Investigation of small- to large-strain moduli correlations of normally consolidated granular soils

2021 ◽  
Vol 58 (1) ◽  
pp. 1-22
Author(s):  
Ibrahim Lashin ◽  
Michael Ghali ◽  
Mahmoud N. Hussien ◽  
Mohamed Chekired ◽  
Mourad Karray
Keyword(s):  
Large Strain ◽  
Small Strain ◽  
In Situ Stress ◽  
Soil Parameters ◽  
Physical Parameters ◽  
Granular Soils ◽  
Shear Wave Velocities ◽  
Settlement Behavior ◽  
Constrained Modulus

The establishment of correlations between the small-strain shear modulus (Go) and other soil parameters (such as the oedometer constrained modulus, Moedo) at large deformations constitutes an important step toward more precise modeling of soil deformation behavior. In this study, the shear wave velocities (Vs) of 22 different granular soils of various physical characteristics were measured experimentally using the piezoelectric ring-actuator technique (P-RAT) incorporated in the conventional oedometer cell. For each sample tested, the development of Moedo with the development of relative density (Id), as well as the void ratio (e), was recorded. Then, the obtained Vs and Moedo/Go trends were correlated to the physical parameters of the tested granular soils with the development of e and Id. A practical application employing the achievements in geotechnical engineering design was also evaluated. Based on the proposed correlations, geotechnical designers can easily estimate in situ stress–settlement behavior from the predicted Moedo and Id values using simple in situ measurements.

Investigation of Small- to Large-Strain Moduli Correlations of Rockfill Materials – Application to Romaine-2 Dam

2021 ◽  
Author(s):  
Ibrahim Lashin ◽  
Michael Ghali ◽  
Marc Smith ◽  
Daniel Verret ◽  
Mourad Karray
Keyword(s):  
Large Strain ◽  
Deformation Behaviour ◽  
Numerical Data ◽  
Small Strain ◽  
Hyperbolic Model ◽  
Large Strains ◽  
Initial Modulus ◽  
Rockfill Materials ◽  
Materials Used

Establishment of a relationship between the shear wave velocity (Vs) and other geotechnical parameters of rockfill soils at large strains (oedometer modulus, Moedo, tangent modulus, Et) is considered a significant step towards more precise modelling of earth-structure deformation behaviour. In this study, four samples of different gradations, reconstituted from the rockfill materials used in the construction of the Romaine-2 dam, were experimented to correlate the small strain to large strain moduli. Development of Moedo and Vs with consolidation was measured in the laboratory using the piezoelectric ring-actuator technique (P-RAT) incorporated in a large oedometer. Therefore, a correlation between Moedo and small strain shear modulus Go was proposed. Moreover, numerical simulations were performed based on the Duncan-Chang hyperbolic model to correlate the Vs to Duncan-Chang initial modulus(Ei). Based on the experimental and numerical data, a relation between Ei and Vs of the tested rockfill has been established. Verification studies were also carried out on in-situ measurements during Romaine-2 dam construction, proofing the ability of the proposed relationships to predict Ei related to the minor principal stress (σ3) from in-situ Vs measurement. The proposed correlations could help the geotechnical designers to estimate accurately the deformation of rockfill materials from in-situ Vs measurement.

scholarly journals Study of the influencing factors of the liquid CO2 phase change fracturing effect in coal seams

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254996
Author(s):  
Jinzhang Jia ◽  
Dongming Wang ◽  
Bin Li ◽  
Xiuyuan Tian
Keyword(s):  
Coal Seam ◽  
Phase Change ◽  
Peak Pressure ◽  
In Situ Stress ◽  
Simulation Software ◽  
Hole Diameter ◽  
Gas Pressure ◽  
Physical Parameters ◽  
Simulation Results

