Lateral Soil Displacement Research Articles

Modeling Landscape Evolution Due to Tillage: Model Development

Tillage erosion has been identified as an important contributor to the modification of agricultural landscapes. A two-dimensional, grid-based model has been developed to compute soil redistribution and morphological changes of complex landscapes due to tillage operations. Soil movement along and perpendicular to the directions of tractor movement are computed as a function of local slope gradients and of characteristics of the tillage implement. A control volume approach is employed to determine terrain elevation changes after each tillage pass. The model explicitly considers the presence of internal and external field boundaries, simulating their influence on the development of erosion and deposition patterns. GIS layers are used to provide terrain elevation data, actual tillage directions, field borders, and the location of other features, such as vegetated strips, trees, or fences. The model was verified against an analytical solution for the development of bench terraces due to tillage between vegetated strips. The model's capability of considering variable tillage directions was tested with a simulation of tillage erosion over a synthetic, undulating surface and was used to investigate how an implement's forward and lateral soil displacement characteristics influence erosion patterns as a function of tillage direction relative to slope. The model's stability, computational efficiency, and ability to simulate fields with complex boundaries and varying tillage directions allow its use as a practical tool within a comprehensive conservation planning system.

Behavior of Circular Footings Resting on Confined Granular Soil

This paper presents the results of laboratory model tests on the influence of soil confinement on the behavior of a model footing resting on granular soil. Confining cylinders with different heights and diameters were used to confine the sand. The ultimate bearing load of a circular footing supported on a three-dimensional confined sand bed was studied. The studied parameters include the cell height, cell diameter, the depth to the top of the cell, and the embedded depth of footing. Initially, the response of a nonconfined case was determined and then compared with that of confined soil. The results were then analyzed to study the effect of each parameter. The results indicate that the bearing load capacity of circular footing can be appreciably increased by soil confinement. It was concluded that such reinforcement resists lateral displacement of soil underneath the footing leading to a significant improvement in the response of the footing. For small cell diameters, the cell–soil footing behaves as one ...

Response of 0.6m Cast-in-Steel-Shell Pile in Liquefied Soil under Lateral Loading

This paper presents results from a full-scale lateral load test on a 0.6 m cast-in-steel-shell (CISS) pile in sand liquefied by controlled blasting. Lateral loads were applied by a hydraulic actuator to simulate seismic inertial forces. The CISS pile was instrumented to provide the data necessary for back calculating lateral soil resistance and displacement. Details of the pile instrumentation and testing procedure are described. The back-calculated soil resistance and displacement are presented as p–y curves and compared to static sand p–y curves. Results from three simplified analyses are presented, where liquefied soil resistance was accounted for by modifying standard static p–y curves, and compared to measured test results. Limitations of the simplified methods are discussed. Test results show the blast induced liquefied sand did not provide resistance to lateral pile movement at displacements up to 50 mm . At displacements of sufficient magnitude, a phase transformation in the sand occurred resultin...

Modelling vertical and lateral weed seed movements during mouldboard ploughing with a skim-coulter

The vertical distribution of weed seeds in soil is crucial because seedling emergence varies with seed depth, whereas lateral soil displacement during mouldboard ploughing contributes to weed dispersal within the tilled field. In order to model vertical and lateral seed displacements during ploughing, an existing model describing soil particle movements for different ploughing characteristics (depth and width) and soil structures was adapted to integrate the effect of a skim-coulter. This model was tested in two field trials, in Northern France, using coloured plastic beads to imitate weed seeds. The trial in Dijon was set up on an eutric cambisol and comprised both compacted and uncompacted soil. The second trial was set up at Grignon, on an orthic luvisol which was left uncompacted before ploughing. The model correctly simulated the lateral displacement (LD) and the final vertical co-ordinate of the beads as a function of their initial location, soil structure before ploughing and ploughing parameters (ploughing depth and width; skim-coulter depth and width). The model was then used to calculate seed transfer matrixes describing vertical seed movements between seed bank layers and vertical seed distributions for different conditions and plough modes. The results were consistent with those of Cousens and Moss [Weed Res. 30 (1990) 61–70]. Simulations were performed to test the effect of different ploughing modes on the time changes in the vertical distribution of weed seeds and to show how the model can be used to manage weed seed concentration in the top layer by soil tillage. Furthermore, simulations showed that the vertical distribution of the seed bank could be extremely variable, depending on plough characteristics, soil structure or initial seed distribution. Although further studies are needed on the long-term seed movements under the influence of secondary tillage and climate, this model can be useful for evaluating different tillage modes on seed dispersal within the ploughed layers.

