Modulus−suction−moisture relationship for compacted soils

2008 ◽  
Vol 45 (7) ◽  
pp. 973-983 ◽  
Author(s):  
Auckpath Sawangsuriya ◽  
Tuncer B. Edil ◽  
Peter J. Bosscher
Keyword(s):  
Shear Modulus ◽  
Empirical Relation ◽  
Small Strain ◽  
Matric Suction ◽  
Unit Weight ◽  
Bender Elements ◽  
Compacted Soils ◽  
Subgrade Soils ◽  
Dry Unit Weight ◽  
Propagation Technique

The ultimate parameter of interest in engineering design of compacted subgrades and support fills for highways, railroads, airfields, parking lots, and mat foundations is often the soil modulus. Modulus of compacted soils depends not only on dry unit weight and moisture but also on matric suction and soil structure (or fabric) resulting from the compaction process. However, these relationships in the as-compacted state (i.e., immediately after compaction) have not yet been extensively explored. This paper presents an experimental laboratory study of the shear modulus – matric suction – moisture content-dry unit weight relationship using three compacted subgrade soils. Compacted subgrade specimens were prepared over a range of molding water contents from dry to wet of optimum using enhanced, standard, and reduced Proctor efforts. A nondestructive elastic wave propagation technique, known as bender elements, was used to assess the shear wave velocity and corresponding small-strain shear modulus (Go) of the compacted subgrade specimens. The matric suctions were measured with the filter paper method. An empirical relation that takes into account the effect of compaction conditions is proposed for the Go – matric suction – molding water content relationship of compacted subgrade soils.

Dry unit weight of compacted soils prediction using GMDH-type neural network

2017 ◽  
Vol 132 (8) ◽  
Author(s):  
Mahmoud Hassanlourad ◽  
Alireza Ardakani ◽  
Afshin Kordnaeij ◽  
Hossein Mola-Abasi
Keyword(s):  
Neural Network ◽  
Unit Weight ◽  
Compacted Soils ◽  
Dry Unit Weight

Impacts of matric suction equalization on small strain shear modulus of soils during air drying

2020 ◽  
Vol 57 (12) ◽  
pp. 1982-1997
Author(s):  
Thang Pham Ngoc ◽  
Behzad Fatahi ◽  
Hadi Khabbaz ◽  
Daichao Sheng
Keyword(s):  
Shear Modulus ◽  
Water Content ◽  
Soil Sample ◽  
Closed System ◽  
Small Strain ◽  
Matric Suction ◽  
Drying Process ◽  
Air Drying ◽  
Small Strain Shear Modulus ◽  
The Impact

In this study, a weight-control bender element system has been developed to investigate the impact of matric suction equalization on the measurement of small strain shear modulus (Gmax) during an air-drying process. The setup employed is capable of measuring the shear wave velocity and the corresponding Gmax of the soil sample in either an open system in which the soil sample evaporates freely or in a closed system that allows the process of matric suction equalization. The comparison between measurements of Gmax in the open and closed systems revealed underestimations of Gmax when matric suction equalization was ignored due to the nonuniform distribution of water content across the sample cross-sectional area. This study also investigated the time required for matric suction equalization tse to be established for samples with different sizes. The experimental results indicated two main mechanisms driving the matric suction equalization in a closed system during an air-drying process, namely the hydraulic flow of water and the flow of vapour. While the former played the key role when the micropores were still saturated at the high range of water content, effects of the latter increased and finally dominated when more air invaded the micropores at lower water contents.