To study the influence of different factors on the cracking effect of the liquid CO2 phase transition, the mechanics of coal rock crack extension based on liquid CO2 phase change blast loading were studied. Through the application of simulation software to analyze the influence of coal seam physical parameters (in situ stress, gas pressure, modulus of elasticity and strength of coal) and blasting parameters (fracturing pore size and peak pressure of detonation)on the effect of liquid CO2 phase change cracking, the simulation results showed that the cracking effect of liquid CO2 phase change was positively correlated with the changes in gas pressure, elastic modulus, fracture hole diameter and peak vent pressure, negatively correlated with the variation in situ stress and compressive strength, and nearly independent of the tensile strength. In addition, by using Gray correlation analysis to analyze the influence degree of six main factors on the cracking effect, the calculation results showed that the effect of blasting parameters was greater than that of physical parameters. The main controlling factor that affected the blasting effect was the peak pressure of blasting release. By conducting comparative engineering trials with different blasting parameters, the test results showed that the crack effect of the coal seam was positively correlated with the change in fracture hole diameter and peak venting pressure, which was consistent with the results obtained from the simulation. The experimental results and simulation results for the effective radius of coal seam fracturing were basically consistent, with the error between the two types of results falling below 10%. Therefore, the reliability of the blasting numerical model was verified. In summary, the research results provide theoretical guidance for applying and promoting liquid CO2 fracturing technology in coal mines.

New equipment for densification of granular soils at depth

1990 ◽  
Vol 27 (2) ◽  
pp. 167-176
Author(s):  
R. G. Campanella ◽  
R. Hitchman ◽  
W. E. Hodge
Keyword(s):  
Field Testing ◽  
Independent Study ◽  
Soil Parameters ◽  
Granular Soils ◽  
In Situ Tests ◽  
River Sand ◽  
University Of British Columbia ◽  
A Site ◽  
The Phoenix

An in situ densification probe that employs the novel technique of simultaneous vibration and dewatering has been developed by Phoenix Engineering Ltd. to compact deep, loose, granular soils. It is believed that pumping water out of the soil during the densification process offers improved densification capability over systems operating with vibration alone. An independent study was undertaken by the In-Situ Testing Group at the University of British Columbia to evaluate the performance of the Phoenix system.A field testing programme was conducted at a site in Vancouver where hydraulic sand fill overlies a natural silt and then medium Fraser River sand. Characterization of the site and evaluation of the densification treatment process were achieved using in situ tests. Changes to soil parameters due to densification treatment were examined, taking into account the modification of stresses brought about by the vibro-drainage process. The study investigated the degree of densification achieved, the value of concurrent drainage, the zone of influence of a single compaction probe, and group effects. The study also compares the performance of the Phoenix machine with that of other vibrocompaction equipment. Key words: in situ, densification, soils, granular, probe, vibratory, drainage, compaction, R&D.

scholarly journals Estimating the Small Strain Stiffness of Peat Soil Using Geophysical Methods

2021 ◽  
Vol 7 (1) ◽  
pp. 44-54
Author(s):  
Kasbi Basri ◽  
Adnan Zainorabidin ◽  
Mohd Khaidir Abu Talib ◽  
Norhaliza Wahab
Keyword(s):  
Peat Soil ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Small Strain ◽  
In Situ Stress ◽  
Design Parameters ◽  
Small Strain Stiffness ◽  
Geotechnical Design ◽  
Sample Disturbance

Geotechnical design commonly requires that the in-situ stiffness, strength and permeability of the ground be obtained. Laboratory based investigation often related with risk of sample disturbance and difficulties to replicate the in-situ stress condition which results in overestimation or underestimation. Application of geophysical methods in geotechnical investigation previously was limited to targeting and dimensioning sub-surface features due to lack of resolution. However, rapid developments of geophysical methods result in the application of these methods in providing geotechnical design parameters. Multichannel analysis of surface waves (MASW) and seismic refraction were among the geophysical methods capable of obtaining stiffness parameters including the maximum shear modulus (Gmax) and maximum elastic modulus (Emax). The study revealed the efficiency of these methods to measure the small strain stiffness of peat soil with high accuracy as the results obtained were found to be similar to those obtained by previous researchers. Overall, the Gmax and Emax values of peat soil obtained range from 0.49 to 1.72 MPa and 1.46 to 5.15 MPa respectively. The Gmax and Emax values obtained shows significant increase with depth governed primarily by the effective stress. Other parameters such as degree of decomposition and peat thickness also shows potential influence on the Gmax and Emax values obtained.