Deformation processes below a plate sinkage test on sandy loam soil: experimental approach

Mathematical models to predict the mode and extent of deformation occurring below sinkage plates are presented in the first part of this paper which encompasses the theoretical approach to the subject. These models are based on previous work by Earl (Earl R. Assessment of the behaviour of field soils during compression. Journal of Agricultural Engineering Research 1997;68:147–57)who developed a procedure to predict the likely mode of deformation using confined compression tests carried out alongside plate sinkage tests. This work suggested that soil behaviour, during increasing compression under a sinkage plate, is governed by three processes; (i) compaction below the plate with constant lateral stress, (ii) compaction with increasing lateral stress, and (iii) displacement and compaction of soil laterally. The aim of this second part to the paper is to observe soil deformation processes occurring below a circular sinkage plate to examine (i) whether the three phases of deformation referred to above occur in practice, and (ii) the accuracy of the models for predicting the soil deformation processes that occur. Tests were carried out on sandy loam soil under controlled conditions in a soil bin. Observations of deformation processes, recorded using long-exposure photography, revealed that during the initial stages of sinkage (a few millimetres), the corresponding disturbance of soil below the plate extended disproportionately further and was cylindrical in form. As sinkage progressed, the deformation process went through a transitional stage before reaching the more widely recognised form of the development of an inverted cone of compacted soil directly below the plate which moved with the plate causing lateral soil movement and compaction. Predictions for a medium density sandy loam were found to be in broad agreement with soil behaviour under a semi-circular sinkage plate observed behind a sheet of tempered glass under controlled conditions in a soil tank.

多翼部を有する小径鋼管杭工法の開発

This paper describes a bearing capacity formula for steel pipe pile with four helical wings. The pile can be possessed high bearing capacity because of being screwed in with lateral soil displacement. 21 vertical loading tests, in which a new measuring system for axial strain of the pile was devised, were performed to evaluate the bearing capacity of these piles in various fields. A convenient bearing capacity formula, which is considered as a sum of end bearing capacity of the pile tip and four wings, is proposed based on the test results.

Mathematical Principles in Prediction of Lateral Ground Displacement Induced by Seismic Liquefaction

ABSTRACT The present paper aims at developing a mathematical theory for prediction of the lateral soil displacement induced by seismic liquefaction. By using the knowledge obtained from shaking table tests together with the principle of the minimum potential energy at force equilibrium, the theory of maximum possible displacement was developed, and is described in detail. Boundary conditions as well as irregular topography were also considered using the principle of the minimum potential energy. Prediction of the increase of displacement with time was also attempted. This aim was achieved by using a scalar function of time, denoted by λ, that stands for the increase of displacement from zero towards the maximum possible one. An equation of motion in terms of λ was derived by using the theory of Lagrangean equation of motion together with the Hamiltonian principle. By combining the maximum possible displacement and λ, it is possible to predict the variation of displacement with time. The proposed method is characterized by its need for a limited number of input data.

Development of a Technique for Assessing the Behaviour of Soil under Load

Abstract The way in which soils behave during plate sinkage tests has a direct influence on the extent and severity of the resulting soil deformation. Photographic evidence of soil deformation behind a glass screen, obtained during this study, suggests that the mode of deformation, directly below the plate, is initially one of soil compaction owing to vertical soil displacement followed by a change to lateral compaction owing to lateral soil displacement. The transition from vertical to lateral deformation was found to be abrupt and occurred during the first few centimetres of sinkage. The point of change (compaction point), for a given situation, can be determined in terms of stress and sinkage by examining results from a confined compression test in conjunction with those from a plate sinkage test. Experiments were conducted in a soil bin on sandy loam soil and also in the field on sandy loam and clay soil, at a range of water contents and bulk densities, to observe the compactive nature of soil. Stress–sinkage relationships obtained from plate sinkage and confined compression tests were approximated by hyperbolas. These data were used to validate procedures proposed for predicting the compactive behaviour of soil under load. The initial gradient of the stress–sinkage curve (mps), and stress at the compaction point (σcp) are important parameters in determining the mode and extent of soil deformation under imposed loads. These were found to be related to, and could be predicted from, initial volumetric water content and initial dry bulk density. A strong relationship was found to exist betweenσcpandmpsfor combined data from sandy loam and clay field soils. This relationship could allow predictions ofσcpto be made from measures ofmps. This would provide simplification of assessment procedures in the field asmpscan be determined from a simple plate sinkage test, whereasσcprequires data from a confined compression test in addition to that from a plate sinkage test.

