Field Tests and Numerical Analyses of Subgrade Soil Reinforced with Grids of Stabilized Granular Columns

1996 ◽  
Vol 1534 (1) ◽  
pp. 72-79
Author(s):  
Evert C. Lawton ◽  
Anagha A. Mokashi ◽  
Nathaniel S. Fox
Keyword(s):  
Small Diameter ◽  
Field Tests ◽  
Reinforced Soil ◽  
Silty Sand ◽  
Silica Sand ◽  
Numerical Analyses ◽  
Triaxial Tests ◽  
Subgrade Soils ◽  
Subgrade Soil ◽  
Native Soil

Field tests and numerical analyses conducted to establish the feasibility of reinforcing soft, loose, or otherwise inadequate subgrade soils with a grid of small-diameter, stabilized, vertical granular columns to support traditional pavement systems are described. This technique may prove to be cost-effective if it is used to improve subgrade soils so that the sub-base or base courses can be reduced in thickness or eliminated. Field plate bearing tests were carried out on unreinforced cohesionless silty sand and on the same soil reinforced with vertical reinforcing columns constructed of four materials: crushed granitic gneiss, silica sand, cement-stabilized native soil, and cement-stabilized silica sand. The field tests indicated that the columns made of the two cement-stabilized materials substantially increased the subgrade modulus of the native soil. In contrast, the two unstabilized columnar reinforcing materials produced no substantial improvement in stiffness. The field tests were modeled by using an axisymmetric finite-element (FE) program and hyperbolic constitutive relationships for the native soil and the columnar reinforcing materials. Triaxial tests were performed on reconstituted specimens of the native soil and compacted specimens of cement-stabilized native soil to determine the stress–strain–strength parameters required for the FE analyses. The FE analyses modeled the plate bearing tests on the reinforced soil to a reasonable degree, indicating that the FE method used has the potential to simulate a complete pavement system (including a wearing surface) in which the subgrade soil is reinforced with columns of stabilized granular materials.

Using Repeated-Load Triaxial Tests to Evaluate Plastic Strain Potentials in Subgrade Soils

2005 ◽  
Vol 1913 (1) ◽  
pp. 86-98 ◽  
Author(s):  
Anand J. Puppala ◽  
Suppakit Chomtid ◽  
Venkat Bhadriraju
Keyword(s):  
Plastic Strain ◽  
Test Procedure ◽  
Soil Layer ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Plastic Strains ◽  
Plastic Deformations ◽  
Subgrade Soils ◽  
Repeated Load ◽  
Repeated Load Triaxial

The design and the analysis of flexible pavement systems depend on soil layer characterization, traffic loads, and number of passes. The current AASHTO design method for flexible pavements uses resilient characteristics of subsoils to characterize and determine the structural support of each layer and to design the thickness of the layers. This moduli property, however, does not fully account for the plastic strain or rutting potentials of subsoils, as in the cases in which silt and mixed soils undergo high plastic deformations but possess high resilient properties. A study was initiated to establish a test procedure to use a repeated load triaxial device to measure plastic strain potentials of subgrade soils. Laboratory-compacted soil specimens were subjected to a repeated deviatoric load, determined as a percentage of static deviatoric load at failure under un-consolidated undrained conditions. The plastic strains were monitored during 10,000 repeated load cycles, and the accumulated plastic deformations were determined. The test procedure and test results conducted on two types of soils, a coarse sand and silty sand, are presented. Effects of soil type, compaction moisture content, dry unit weight, confining pressure, and deviatoric stresses on the plastic strains were addressed.

Cyclic soil-root mechanical interaction

2021 ◽  
Author(s):  
Anthony Leung ◽  
Ali Akbar Karimzadeh ◽  
Zhaoyi Wu
Keyword(s):  
Triaxial Compression ◽  
Reinforced Soil ◽  
Plant Roots ◽  
Triaxial Tests ◽  
Uniaxial Tensile ◽  
Mechanical Interaction ◽  
Liquefaction Resistance ◽  
Cyclic Stress Ratio ◽  
Geotechnical Centrifuge ◽  
Wide Diameter

<p>Plant roots have been considered to be effective to reinforce shallow soil slopes under rainfall conditions. Recent evidence from geotechnical centrifuge modelling shows that plant roots could improve earthquake-induced slope stability and reduce slope crest settlement. However, the underlying fundamental mechanisms of soil-root mechanical interaction against seismic loading are unclear. Although there has been a large volume of studies focusing on root reinforcement, cyclic soil-root mechanical interaction has rarely been investigated. Moreover, whether plant roots could reduce the liquefaction potential of rooted soil. This presentation will present some new test data and evidence about (1) cyclic root biomechanical behaviour and (2) cyclic responses of root-reinforced soil. In part (1), results of cyclic uniaxial tensile tests on roots of a wide diameter range will be presented, including any root hardening or softening and change in the size of hysteresis loops under displacement-controlled loading condition. Special attention will be paid on any observation of cyclic-induced root mechanical fatigue. In part (2), results of a comprehensive set of monotonic and cyclic triaxial tests on rooted soil will be presented. The cyclic behaviour observed will be interpreted through the monotonic behaviour observed along both the triaxial compression and extension paths. Any change in soil failure mechanism from limited flow failure to cyclic mobility due to plant roots, and how/when this change occurs at different root volume and cyclic stress ratio, will be discussed in detailed. A new attempt to interpret the liquefaction resistance through an energy-based approach will be made to evaluate the energy dissipation mechanism in rooted soils.</p>

