New method to determine proper strain rate for constant rate-of-strain consolidation tests

2012 ◽  
Vol 49 (1) ◽  
pp. 18-26 ◽  
Author(s):  
A. Tolga Ozer ◽  
Evert C. Lawton ◽  
Steven F. Bartlett
Keyword(s):  
Strain Rate ◽  
Linear Equation ◽  
Pore Pressure ◽  
Void Ratio ◽  
Semiempirical Method ◽  
The Other ◽  
Initial Void Ratio ◽  
Constant Rate ◽  
Loading Tests ◽  
Incremental Loading

The development of a new semiempirical method to predict the proper strain rate for constant rate-of-strain (CRS) consolidation tests is described herein. The validity of the proposed method is analyzed using experimental results from CRS and incremental loading tests on four types of soil: Lake Bonneville clay, Massena clay, kaolinite, and montmorillonite. It is found that the maximum allowable strain rate depends on the initial void ratio of the soil and thus is related to the compressibility of the soil. The effect of the strain rate on the distribution of the pore pressure within the sample is investigated by comparing values of effective vertical stress calculated using a linear equation published by Wissa et al. in 1971 with values of effective stress at the base of the specimen determined from measured values of pore pressure. Overall, the proposed method predicts the maximum allowable strain rate very well for three of the four soils and moderately well for the other soil.

Weighted residual approach to constant strain rate test

2011 ◽  
Vol 48 (4) ◽  
pp. 671-675 ◽  
Author(s):  
Dieter Stolle ◽  
Jonathan Stolle
Keyword(s):  
Strain Rate ◽  
Pore Pressure ◽  
Constant Strain Rate ◽  
Time Factors ◽  
Transient Effects ◽  
Coefficient Of Consolidation ◽  
Virtual Displacement ◽  
Constant Rate ◽  
Rate Test ◽  
Displacement Approach

This note presents a virtual displacement approach to analyze the constant rate of strain consolidation test. It yields simplified “exact” equations within the weighted residual context for interpreting test data. Equations corresponding to larger time factors are similar to those presented in the literature, although the transient effects are clearer than in previous formulations. An advantage of the framework is that assumptions concerning the uniformity of properties through a sample can be relaxed. The derivation shows that E must be constant for the coefficient of consolidation to be independent of position. Depending on the sequencing of sublayers, it is shown that basal pore pressure can be higher or lower for layered media compared with uniform material when allowing E to vary, even though cv is kept constant.

Compressibility and Permeability of Sand-Silt Tailings Mixtures

2022 ◽  
Author(s):  
Jiying Fan ◽  
R. Kerry Rowe ◽  
Richard W.I. Brachman
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Published Data ◽  
Internal Stability ◽  
Fines Content ◽  
Coarse Grains ◽  
Soil Skeleton ◽  
Loading Tests ◽  
Stress Dependent ◽  
Incremental Loading

Microstructure showing the involvement of the fine and coarse grains in the soil skeleton is evaluated. Incremental loading tests using a stress-dependent permeameter are conducted on the mixtures of poorly graded sand and nonplastic fines originating from tailings. The results are compared with the published data of various tailings. It is shown that increasing the fines content from 0 to 100%, the involvement of the fine and coarse components of soil skeleton can be classified into four categories: no fines involvement (<10% fines), fines partially involved (10% —35% fines), increasing cushioning effect surrounding the coarse (35% — 40% fines), and constant cushioning effect (> 40% fines). At the same consolidation stress, the void ratio, e, rapidly decreases for fines less than 30%, then almost remains constant between 30% and 50% fines, and gradually increases for fines exceeding 50%. The hydraulic conductivity, k, decreases more than 20-fold as the fines content increases from 12% to 50%, then remains constant. k is proportional to [e3/(1+e)]A and inversely proportional to S2, where A is a factor describing the effect of particle angularity and S is the specific surface. Finally, the influence of fines content on the seepage-induced internal stability is discussed.

