Experimental Verification of CRS Consolidation Theory

Sheahan, Thomas C.; Watters, Patrick J.

doi:10.1061/(asce)1090-0241(1997)123:5(430)

Cited by 45 publications

(32 citation statements)

References 15 publications

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“…For example based on Wissa et al [15] works it should be less than 0.05, ASTM (D4186-86) propose it between 0.03 until 0.3. However, Sheahan and Watters [13] got correct test results while ratio of pore presser at the bottom of sample to applied stress was more than 71% [13] . Authors didn't find reason of mentioned difference [15] .…”

Section: Introductionmentioning

confidence: 95%

“…Almeida et al [1] conducted some CRS consolidation tests on Brazil clays based on nondimetional parameter which was presented by Lee et al [9] but they didn't get correct results and criticized Lee methods. Actually, CRS consolidation tests several times rejected by some researchers [13,14] . Selection of proper strain rate is an open question in CRS consolidation [3] .…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic Characteristics and Pore Water Flow Rule in Constant Rate of Strain Consolidation

Ahmadi¹,

Hoorfar²,

Rahimi³

et al. 2009

American J. of Applied Sciences

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Problem statement: At present study Constant Rate of Strain (CRS) consolidation under Non-Darcy condition was investigated. Approach: In this study a governing conditions on pore water flow were investigated using proposed equation and experimental tests. CRS experiments under different rates of strain were conducted on different soil samples. Results: Results of these experiments and there comparison with proposed equation showed that flow of pore water flow in the most part of each test was Non-Darcy and changed to Darcy condition in the final almost one forth of tests. Conclusion: According to the results the threshold where Non-Darcy flow changes to Darcy was dependent on variations of relative pore water pressure versus total strain and it can be determined based on variations in inclination of relative pore water pressure-total stress curve.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Hydraulic Characteristics and Pore Water Flow Rule in Constant Rate of Strain Consolidation

Ahmadi¹,

Hoorfar²,

Rahimi³

et al. 2009

American J. of Applied Sciences

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“…Terzaghi et al 1996, Sheahan et al, 1997, Force, 1998 data readings is kept reasonably short and the applied strain rate is slow enough to keep the pore pressure ratio (Δu h /σ v ) less than 5%. However, based on the pore pressures measured at five points through the specimen depth, Sheahan et al (1997) showed that the distribution of pore pressure across the specimen in a CRS consolidation test was approximately parabolic. In this case, the vertical effective stress calculated with the nonlinear solution would be more realistic.…”

Section: Hydraulic Conductivity (K)mentioning

confidence: 99%

Stabilization and Improvement of Organic Soils

Hwang¹,

Humphrey²,

Bobet³

et al. 2005

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Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. AbstractPeats and organic soils in general pose significant problems to geotechnical engineers due to their low strength, high compressibility and elevated creep. The research performed addressed one soil improving technique, deep soil mixing, that has been widely used for treating soft clays, but that especially in the US has found limited use in presence of organic soils. The work performed made use primarily of one soil sampled on Lindberg Road (LR) in West Lafayette, IN characterized by LOI= 45-52%, LL= 327%, PL= 162%, LL oven dried /LL non-dried = 0.31, Gs = 2.05-2.12, fiber content ~2.29%, clay fraction = 40.6%. In addition, a limited number of tests were performed making use of soils with LOI of 10-20%, manufactured in the lab from LR soil and an illitic clay.A procedure was developed for preparing samples of reconstituted LR soil both untreated and mixed with a binder and which included a "curing" stage under a surcharge to simulate treatment at depth. Specimens obtained from these samples were used for the engineering tests which included constant rate of strain (CRS) consolidation tests, end-of-primary incremental loading (EOP-IL) consolidation tests with one long term creep stage, and unconfined compression tests. A battery of characterization tests and an in depth review of the literature complemented this work.Unconfined compression tests provided a preliminary evaluation of the effects of treatment on the strength of the soil; highlighted the effects of curing under a surcharge; and allowed to identify in Portland cement (PC) the most promising binder, which was subsequently used for all other engineering tests, at dosages ranging from 8% (~25 kg/m 3 ) to 100% (~320 kg/m 3 )by dry mass of the soil. The results of the consolidation tests highlighted how the accurate characterization of the primary consolidation behavior of soils characterized by high tendency to creep must rely on either CRS or EOP-IL loading tests and demonstrated the effects of treatment with cement on the stiffness, the hydraulic conductivity, the rate of consolidation and the rate of creep of the soil. Specifically, the tests showed how the addition of cement is associated with the development of a preconsolidation pressure and the shift of the compression curve towards higher effective stresses. Once this yield stress is exceeded the compressibility in the virgin compression range is found not to vary significantly with cement content. Also associated with the addition of cement is an increase in the hydraulic conductivity, an increase in the coefficient of consolidation, and a reduction in the creep coefficient at any given stress level. Moreover, the C α /C c ratio decreases markedly with cement addition indicating a decreased susceptibility of the soil to creep. All these effects are more marked with increasing cement content and the treatment appear especially effective once the PC% exceeds 50% (~160 kg/m 3 ). Key Words...

