Initial Research on Mechanical Response of Unbound Granular Material under Static Load with Various Moisture Content

The freeze-thaw cycles cause deterioration in mechanical properties of levee soil and further endanger the pavement structure on the embankment. This study attempts to comprehensively understand the mechanical response of pavement after freeze-thaw cycles. In this paper, the freeze-thaw cycles test under an open system was carried out, and then the triaxial compression test was conducted. Based on the test results, the effects of freeze-thaw cycles, temperature range, initial dry density, and initial moisture content of embankment soil on the mechanical response of road structure after freeze-thaw were calculated and analyzed. Finally, the stability of the slope of the levee was evaluated. The results show that the number of freeze-thaw cycles has the most significant impact on the mechanical response of pavement, the stress and strain of the structural layers vary in different ranges, and the pavement deflection increases by 5 times after 7 freeze-thaw cycles. However, the initial dry density and initial moisture content of the soil have little influence on the pavement structure, and the temperature range will exert an influence when it exceeds a certain threshold.

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Capacitance Type Moisture Sensors in Unbound Granular Material of Pavement Structures

Lecture Notes in Civil Engineering - Accelerated Pavement Testing to Transport Infrastructure Innovation ◽

10.1007/978-3-030-55236-7_60 ◽

2020 ◽

pp. 583-591

Author(s):

Michael Vrtis ◽

Leonard Palek ◽

Benjamin Worel

Keyword(s):

Granular Material ◽

Pavement Structures ◽

Unbound Granular Material

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Shakedown of unbound granular material

Granular Matter ◽

10.1007/s10035-004-0186-6 ◽

2005 ◽

Vol 7 (2-3) ◽

pp. 109-118 ◽

Cited By ~ 33

Author(s):

R. García-Rojo ◽

H. J. Herrmann

Keyword(s):

Granular Material ◽

Unbound Granular Material

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A new methodology to simulate subglacial deformation of water-saturated granular material

The Cryosphere ◽

10.5194/tc-9-2183-2015 ◽

2015 ◽

Vol 9 (6) ◽

pp. 2183-2200 ◽

Cited By ~ 14

Author(s):

A. Damsgaard ◽

D. L. Egholm ◽

J. A. Piotrowski ◽

S. Tulaczyk ◽

N. K. Larsen ◽

...

Keyword(s):

Granular Material ◽

Pore Water ◽

Mechanical Response ◽

Water Pressure ◽

Shear Zones ◽

Computational Experiments ◽

Unconsolidated Sediments ◽

Close Monitoring ◽

Granular Bed ◽

Water Saturated

Abstract. The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions. Our computational experiments support the findings of previous studies where the rheology of a slowly deforming water-saturated granular bed in the steady state generally conforms to the rate-independent plastic rheology. Before this so-called critical state, deformation is in many cases accompanied by volumetric changes as grain rearrangement in active shear zones changes the local porosity. For previously consolidated beds porosity increases can cause local pore-pressure decline, dependent on till permeability and shear rate. We observe that the pore-water pressure reduction strengthens inter-granular contacts, which results in increased shear strength of the granular material. In contrast, weakening takes place when shear deformation causes consolidation of dilated sediments or during rapid fabric development. Both processes of strengthening and weakening depend inversely on the sediment permeability and are transient phenomena tied to the porosity changes during the early stages of shear. We find that the transient strengthening and weakening in turn influences the distribution of shear strain in the granular bed. Dilatant strengthening has the ability to distribute strain during early deformation to large depths, if sediment dilatancy causes the water pressure at the ice–bed interface to decline. Oppositely, if the ice–bed interface is hydrologically stable the strengthening process is minimal and instead causes shallow deformation. The depth of deformation in subglacial beds thus seems to be governed by not only local grain and pore-water feedbacks but also larger-scale hydrological properties at the ice base.

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Statistical Modelling of the Resilient Behaviour of Unbound Granular Material

Slovak Journal of Civil Engineering ◽

10.2478/sjce-2013-0002 ◽

2013 ◽

Vol 21 (1) ◽

pp. 9-16 ◽

Cited By ~ 1

Author(s):

Elsabe Van Aswegen ◽

Wynand J. Vdm. Steyn

Keyword(s):

Granular Material ◽

Granular Materials ◽

Performance Test ◽

Statistical Modelling ◽

Engineering Properties ◽

Basic Material ◽

Primary Input ◽

Unbound Granular Materials ◽

Quality Material ◽

Unbound Granular Material

Abstract The resilient behaviour of an unsaturated, unbound granular material is a primary input used in the mechanistic analysis of pavements incorporating such layers. Various models exist for the determination of the resilient behaviour, mainly based on the output of tri-axial laboratory testing. This paper describes an investigation where basic engineering properties such as grading, laboratory compaction characteristics and optimum moisture content are incorporated into the resilient behaviour model to quantify the effect of basic material properties on the resilient response of unsaturated, unbound granular materials. Such a resilient behaviour model will enable practitioners to estimate the behaviour of specific material, which might enable the use of available quality material that was discarded in the past. Data from tri-axial laboratory tests on materials originating from the Long Term Pavement Performance test sections are combined with basic engineering parameters of typical unbound granular material through a statistical modelling process to develop a model for predicting resilient behaviour, which can be used as a practical predictor of the expected behaviour during a Level 2 and/or Level 3 Mechanistic Empirical Pavement Design analysis. The work illustrates the process and the potential to develop a general resilient behaviour model for unbound granular materials incorporating saturation effects.

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