Effects of wetting–drying and stress ratio on anisotropic stiffness of an unsaturated soil at very small strains

2009 ◽  
Vol 46 (9) ◽  
pp. 1062-1076 ◽  
Author(s):  
C. W.W. Ng ◽  
J. Xu ◽  
S. Y. Yung
Keyword(s):  
Unsaturated Soils ◽  
Stress Ratio ◽  
Shear Stiffness ◽  
Small Strain ◽  
Matric Suction ◽  
Bender Elements ◽  
Shear Moduli ◽  
Small Strains ◽  
Stiffness Anisotropy ◽  
Stress Dependent

The very small strain shear modulus of soil, G0, is affected by many factors including soil properties, current stress state, stress history, and matric suction. Very little research has been conducted on anisotropic shear moduli of unsaturated soils. In this study, the effects of wetting–drying and stress ratio on anisotropic shear stiffness of an unsaturated completely decomposed tuff (CDT) at very small strains have been investigated using a modified triaxial testing system equipped with three pairs of bender elements. During drying and wetting tests, the measured very small strain shear moduli increased in a nonlinear fashion, but at a reduced rate as the matric suction increased. Similar to the stress-dependent soil-water characteristic curves (SDSWCCs), there was hysteresis between the drying and wetting curves showing the variations in shear moduli with matric suction. Variation in suction on the specimens under isotropic conditions produced changes in stiffness anisotropy (expressed as G0(hh)/G0(hv)) together with anisotropic strains. In shearing tests at constant suctions, significant stress-induced stiffness anisotropy was observed due to a change in the stress ratio. While shearing at a constant stress ratio, G0(hh)/G0(hv) appeared to be constant.

scholarly journals Estimation of Resilient Modulus for Coarse-Grained Subgrade Soils from Quick Shear Tests for Mechanistic-Empirical Pavement Designs

Designs ◽  
2019 ◽  
Vol 3 (4) ◽  
pp. 48
Author(s):  
Md Mostaqur Rahman ◽  
Kazi Moinul Islam ◽  
Sarah Gassman
Keyword(s):  
South Carolina ◽  
Moisture Content ◽  
Resilient Modulus ◽  
Tangent Modulus ◽  
Coarse Grained ◽  
Unit Weight ◽  
Index Properties ◽  
Subgrade Soils ◽  
Dry Unit Weight ◽  
Technical Ability

The resilient modulus represents the subgrade soil stiffness, and it is considered one of the key material inputs in the Mechanistic Empirical Pavement Design Guide (MEPDG). The resilient modulus is typically estimated in the laboratory using a repeated load cyclic triaxial test, which is complex and time consuming to perform. Technical ability is also required to prepare the test specimens, particularly for coarse-grained soils. Therefore, there is a need to estimate the resilient modulus of coarse-grained soils from other simpler tests. In this study, correlations of resilient modulus with soil index properties and quick shear (QS) test results (quick shear strength, stress at 1% strain and tangent modulus) were developed for remolded coarse-grained soils, collected from different geographic regions in South Carolina. The developed models showed good correlations of resilient modulus to tangent modulus and soil index properties. The average tangent, modulus obtained from 30% and 50% of maximum stress of the QS tests, moisture content, optimum moisture content, dry unit weight, and maximum dry unit weight showed a statistically significant effect on estimating the resilient modulus for coarse-grained subgrade soils. The validation study confirms that the developed models can be used for predicting the resilient modulus for South Carolina coarse-grained soils.

scholarly journals Forensic Evaluation of Compacted Soils using RAMCODES

2018 ◽  
Vol 4 (10) ◽  
pp. 2275 ◽  
Author(s):  
Romer D. Oyola-Guzmán ◽  
Rómulo Oyola-Morales
Keyword(s):  
Bearing Capacity ◽  
Water Content ◽  
Unit Weight ◽  
Strength Analysis ◽  
Construction Site ◽  
Compacted Soils ◽  
Compacted Soil ◽  
Dry Unit Weight ◽  
Heavy Equipment ◽  
Proctor Test

