Critical Reappraisal of Casagrande and Taylor Methods for Coefficient of Consolidation

Olek, Bartłomiej Szczepan

doi:10.1007/s12205-019-1222-8

Cited by 7 publications

(4 citation statements)

References 29 publications

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“…Moreover, the application of some methods strongly depends on the shape of consolidation curves. Essentially, for soils that do not exhibit theoretical S-shaped settlement-time curves (type I according [33,67]), it is unreasonable to use graphical methods in which the linear part of secondary consolidation should be distinguished from the curve to determine the consolidation parameters [39,44,45]. This inconvenience is associated with the Casagrande method (CA).…”

Section: Predominant Factors Controlling the Rate Of Volume Changementioning

confidence: 99%

“…Given that this is a mono-objective problem, c v with the lowest error was selected and was considered as the optimal value for experimental results. Such approaches have been adopted and validated for various natural and artificial geomaterials by Dobak and Gaszyński [14], Olek and Pilecka [47] and Olek [45]. To carry out the GR method at a suitable level of accuracy, a function that could evaluate the error between the experimental and theoretical solutions and then minimise this function should be defined.…”

Section: Optimisation Msl Consolidation Testsmentioning

confidence: 99%

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Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

Olek

2020

Acta Geotech.

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Consolidation rate has significant influence on the settlement of structures founded on soft fine-grained soil. This paper presents the results of a series of small-scale and large-scale Rowe cell consolidation tests with pore water pressure measurements to investigate the factors affecting the consolidation process. Permeability and creep/resistance structure factors were considered as the governing factors. Intact and reconstituted marine clay from the Polish Carpathian Foredeep basin as well as clay-sand mixtures was examined in the present study. The fundamental relationship correlating consolidation degrees based on compression and pore water pressure was assessed to indicate the nonlinear soil behaviour. It was observed that the instantaneous consolidation parameters vary as the process progresses. The instantaneous coefficient of consolidation first drastically increases or decreases with increase in the degree of consolidation and stabilises in the middle stage of the consolidation; it then decreases significantly due to viscoplastic effects occurring in the soil structure. Based on the characteristics of the relationship between coefficient of consolidation and degree of dissipation at the base, the consolidation range that complies with theoretical assumptions was established. Furthermore, the influence of coarser fraction in clay-sand mixtures in controlling the consolidation rates is discussed. Keywords Clays Á Consolidation Á Data optimisation Á Excess pore water dissipation Á Gradient-based algorithm Á Permeability List of symbols CA Casagrande method c v Coefficient of consolidation c v e Instantaneous coefficient of consolidation based on compression c v u & Bartłomiej Szczepan Olek

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Section: Predominant Factors Controlling the Rate Of Volume Changementioning

confidence: 99%

Section: Optimisation Msl Consolidation Testsmentioning

confidence: 99%

Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

Olek

2020

Acta Geotech.

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“…The readings of the dial gauge, the time recorded, and the coeffi- The coefficient of consolidation can be calculated according to Eq. 5 (Olek 2019): where C v is the coefficient of consolidation, cm 2 /s; h represents the maximum drainage distance equal to a half of the average value of the initial and end heights of the samples at a certain level of pressure, cm; and t 90 is the time required for the consolidation degree reached 90%, s. According to the above Eq. 5, the coefficient of consolidation for the control group, PAM+PAC+lime (A), PAM+lime (B), PAM+PSAF+lime (C), PAM+PSAF (D), PAM (E), and PAM+PAC (F), is calculated, and the calculation results are shown in Table 7.…”

Section: Coefficient Of Consolidationmentioning

confidence: 99%

Performance of river sediments after flocculation-pressure filter membrane-vacuum preloading

Sun

Zheng

2020

Environ Sci Pollut Res

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The main problem in the reduction of river bottom sediments is to solve the dewatering of the sludge. The commonly used natural air drying method requires a large amount of time and economic cost. In this paper, different treatments were developed for the needs of the project, and related tests were carried out on the reduction of the sludge. Firstly, two or more flocculants were compounded according to the nature of the sludge. The 6 different treatments were determined according to the sedimentation and the turbidity value of the supernatant. Secondly, the dewatering test was carried out on river sediments after flocculationvacuum preloading. The dewatering effect of different flocculants, water quality, dissipation of pore water pressure, vane shear strength, compression coefficient, and coefficient of consolidation have been analyzed after flocculation-vacuum preloading. The polysilicate aluminium ferric (PSAF) can greatly increase the dewatering efficiency of the filter press membrane, and the final dewatering amount could reach 310 g. The effect of purifying water quality was PSAF>PAM (polyacrylamide, PAM-1(18 million): PAM-2(23 million) = 3:7)>PAC (polyaluminium chloride). The PSAF and PAC could increase the pH of the water during the vacuum preloading test. The PAM has the best the vane shear strength. Lime could improve the vacuum preloading and the vane shear strength when it was added to other flocculants. The incorporation of PSAF could accelerate the dissipation and increase the final dissipation value of pores water pressure. Compared with PAM+PAC+lime, PAM+lime, PAM+PSAF+ lime, PAM+PSAF, and PAM+PAC, the overall effect and price of the PAM is optimal.

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“…From the practical point of view, each 'conventional method' does not give unambiguous and reliable results and is even difficult to apply due to the presence of initial and secondary compression and/or data scattering [6]. Several full-matching approaches have been proposed and verified based on the experimental studies [7][8][9][10][11] to overcome reported issues. In the full-matching approaches all the recorded measurements are utilised and reflects the whole consolidation process.…”

Section: Introductionmentioning

confidence: 99%

Archives of Civil Engineering

Olek

2022

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The pattern of pore water pressure dissipation from the one-dimensional consolidation test significantly affects the calculated value of the coefficient of consolidation. This paper discusses the interpretation methodology for laboratory dissipation data from the oedometer test with the pore water pressure measurements or Rowe cell test. In the analysis, the gradient-based algorithm for finding the optimal value of the coefficient of consolidation is used against experimental results, obtained for various fine-grained soils. The appropriate value of coefficient of consolidation is considered as one with the lowest associated error function, which evaluates fitness between the experimental and theoretical dissipation curves. Based on the experimental results, two different patterns of the pore water pressure dissipation are identified, and the saturation of the specimen was found to be the key factor in describing the change in the patterns. For the monotonically decreasing dissipation curve, an inflection point is identified. The values of degree of dissipation at the inflection point are close to the theoretical value of 53.4%.

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Critical Reappraisal of Casagrande and Taylor Methods for Coefficient of Consolidation

Cited by 7 publications

References 29 publications

Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

Performance of river sediments after flocculation-pressure filter membrane-vacuum preloading

Archives of Civil Engineering

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