Constant rate of strain consolidation testing of soft clays and fibrous peats

2019 ◽  
Vol 56 (10) ◽  
pp. 1526-1533
Author(s):  
Gholamreza Mesri ◽  
Tao-Wei Feng
Keyword(s):  
Strain Rate ◽  
Flow Equation ◽  
Test Duration ◽  
Soft Clays ◽  
Vertical Strain ◽  
Empirical Correction ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Specimen Quality ◽  
Incremental Loading

The constant rate of strain (CRS) oedometer test, using an imposed vertical strain rate [Formula: see text] equal to 10 times the end-of-primary (EOP) vertical strain rate [Formula: see text], requiring a test duration of about 2 days produces reliable information on both the e versus log[Formula: see text] relation and e versus logkv relation of soft clays and fibrous peats. An empirical correction for the strain rate effect on preconsolidation pressure leads to the EOP e versus log[Formula: see text] relation and EOP [Formula: see text]. The imposed vertical strain rate [Formula: see text] produces excess pore-water pressures at the impervious bottom of the specimen, corresponding to [Formula: see text] values in the range of 3%–15% and allows, use of the Darcy flow equation, a reliable calculation of the coefficient of permeability. Compressibility and permeability data are from CRS and incremental loading (IL) oedometer tests on specimen quality designation (SQD) A samples of seven soft clays and two fibrous peats are presented in this paper.

scholarly journals Influential Factors of the Static Shear Properties of Coral Mud in the South China Sea

2020 ◽  
Vol 2020 ◽  
pp. 1-17 ◽  
Author(s):  
Yang Shen ◽  
Xiaoxi Rui ◽  
Long Yang ◽  
Shaoyu Li ◽  
Xue Shen
Keyword(s):  
South China Sea ◽  
Pore Pressure ◽  
South China ◽  
Void Ratio ◽  
Confining Pressure ◽  
Stress Path ◽  
The South China Sea ◽  
Initial Void Ratio ◽  
Static Shear ◽  
Cam Clay

Coral mud, a kind of special material used for constructing islets in reclamation projects, is widely spread in the South China Sea. Combined with microstructure research, a series of triaxial tests were performed in this paper to study the static shear strength characteristics and potential factors that can influence them. The effective stress path was similar to the total stress path because of the unique microstructure resulting in a high strength and a high dissipation rate of the pore pressure in the coral mud. The initial void ratio and the initial confining pressure affected the strength and deformation characteristics of the coral mud. When the soil came to failure, the pore pressure coefficient Af varied linearly with the initial void ratio. The critical friction angle was greatly influenced by the confining pressure, and its magnitude first developed to a peak value and then decreased as the void ratio increased. This change showed that there was a linear relationship between the initial elastic modulus E0i and lgp0 as well as between the secant modulus E50 and p0. The estimation ability of Cam-Clay was verified in this research. The value of parameter λ was determined incrementally by a larger initial void ratio, while the value of parameter M decreased smoothly first and then rose slightly; the selection of parameter κ was approximately 0.0035. The results supported that the Cam-Clay model is able to simulate the stress-strain relationship of coral mud, and a referenced estimation can be reliably and efficiently obtained for the reclamation projects of constructing islets.

scholarly journals Numerical Simulation to Select Proper Strain Rates during CRS Consolidation Test

2017 ◽  
Author(s):  
Abderrahmane Henniche ◽  
Smain Belkacemi
Keyword(s):  
Numerical Simulation ◽  
Liquid Limit ◽  
Strain Rates ◽  
Relative Pressure ◽  
Simple Method ◽  
Initial Void Ratio ◽  
Rate Dependent ◽  
Constant Rate ◽  
Good Agreement ◽  
Incremental Loading

Constant rate of strain (CRS) and incremental loading (IL) consolidation tests are extensively used to measure consolidation properties of clayey soils. However, results of CRS test are usually strain rate dependent. In this study, a finite differences simulation of CRS test based on Terzaghi’s theory of consolidation is performed. The numerical simulation permits to evaluate a strain rates range satisfying a preset relative pressure criterion. Results of simulation show that the required relative pressure criterion can be verified, during the steady state stage of CRS test, only for particular types of soils and particular range of strain rates. Subsequently, a simple method is proposed to select, for a soil sample defined by its initial height, initial void ratio and liquid limit, an appropriate strain rates range satisfying the ASTM 4186-06 criterion. Comparison of previsions and experimental results reported in literature shows good agreement.

