conducted at the U.S. Army Engineer Waterways Experiment Station indicated that the reinforced earth concept provides another alternative for constructing earth structures which may prove to be more economical when compared with conventional methods under certain conditions. Based on instrumentation measurements collected during construction and during loading of a retaining wall backfilled with sand and reinforced with galvanized steel ties, it appears that the Rankine earth pressure theory provides a good approximation for the measured lateral pressure when the wall is carrying little or no surcharge load. Prior to failure under a substantial surcharge loading, the measured lateral earth pressure was maximum at the middle third of the wall and varied from 1.0 to 1.2 times the Rankine active earth pressure. The curve connecting the points where maximum tensile stress occurred in the reinforcing ties did not coincide with the theoretical Rankine failure surface.

Closure of "Lateral Earth Pressure at Rest in Soft Clay"

Abstract: The lateral earth pressure at rest in a soft cohesive soil as determined by five different methods at Backebol, Sweden is compared and analyzed. The agreement between the results using a thin earth pressure cell and a self-boring pressuremeter was satisfactory. It was found that the results from conventional pressuremeter tests were difficult to interpret. This method as well as the hydraulic fracturing method seems to overestimate the lateral earth pressure at rest for very soft clays. The lateral earth pressure as determined by a total stress cell (Camkometer) installed in an excavated borehole was low and erratic.

End restraint effects on cyclic triaxial strength of sand

Abstract: Cyclic triaxial tests were performed on various soils at different densities and different consolidation pressures, using regular and lubricated ends to explore the possible effect of end restraint...

Soil compressibility as measured in the oedometer

Abstract: The evaluation of oedometer tests and the calculation of settlement can be based on the linear plot of the constrined modulaus D with consolidation pressure p. This plot has a U shape and presents the following advantages: it reveals the minumum value of D and the pressure where it occurs; it shows the range of pressures where the soil is strain softening; it illustrates one of the causes of the variation of cv with p; it is applicable to a wide range of soil types. The D against p model is compared with other current models of the variation of compressibility with pressure. It is in agreement with the widely accepted e against log p model but inconsitent with the exponential and linear models. The value of D which is needed for a settlement calculation can be estimated roughly from a settlement calculation can be estimated roughly from the natural dry density or, in the case of saturated soil, from the natural water content. The value of D which enters this calculation is the specific constrained modulus...

Prediction of Undrained Behavior of Sand

Abstract: An elasto-plastic stress-strain theory for cohensionless soil with curved yield surfaces is used for prediction of soil and pore pressure behavior in undrained triaxial tests on saturated sand specimens Prediction of pore pressures is performed using the condition that no volume change occurs in undrained tests for any increment in load The soil stress-strain relations are calculated from the effective stress-paths deduced from the applied deviator stress, the cell pressure, and the predicted pore pressure Effects of back pressure and cavitation of pore water can be calculated from the theory Predictions of stress-strain relations, pore pressure variation, expansion after cavitation, effective stress-paths, and critical confining pressures compare favorably with experimental results for loose and dense Sacramento River Sand The importance of employing curved failure surfaces for realistic prediction of undrained behavior is emphasized, and it is shown that most soils exhibit curved failure surfaces

Soil mechanics, second edition

Abstract: The second edition of the book is designed to provide a concise and logical explanation of the fundamental principles of soil mechanics. It includes the semi-empirical approach to practical problems in soil engineering. A comprehensive range of worked examples is included to illustrate the application of fundamental principles in practical situations. The subject is discussed in the following chapters: (1) basic characteristics of soils, (2) seepage, (3) effective stress, (4) shear strength, (5) lateral earth pressure, (6) stresses and displacements, (7) consolidation theory, (8) bearing capacity, (9) stability of slopes, and, (10) ground investigation. /TRRL/

Behavior of stress cells in soil

Abstract: The design, construction and analysis of a soil stress cell for measuring earth pressures is described. The cell is build for use under dry, controlled, laboratory conditions, where environmental effects are minimized. Emphasis is placed on the understanding of stress cell-soil interaction, rather than the details of cell construction. Two completely separable phenomena were dealt with in describing the effects of lateral stresses on strell cell measurements. First, cross-sensitivity of cells due to direct compression of strain gauges is discussed and a design technique is proposed to eliminate the problem. Second, the fact that lateral stresses cause normal stresses on the cell as a result of the presence of the cell is discussed. Poisson's ratio for the soil is found to be the key parameter in quantifying this effect. A model is proposed to correct stress cell measurements for lateral stress rotation. Experimental laboratory data and the Finite Element Method were used for development of the model. /Author/