Comparative study of coral sand and silica sand in creep under general stress states

2017 ◽  
Vol 54 (11) ◽  
pp. 1601-1611 ◽  
Author(s):  
Yaru Lv ◽  
Feng Li ◽  
Yawen Liu ◽  
Pengxian Fan ◽  
Mingyang Wang
Keyword(s):  
Grain Size ◽  
Creep Behavior ◽  
Confining Pressure ◽  
Silica Sand ◽  
Triaxial Tests ◽  
Particle Crushing ◽  
Particle Rotation ◽  
General Stress ◽  
Coral Sand ◽  
Stress States

Coral sand has individual characteristics that differ from silica sand, such as creep behavior that is always attributed to particle crushing under high stress states. To understand the creep behavior of coral sand under general stress levels, three series of comparative triaxial tests relevant to the deviator stress, confining pressure, and relative density were performed on coral sand and silica sand creeping for more than 5 days. The volumetric, axial, and shear creeps of coral sand are considerably larger than those of silica sand, particularly under a relatively high confining pressure. The volumetric creep strain of coral sand was found to be contractive, but that of silica sand appeared dilative according to the creep time. This difference is not mainly governed by particle crushing in coral sand because the grain-size distribution prior to and after creep is similar. The grain skeletons were observed using a scanning electron microscope, finding that, independent of the grain size and shape, the coral grains include large amounts of cavities. The creep of coral sand under general stress conditions is mainly caused by particle interlocking, i.e., the angular regions of some particles interlock into the cavities of other particles due to particle rotation. This structuration is induced by breakage of asperities and voids during creep such as the local instability near cavities.

A Portable Slurry Wear Test for the Field

1989 ◽  
Vol 111 (3) ◽  
pp. 324-330 ◽  
Author(s):  
B. W. Madsen
Keyword(s):  
Laboratory Data ◽  
Electrochemical Corrosion ◽  
Field Tests ◽  
Wear Test ◽  
Field Testing ◽  
Silica Sand ◽  
Cast Irons ◽  
Wear And Corrosion ◽  
Lead Zinc ◽  
Processing Site

A new portable slurry wear test apparatus developed by the Bureau of Mines, U.S. Department of the Interior, makes it possible to gather materials wear and corrosion data at a mineral processing site. The portable wear cell is identical in design to a laboratory cell reported previously. It allows simultaneous evaluation of 16 specimens in a continuous flow of fresh slurry. Data obtained from selected metals and polymers showed high-chromium white cast irons to perform particularly well in tests with an aqueous lead-zinc sulfide ore slurry. However, ultra-high-molecular-weight polyethylene that exhibited superior wear resistance in comparable laboratory tests with an aqueous slurry of silica sand did not perform as well in field tests. Such results show how misleading it can be to use laboratory data to predict relative rates of wear in industrial slurries, even under nominally identical flow conditions. Field testing is therefore needed. In situ electrochemical corrosion measurements on a low-alloy steel showed that the field and laboratory slurries were similarly corrosive.

Modelling effects of pile diameter

2016 ◽  
Vol 53 (1) ◽  
pp. 173-178 ◽  
Author(s):  
W.D. Liam Finn ◽  
J. Dowling
Keyword(s):  
Small Diameter ◽  
Field Tests ◽  
Technical Note ◽  
American Petroleum Institute ◽  
Finite Element Program ◽  
Model Soil ◽  
Pile Diameter ◽  
Element Program ◽  
Load Tests ◽  
Diameter Effect

The most commonly used program for the analysis of piles under static lateral loading is LPILE. The program uses the nonlinear Winkler springs recommended by the American Petroleum Institute (API) to model soil–pile interaction. The p–y (load–displacement) curves were developed from field tests, with pile diameters in the range 0.324–0.67 m. When these p–y curves are used to analyze load tests on piles with larger diameters, the computed load–deflection curves underestimate the stiffnesses of the test piles. This effect is referred to as the pile diameter effect. In this technical note, a very different approach is presented to evaluate the pile diameter effect. Both LPILE and a continuum-based finite element program VERSAT-P3D were calibrated to closely simulate the results of two lateral load tests on small-diameter piles at two different sites. VERSAT-P3D modelled the volume of the pile and LPILE did not. Each program was used to develop p–y curves for increasingly larger pile diameters up to 2.0 m. An important finding for practice is that there was no pile diameter effect for displacements up to 60 mm. LPILE can be used with confidence in practice in this displacement range. Thereafter, the load–deflection curves from LPILE became softer and the pile diameter effect became evident.