Effect of strain rate, off-axis loading and high-velocity impact damage on the compressive strength of C/SiC composite

2018 ◽  
Vol 53 (4) ◽  
pp. 535-546 ◽  
Author(s):  
M Altaf ◽  
S Singh ◽  
VV Bhanu Prasad ◽  
Manish Patel
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
High Velocity ◽  
Impact Damage ◽  
The Other ◽  
High Velocity Impact ◽  
Fibre Bundles ◽  
Velocity Impact ◽  
Kink Bands ◽  
Other Hand

The compressive strength of C/SiC composite at different strain rates, off-axis orientations and after high-velocity impact was studied. The compressive strength was found to be 137 ± 23, 130 ± 46 and 162 ± 33 MPa at a strain rate of 3.3 × 10−5, 3.3 × 10−3, 3.3 × 10−3 s−1, respectively. On the other hand, the compressive strength was found to be 130 ± 46, 99 ± 23 and 87 ± 9 MPa for 0°/90°, 30°/60° and 45°/45° fibre orientations to loading direction, respectively. After high-velocity impact, the residual compressive strength of C/SiC composite was found to be 58 ± 26, 44 ± 18 and 36 ± 3.5 MPa after impact with 100, 150 and 190 m/s, respectively. The formation of kink bands in fibre bundles was found to be dominant micro-mechanism for compressive failure of C/SiC composite for 0°/90° orientation. On the other hand, delamination and the fibre bundles rotation were found to be the dominant mechanism for off-axis failure of composite.

Mode based characterisation of swell deformations in a high plasticity Paleogene clay

2021 ◽  
Author(s):  
Emil Mejlhede Kinslev ◽  
Ole Hededal ◽  
Irene Rocchi ◽  
Varvara Zania
Keyword(s):  
Deformation Behaviour ◽  
Accurate Prediction ◽  
High Plasticity ◽  
Complex Deformation ◽  
Constant Rate ◽  
Incremental Loading

Accurate prediction of soil deformations is important in unloading as well as loading. Historically, however, the loading scenario has been the most common and thus the most extensively studied phenomenon, leaving unloading less well described. Overconsolidated high plasticity clays are particularly challenging in this regard due to their complex deformation behaviour that has previously shown two conceptually different unloading behaviours. Based on a series of incremental loading and constant rate of strain compression and swelling tests on folded Røsnæs Clay, these unloading behaviours are unified in a framework as different swell modes, and an additional swell mode is identified. These different modes represent a variation in swell inhibiting structure, seemingly unrelated to the structure in compression. The use of constant rate of strain tests greatly enhanced the detailed description of stiffness development in each mode, which may be characterised by up to three swell phases. The parameters governing the occurrence of the swell modes are identified along with the variables that define the transition between the swell phases and their detailed development.

Two types of reservoir-induced seismicity

1988 ◽  
Vol 78 (6) ◽  
pp. 2025-2040
Author(s):  
D.W. Simpson ◽  
W.S. Leith ◽  
C.H. Scholz
Keyword(s):  
Normal Stress ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Elastic Stress ◽  
Pore Space ◽  
Temporal Distribution ◽  
The Other ◽  
Elastic Response ◽  
Reservoir Induced Seismicity ◽  
Effective Normal Stress

Abstract The temporal distribution of induced seismicity following the filling of large reservoirs shows two types of response. At some reservoirs, seismicity begins almost immediately following the first filling of the reservoir. At others, pronounced increases in seismicity are not observed until a number of seasonal filling cycles have passed. These differences in response may correspond to two fundamental mechanisms by which a reservoir can modify the strength of the crust—one related to rapid increases in elastic stress due to the load of the reservoir and the other to the more gradual diffusion of water from the reservoir to hypocentral depths. Decreased strength can arise from changes in either elastic stress (decreased normal stress or increased shear stress) or from decreased effective normal stress due to increased pore pressure. Pore pressure at hypocentral depths can rise rapidly, from a coupled elastic response due to compaction of pore space, or more slowly, with the diffusion of water from the surface.

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