Modelling reinforced earth

Abstract: Centrifugal modelling offers an opportunity to witness collapses of soil, structured or composite models in circumstances which are not unlike those of full-scale constructions. It is hoped that the new form can be safely analyzed in terms of existing mechanical principles. If so, then these principles will allow the refinement of the new technique, allow its extension more quickly into improved areas, and allow a more rigorous analysis of safety that can be gained by having not yet made an error in practice. The models used were proportioned and oriented so as to reduce those errors in stress which are due to the non-uniformity of the acceleration field to below 10% in the critical region. The capacities of the models were specifically chosen so that a number of tension failures and slippage failures could be observed to disrupt the reinforcement and cause collapse. The dry sand used in all the models was a well-graded coarse to fine glacial sand. The conclusions include among others, that centrifugal models confirm the usefulness of the anchor concept of reinforced earth. An actual earth pressure coefficient measured on loose soil would have safely underpredicted the failure of anchors in tension by a factor of 2.2 to 3.3 and in slippage by a factor of 1.6 to 2.2. Since the friction capacity of an anchor may be made larger without using a greater weight of reinforcement, simply by spreading the same material wider and thinner, it may be economical to employ factors of safety against slippage which are very much larger than two. Future work should be devoted to a further understanding of the stresses in reinforced earth walls, the effects of surface forces and poor foundations, and the feasibility of clay fills.

Design aspects of reinforced earth construction

Abstract: This article discusses how a reinforced earth wall fits in with other components of a road cross-section--the road pavement, drainage, services, safety fences, and parapets. An example of a reinforced earth wall supporting a motorway embankment is considered. The cost of a typical 6 m high wall is made up as follows: Selected fill--30%, reinforcing elements--30%, connections--5%, cladding units--35%. Most of the reinforced earth retaining walls that have been built throughout the world have used metallic strip reinforcing elements. An example of the typical properties of four metallic reinforcing elements are presented. Also included is a comparison of the percentage extension at working load, the relative cost of supply per unit force, and the relative weight per unit force for these four materials. It is noted that one of the advantages of metallic reinforcing elements is the ease with which they can be connected to the cladding units. One problem designers have is in deciding what properties to assume for the fill in and behind the wall. It has been shown than an equivalent cohesionless fill with an angle of internal friction of 30 degrees and density equal to 19K N/M cubed would give a conservative prediction of earth pressures for most fills used in this country provided the wall is not greater than 12 m high.

Soil stress measurement experiences

Abstract: Equipment and techniques that have been used for measuring soil pressures on underlying or retaining structures are described. Typical data are presented and considered that show a range of soil pressure transfer or concentration effects, depending on the design of special soil buffler zones or projecting conditions of the rigid structures. Equipment and techniques of measurement are also described for measurement of the principal soil stresses within an embankment mass. Principal soil stress data are presented and examined for two major earthfill dams, which show evidence of arching effects between the zones of different compressibility. /Author/

At-rest lateral earth pressure coefficient of a granular medium

Abstract: 1. The at-rest pressure in a granular medium depends on the angle of internal friction, history of occurence of the stressed state, and boundary conditions.