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“…The solution consists of transient conditions that usually occur at the early stage of loading in which large excess pore water pressures are generated, and steady state conditions corresponding to a constant strain distribution. A dimensionless time factor T was derived for CRS conditions, it indicates the degree of transience in the specimen strain distribution, and is evaluated from a function F3 that at any time equal to A regression analysis of dimensionless time T versus F 3 plot gives a simplified equation for T [7], as:…”

Section: Theoretical Aspect Of Crs Consolidation Testmentioning

confidence: 99%

“…It is adopted by the Swedish geotechnical institute, the Norwegian geotechnical institute, the French Laboratoire Central des Ponts et Chaussées (LCPC), and the American Society of Testing and Materials (ASTM) [4]. However, prior selection of a suitable strain rate for a given soil specimen, is still a problem to an extensive use of the CRS test in practice [4,5], and many researches were conducted to examine strain rate effect on measured CRS consolidation parameters [6][7][8][9].Comparison of CRS test results with those of conventional oedometer test has permitted to develop some criteria for the CRS test results acceptance. These criteria are essentially the relative pressure criterion R u [2,3,10], the liquid limit LL criterion [11], and the standardized strain rate parameter β based on the large strain theory [4,12].…”

mentioning

confidence: 99%

Numerical Simulation to Select Proper Strain Rates during CRS Consolidation Test

Henniche

Belkacemi

2017

Period. Polytech. Civil Eng.

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Constant rate of strain (CRS) and incremental loading (IL)consolidation [3]. Constant rate of strain consolidation test reduces the required time for consolidation test using standard oedometer test (IL) from almost two weeks time to few hours. During CRS test the load is applied continuously; continuous record of stress and deformation are made, which improves the accuracy of consolidation properties determination in particular the preconsolidation pressure P c .Because of its many advantages, the CRS test is in many countries, a standard test for the determination of consolidation properties of clayey soils. It is adopted by the Swedish geotechnical institute, the Norwegian geotechnical institute, the French Laboratoire Central des Ponts et Chaussées (LCPC), and the American Society of Testing and Materials (ASTM) [4]. However, prior selection of a suitable strain rate for a given soil specimen, is still a problem to an extensive use of the CRS test in practice [4,5], and many researches were conducted to examine strain rate effect on measured CRS consolidation parameters [6][7][8][9].Comparison of CRS test results with those of conventional oedometer test has permitted to develop some criteria for the CRS test results acceptance. These criteria are essentially the relative pressure criterion R u [2,3,10], the liquid limit LL criterion [11], and the standardized strain rate parameter β based on the large strain theory [4,12]. The relative pressure criterion R u defined as the ratio of excess pore water pressure at the base of specimen ∆u H to applied vertical stress ∆σv is generally the most used criterion. However, literature survey shows important differences in the acceptable range of relative pressure values. Table 01 summarizes some relative pressure values recommended by authors for some types of soils, with relative pressure range varying from 5 to 50%. ASTM standard (ASTM 4186-06) recommends values of relative pressure to be between 3 and 15% during steady state stage of CRS test [13]. Similar range of relative pressure is also recommended by the French Laboratory (LCPC) [14].

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Experimental Verification of CRS Consolidation Theory

Cited by 45 publications

References 15 publications

Hydraulic Characteristics and Pore Water Flow Rule in Constant Rate of Strain Consolidation

Hydraulic Characteristics and Pore Water Flow Rule in Constant Rate of Strain Consolidation

Stabilization and Improvement of Organic Soils

Numerical Simulation to Select Proper Strain Rates during CRS Consolidation Test

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