Influence of Geometrical and Physical Parameters of Cement on Loads of Casing and Cement

2013 ◽  
Vol 634-638 ◽  
pp. 3591-3594
Author(s):  
Xiao Zeng Wang ◽  
Zhan Qu ◽  
Yi Hua Dou
Keyword(s):  
Young’S Modulus ◽  
Mechanical Model ◽  
Radial Stress ◽  
Young's Modulus ◽  
In Situ Stress ◽  
Stress Conditions ◽  
Poisson's Ratio ◽  
Physical Parameters ◽  
Continuous Displacement

A mechanical model of casing, formation and cement is established under the action of the in-situ stress in the cementing section. According to the continuous displacement and radial stress conditions, the calculation formulas of loads applied to casing and cement are developed. The influences of geometrical and physical parameters of cement on loads and stresses of the casing and cement are analyzed. The result shows that the increase of Young’s modulus of cement results in that the casing load increases firstly, and then decreases. The bigger Young’s modulus of cement, the more load of cement. Along with the increase of Poisson's ratio of cement, cement and casing load become bigger. Cement load is greater than the casing one, so it can avoid damaging casing.

scholarly journals Very-small to large strain dynamic behaviour of unsaturated sand in a wide range of suction

2020 ◽  
Vol 195 ◽  
pp. 03002
Author(s):  
Ali Akbar Karimezadeh ◽  
Fardin Jafarzadeh ◽  
Anthony Kwan Leung ◽  
Adel Ahmadinezhad
Keyword(s):  
Transition Zone ◽  
Unsaturated Soil ◽  
Simple Shear ◽  
Dynamic Properties ◽  
Large Strain ◽  
Damping Ratio ◽  
Small Strain ◽  
Soil Parameters ◽  
Static And Dynamic Analysis ◽  
Wide Range

Shear modulus (Gmax at very small strain and G at large strain) and constraint modulus at very small strain (M) are important soil parameters for static and dynamic analysis in geotechnical applications. However, these dynamic properties of unsaturated soil are rarely reported. In this study, a cyclic simple shear apparatus was newly-modified for allowing both the shear and constrained moduli at both very small and large strains to be measured. Benders or ultrasonic sensors were embedded in an unsaturated soil sample for transmitting/receiving shear- and pressure-wave, respectively. Two very-small-strain tests were conducted to determine the Gmax, M and soil damping ratio of a sand for a wide range of suction covering from the boundary-effect, transition and residual zone of the water retention curve of the sand. In addition, six large-strain cyclic simple shear tests were carried out to investigate G. The test results showed that Gmax and M were approximately constant before reaching the air-entry value, but there was a significant increase in Gmax as the sand dried further. Yet, M dropped within the transition zone, and interestingly when the suction was beyond the residual value, M increased. M along the wetting path was higher than that along the drying path. The damping ratio, on the other hand, first reduced before reaching the air-entry value, but it increased at the transition zone and then decreased within the residual zone. At large strain, G/Gmax also increased as suction increased until reaching the residual zone, beyond which the normalised value show substantial decreased.

scholarly journals Development of a Stress Sensor for In-Situ High-Pressure Deformation Experiments Using Radial X-Ray Diffraction

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 166
Author(s):  
Jennifer Girard ◽  
Reynold E. Silber ◽  
Anwar Mohiuddin ◽  
Haiyan Chen ◽  
Shun-ichiro Karato
Keyword(s):  
High Pressure ◽  
Slip System ◽  
Large Strain ◽  
Small Strain ◽  
Average Stress ◽  
X Ray Diffraction ◽  
Stress Sensor ◽  
X Ray ◽  
In Series

We developed a stress sensor for in-situ deformation experiments using synchrotron radial X-ray diffraction. This stress sensor provided nearly diffraction-plane-independent stress that, when used in series with a sample, reduced the uncertainty of the average stress estimation acting on a sample. Here, we present the results of a study where pyrope was used as a stress sensor. Using a Deformation-DIA (D-DIA) high-pressure deformation apparatus, pyrope, olivine and alumina were deformed in the same run/cell assembly placed in series along the compression direction. Deformation experiments were conducted at pressures between 4 and 5 GPa and temperatures between 730 and 1273 K with strain-rates between 10−5 and 10−6 s−1. Stresses estimated from various (hkl) planes in pyrope were nearly the same; i.e., pyrope is plastically isotropic with ≤10 % variation with (hkl). However, stresses from various (hkl) planes in olivine and alumina varied by approximately a factor of 3. Comparisons between average stresses inferred from pyrope and those from different diffraction planes in olivine and alumina showed that the average stress in these materials evolved from low-end stress, estimated from various (hkl) planes at small strain, to high-end stress at a large strain. This suggests that the rate-controlling slip system in these materials changes from the soft to the hard slip system with strain.

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