Behaviour of a diaphragm wall

Abstract: THIS PAPER WAS PRESENTED AT SESSION 3 OF THE 9TH INTERNATIONAL CONGRESS OF SOIL MECHANICS AND FOUNDATION ENGINEERING, TOKYO, JULY 1977. IT PRESENTS THE RESULTS OF MEASUREMENTS MADE ON A 20-M HIGH REINFORCED CONCRETE SLURRY TRENCH WALL WHICH FORMED THE RETAINING WALL OF AN EXCAVATION 21 M DEEP DUG IN FORMATIONS TYPICAL OF THE PARIS REGION. THE WALL WAS ANCHORED BY MEANS OF 4 ROWS OF BORED PRESTRESSED TIE RODS. DURING EARTHWORKS THE ACTIVE EARTH PRESSURE ON THE WALL WAS MEASURED, TOGETHER WITH CONCRETE DEFORMATIONS, STRESSES IN THE TIE RODS AND DISPLACEMENTS OF THE WALL. THE MOST CHARACTERISTIC OF THESE MEASUREMENTS ARE PRESENTED AND COMPARED TO VALUES OBTAINED WITH FINITE ELEMENT CALCULATIONS AND ELASTIC BEAM CALCULATIONS TAKING INTO ACCOUNT THE ELASTOPLASTIC REACTION OF THE SOIL. FOR THE COVERING ABSTRACT OF THE CONFERENCE, SEE IRRD ABSTRACT NO 107555.

Earth Pressures on Conduits and Retaining Walls.

Abstract: : The objective of this investigation was to improve current design procedures for predicting earth pressures on rigid (concrete) conduits and retaining walls of the type frequently built by the U.S. Army Corps of Engineers. A comprehensive literature review was made to determine the generally accepted design methods (in addition to those of the Corps of Engineers) for predicting earth pressures on rigid conduits and retaining walls. Finite-element computer studies were performed to investigate the nature of earth pressures on buried conduits. Analytical comparisons were made of the many theories available for predicting earth pressures on retaining walls. Several suggested improvements to present Corps of Engineers design methods resulted from this study. The recommended procedures were compared with earth pressure data from several Corps of Engineer projects. In general, the suggested changes resulted in more accurate predictions of earth pressures on rigid conduits and retaining walls than are calculated by the present methods. This investigation has indicated several areas of inadequate present knowledge that could warrant further field and/or analytical study.

CALCULATION OF SEISMIC PASSIVE EARTH PRESSURE IN THE CASE OF ψu=0, Cu 0 FOR THE SOILS

Abstract: 力,斜 面安定の広範 囲にわたって示 した.い ずれ も土の つ り合 い条件 と強度条件 を満足 させてい る.し か しなが ら,土 圧に関 して静的 の場 で,地 表面が水 平な場 合のみ であって,こ れは後述す るよ うに,特 性線 に沿 って積 分 が可能であ って簡単 に解 が得 られ る.地 震 時におけ る慣 性力が作用する場合 は,一 般 に地表面が水 平な静的の土 圧 とは異な って,特 性線 に沿 って,応 力の積 分が不 可能 である.そ れゆえ,電 子計算機 を使用 して差分式 の解 を 求 めなければな らない。 筆者の一人は以前c=0,g≠0の 場合の壁面に作 用す る地震時受働土圧 を求 めた2).ま たc≠0,φ≠0の 場合 の壁面 に作用する地震時受働土圧 も求 めた3).こ れ らは いずれ も土のつ り合 い条件 と強度条件 を満足 させるすべ り面 に沿 って壁面土圧 を求 めている.こ の後者 の手 法, す なわち,土 圧 を求 める漸化式 において,φ=0と して, ここに示す φu=0,cu≠0の 土圧 を求める ことは理論上 できない. 筆者 らの研究 の内容 を示す と次の ようにな る.筆 者 ら は壁面 の傾角 と,地 盤面 の傾角 また土 の粘着 力に起 因す る壁面 に発揮 され るせ ん断応 力の大 きさ,土 体に作 用す る地震力 の 大 きさを 種 々変化 させて 受働 土圧 を算 定 し た.こ れ ら一連 の算定 において特異点 の解 を用いる場合 と不連続線の 解 を用 いる場合 が あ った.不 連続解 は 前 報3)と 同 じく,原 点近傍 の近似値 を求 め,第4境 界値 問 題の解法 を適用 して,不 連続線 と壁面土圧 を求 める方 法 をとった.こ の ようにして求 めた結果 をLeeの 方法4)に よる結果 と比較 した.ま た,筆 者 らは上記不連続解 で得 た壁面土圧 を特異点の解 を強行 して求 めた結果 と比較 し た.こ の ような比較は特異点の解 によった ほ うが土圧 の 算定が容易であ るためで ある. 一連 の算定で得 られた土圧分布は一般 に曲線 の分布 と