Unexpected failure of compacted soils was explained using design curves of the Rational Methodology for Compacted Geomaterial’s Density and Strength Analysis (RAMCODES).  Forensic geotechnical evaluation, applied to a compacted soil used at a construction site, demonstrated that the bearing capacity of the soil was influenced by the water content and the dry unit weight. At the construction site, the only criterion used for quality control of the compacted soil was the minimum compaction percentage; the maximum dry unit weight (achieved using the standard Proctor test) was used when the soil was compacted with light equipment, and the maximum dry unit weight (achieved using the modified Proctor test) was used when it was compacted with heavy equipment. After changing water content conditions, the soil compacted with heavy equipment and the soil compacted with light equipment exhibited changes in bearing capacity; the soil compacted with light equipment showed a failure, whereas the soil compacted with heavy equipment did not. The causes of failure were evaluated from samples of soil analyzed in the laboratory; analysis was performed using design curves obtained through a factorial experimental design. Our analysis revealed that the criterion of minimum compaction percentage was not adequate to determine the actual mechanical performance of the soil. We sought to determine why the soil compacted with light equipment did not satisfy the bearing capacity expected after compaction, and what other actions should performed at a construction site to avoid failure of soils compacted with light equipment. 

scholarly journals Maximum shear modulus of calcareous sand in Dejebel Dahar, Tunisia and its dependency on applied stress

2019 ◽  
Vol 92 ◽  
pp. 04007 ◽  
Author(s):  
Hyunwook Choo ◽  
Minhyuk Kwon ◽  
Lamia Touiti ◽  
Young-Hoon Jung
Keyword(s):  
Experimental Investigation ◽  
Shear Modulus ◽  
Applied Stress ◽  
Shear Wave Velocity ◽  
Small Strain ◽  
Silica Sand ◽  
Particle Crushing ◽  
Bender Elements ◽  
Calcareous Sand ◽  
Stress Dependency

The present experimental investigation aims at investigating the small strain stiffness of calcareous sand as a function of applied stress. The calcareous sand was sampled at Tunisia's Dejebel Dahar region, and the shear wave velocity (Vs) of calcareous sand was measured using modified oedometer cell equipped with bender elements. The results of this study demonstrate that the Vs of the tested calcareous sand is smaller than that of silica sand with minimal crushable particles at relatively low applied stress (σ); however, Vs of calcareous sand is greater than that of silica sand at high σ, reflecting strong dependency of calcareous sand on σ. The applied stress dependency of soils can be expressed as a power function of applied stress (Vs = α (σ / 1 kPa)β, where α = Vs at σ = 1 kPa and β = stress exponent). Generally, the single α-β can capture the dependency of Vs on σ, and the typical β value for sand is around 0.25. The measured β of tested silica sand was around 0.20; while, Tunisia calcareous sand shows β of greater than 0.32, and the dependency of Vs on σ cannot be captured by single α-β. This can be attributed to the fact that the variation of Vs of tested calcareous sand with increasing σ reflects not only fabric change but also particle crushing.

scholarly journals Piezoelectric Ring Bender for Characterization of Shear Waves in Compacted Sandy Soils

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1226
Author(s):  
Dong-Ju Kim ◽  
Jung-Doung Yu ◽  
Yong-Hoon Byun
Keyword(s):  
Shear Modulus ◽  
Water Content ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Shear Waves ◽  
Small Strain ◽  
The Other ◽  
Compacted Soils ◽  
Small Strain Shear Modulus

Shear wave velocity and small-strain shear modulus are widely used as the mechanical properties of soil. The objective of this study is to develop a new shear wave monitoring system using a pair of piezoelectric ring benders (RBs) and to evaluate the suitability of RB in compacted soils compared with the bender element and ultrasonic transducer. The RB is a multilayered piezoelectric actuator, which can generate shear waves without disturbing soils. For five compacted soil specimens, the shear waves are monitored by using three different piezoelectric transducers. Results of time-domain response show that the output signals measured from the RB vary according to the water content of the specimen and the frequency of the input signal. Except at the water content of 9.3%, the difference in the resonant frequencies between the three transducers is not significant. The shear wave velocities for the RB are slightly greater than those for the other transducers. For the RB, the exponential relationship between the shear wave velocity and dry unit weight is better established compared with that of the other transducers. The newly proposed piezoelectric transducer RB may be useful for the evaluation of the shear wave velocity and small-strain shear modulus of compacted soils.

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