Analysis of Piles Subjected to Embankment Induced Lateral Soil Movements

Damage to piles supporting structures, bridge abutments, and utilities can occur as a result of the construction of nearby embankments. This is because the lateral displacements resulting from these construction activities can induce forces and moments in the piles. The resulting stresses can be significant particularly when soft soil deposits are present and the lateral soil displacements are large. This paper describes a simplified numerical procedure based on finite-element method for analyzing the response of single piles to lateral soil movements. The flexural bending of the pile is modeled by beam elements. The complex phenomenon of the pile-soil interaction is modeled by hyperbolic soil springs. A framework for determining the soil parameters for use in the analysis is summarized here. Comparisons are made between the observed behavior of full-scale tests and centrifuge model tests and those computed by the proposed numerical method. Based on parametric studies, empirical design solutions for pile foundation systems at the base of a sloped embankment are presented.

Field Behavior of Excavation Stabilized by Deep Soil Mixing

This paper describes the performance of a tiedback excavation with a soil mixed wall in Boston where underlying marine clay was stabilized by deep soil mixing (DSM) and jet grouting. Lateral and vertical soil displacements, soil strains, and tieback loads are evaluated. The interaction between the retained soil and a reinforced concrete box culvert, supported on drilled shafts, is described. Piezometer measurements behind the wall are summarized. They show pore-water pressures in marine clay substantially less than the hydrostatic pressures assumed in design.

Consolidation, Pre- and Post-Peak Shearing Responses from Internally Instrumented Biaxial Compression Device

Abstract An internally instrumented, servo-controlled biaxial compression device is described for evaluating shear band formation in soils. Internally measured vertical and lateral soil displacements as well as lateral deformations of a very low friction bottom sled allow one to observe the progressive development of shear bands in a specimen. Anisotropically consolidated specimens of relatively insensitive, soft Chicago glacial clay were sheared under undrained conditions. Differences in responses based on the internal and globally derived stress and strain quantities illustrate the uniformities which are attained during both consolidation and shear. Small, outward lateral displacements were observed during K0 consolidation, which was based on globally observed axial and volumetric strains; yet, observed Ko values were similar to those measured by other means. Observed lateral deformations during undrained shear and bottom sled movements showed the progressive development of a shear band in all tests. Nonuniformity of the deformations arose after attaining a peak shear stress. The globally observed strain-softening response was both constitutive and geometric in nature.

Full-displacement pressuremeter method for rigid piles under lateral loads and moments

The results of full-displacement pressuremeter tests in beds of sand, clay, and layered soil have been used to estimate the lateral soil pressures, ultimate capacity, and displacements of instrumented rigid model piles under eccentric and inclined loads. Comparisons of these estimates with observations on the piles under horizontal load and pure moment have been made and reasonable agreement is found. The analyses are also compared with some field case records. Key words: bearing capacity, clay, displacements, horizontal load, lateral pressure, layered soil, model test, moment, pile, pressuremeter, sand.

Lateral soil pressures and displacements of rigid piles in homogeneous soils under eccentric and inclined loads : Sastry, V V R N; Meyerhof, G G Can Geotech JV23, N3, Aug 1986, P281–P286

Lateral soil pressures and displacements of rigid piles in homogeneous soils under eccentric and inclined loads : Sastry, V V R N; Meyerhof, G G Can Geotech JV23, N3, Aug 1986, P281–P286

Influence of installation method on the behaviour of rigid piles in clay subjected to moment and horizontal load

The lateral soil pressure distribution, pile capacity, and displacements of instrumented single rigid bored piles subjected to pure moment and horizontal load have been investigated. The influence of method of pile installation on the above parameters is studied by comparing the behaviour of bored piles with that of jacked piles. It was concluded that the method of installation has practically no effect so far as the net lateral soil pressures and pile capacity are concerned, but the displacements may be up to three times larger for a bored pile than for a jacked pile under working loads. Key words: clay, horizontal load, installation, model test, moment, pile.

Lateral soil pressures and displacements of rigid piles in homogeneous soils under eccentric and inclined loads

The lateral soil pressures, tip load, and displacements of instrumented single rigid model piles in homogeneous loose sand and soft clay under vertical eccentric and central inclined loads have been investigated. A comparison of the test results with theoretical pressure distributions and displacements of the pile for the working load range has been made. Reasonable agreement has been found between the observed and predicted displacements and suggested nondimensional p–y curves. The analyses are also compared with the results of some field case records. Key words: displacements, clay, eccentric load, horizontal load, lateral soil pressure, instrumentation, model test, pile, sand.