scholarly journals Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests

2019 ◽  
Vol 9 (5) ◽  
pp. 900 ◽  
Author(s):  
Yixian Wang ◽  
Panpan Guo ◽  
Xian Li ◽  
Hang Lin ◽  
Yan Liu ◽  
...  
Keyword(s):  
Wheat Straw ◽  
Clayey Soil ◽  
Coupling Effect ◽  
Fiber Reinforcement ◽  
Reinforced Soil ◽  
Triaxial Tests ◽  
Fiber Reinforced ◽  
Microscopic Mechanism ◽  
Lime Stabilization ◽  
Stabilized Soil

The beneficial role of combining fiber reinforcement with lime stabilization in altering soil behavior has been established in the literature. However, the coupling effect of their combination still remains unclear in terms of its magnitude and microscopic mechanism, especially for natural fibers with special microstructures. The objective of this study was to investigate the coupling effect of wheat straw fiber reinforcement and lime stabilization on the mechanical behavior of Hefei clayey soil. To achieve this, an experimental program including unconsolidated–undrained (UU) triaxial tests and SEM analysis was implemented. Static compaction test samples were prepared on untreated soil, fiber-reinforced soil, lime-stabilized soil, and lime-stabilized/fiber-reinforced soil at optimum moisture content with determining of the maximum dry density of the untreated soil. The lime was added in three different contents of 2%, 4%, and 6%, and 13 mm long wheat straw fiber slices with a cross section one-quarter that of the intact ones were mixed in at 0.2%, 0.4%, and 0.6% by dry weight of soil. Analysis of the derived results indicated that the addition of a small amount of wheat straw fibers into lime-stabilized soil improved the intensity of the strain-softening behavior associated with mere lime stabilization. The observed evidence that the shear strength increase brought by a combination of 0.4% fiber reinforcement and 4% lime stabilization was smaller than the summation of the shear strength increases brought by their presence alone in a sample demonstrated a coupling effect between fiber reinforcement and lime stabilization. This coupling effect was also detected in the comparisons of the secant modulus and failure pattern between the combined treatment and the individual treatments. These manifestations of the coupling effect were explained by a microscopic mechanism wherein the fiber reinforcing effect was made more effective by the ways in which lime chemically stabilized the soil and lime stabilization development was quickened by the water channels passing through the surfaces and honeycomb pores of the wheat straw fibers.

Numerical Simulation of Mechanical Properties of Reinforced Red-Sandstone Granular Soil Based on 3D Discrete Element Method

2013 ◽  
Vol 353-356 ◽  
pp. 802-805
Author(s):  
Jian Qing Jiang
Keyword(s):  
Mechanical Properties ◽  
Discrete Element Method ◽  
Triaxial Compression ◽  
Discrete Element ◽  
Reinforced Soil ◽  
Triaxial Tests ◽  
Granular Soil ◽  
Compression Tests ◽  
Red Sandstone ◽  
Element Method

Red-sandstone granular soil reinforced with gabion-mesh is a new concept of composite reinforced soil. In order to reveal the mechanical properties of this composite reinforced soil, a series of laboratory triaxial compression tests on specimens reinforced with gabion-mesh were carried out, and 3D discrete element method was introduced to simulate the triaxial tests. The macro stress-strain relation of red-sandstone specimens reinforced with gabion-mesh was reproduced by the 3D discrete element model. The results show that 3D discrete element method is an ideal technique to study the meso-mechanical nature characteristics of gabion-mesh reinforced red-sandstone granular soil.

Experimental behaviour and modelling of an unsaturated compacted soil

2000 ◽  
Vol 37 (4) ◽  
pp. 748-763 ◽  
Author(s):  
Celestino Rampino ◽  
Claudio Mancuso ◽  
Filippo Vinale
Keyword(s):  
Unsaturated Soils ◽  
Mechanical Response ◽  
Stress Path ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Experimental Program ◽  
State Variables ◽  
Soil Response ◽  
Optimum Water Content ◽  
Triaxial Cell

This paper reports the experimental study and modelling of the mechanical response of a silty sand used in the core of the Metramo dam, Italy. Specimens were prepared by compacting the soil at optimum water content conditions using the modified Proctor technique. Tests were performed under suction-controlled conditions by a stress path triaxial cell and an oedometer. The experimental program consists of 23 tests carried out in the suction range of 0-400 kPa. The findings indicate the strong influence of suction on compressibility, stiffness, and shear strength. The mechanical properties of the soil improve with suction following an exponential law with decreasing gradient. Furthermore, the soil exhibited collapsible behaviour upon wetting even at low stress levels. Interesting results were also achieved in elastoplastic modelling as well. The results led to characterization of soil behaviour with reference to widely accepted modelling criteria for unsaturated soils, providing noteworthy suggestions about their applicability for granular materials with a non-negligible fine component. Finally, some remarks are made for the extension under unsaturated conditions of the "Nor sand" model for saturated granular soils. The proposed approach yields improved predictions of deviator soil response of the tested soil when Cambridge-type frameworks prove invalid.Key words: unsaturated soils, stress state variables, triaxial tests, oedometer tests, constitutive model.

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