The permeability of natural soft clays. Part I: Methods of laboratory measurement

1983 ◽  
Vol 20 (4) ◽  
pp. 629-644 ◽  
Author(s):  
F. Tavenas ◽  
P. Leblond ◽  
P. Jean ◽  
S. Leroueil
Keyword(s):  
Laboratory Tests ◽  
Stress Conditions ◽  
Laboratory Measurement ◽  
Test Equipment ◽  
Large Specimen ◽  
Soft Clays ◽  
Field Stress ◽  
Constant Rate ◽  
Natural Clays ◽  
Constant Head

The methods of measuring the permeability of clays in the laboratory are investigated. Constant head tests in the triaxial are best suited for testing large specimen under field stress conditions provided the cell is modified to eliminate leakage. Using this type of test, the validity of Darcy's law is confirmed.Falling head tests in the oedometer are very simple to perform and subject to minimal sources of errors. However, small size specimens may not be totally representative.Indirect evaluations of the permeability from consolidation tests are shown to be unreliable particularly in structured natural clays: evaluation of k from cv measurements in step-loaded tests gives much too low values, constant rate of strain tests strongly overestimate k in the vicinity of σp′ and give nonrepresentative e vs. lg k relations; controlled gradient tests tend to underestimate k at all void ratios. Keywords: permeability, clays, laboratory tests, test equipment, consolidation tests.

Evaluation of a compacted till liner test pad constructed over a granular subliner contingency layer

1993 ◽  
Vol 30 (4) ◽  
pp. 667-689 ◽  
Author(s):  
R. Kerry Rowe ◽  
Chris J. Caers ◽  
Cliff Chan
Keyword(s):  
Hydraulic Conductivity ◽  
Laboratory Tests ◽  
Visual Inspection ◽  
Field Performance ◽  
Friction Angle ◽  
Stress Conditions ◽  
Clay Liners ◽  
Liner Material ◽  
Field Stress ◽  
Block Sampling

The construction and evaluation of a compacted clayey till test pad constructed over a stone layer are described. The evaluation of the clayey liner involved (i) excavation of six test pits through the liner, followed by careful visual inspection for defects in the liner; (ii) sampling of the liner using standard 75 mm diameter Shelby tubes, a 150 mm diameter piston sampler, and block sampling; (iii) triaxial hydraulic conductivity tests on samples of liner material consolidated to a number of stress levels relevant to the proposed design; and (iv) diffusion tests on samples of liner material. Based on the results it is concluded that it was possible to construct a low-permeability liner (hydraulic conductivity less than 1.4 × 10−8 cm/s under expected field stress conditions). Geotextiles from above and below the compacted liner were carefully exhumed and subjected to a series of laboratory tests to examine (i) the effect of construction damage on the geotextile's strength; (ii) the effectiveness of the geotextile to minimize intrusion of the clay liner through the geotextile and into the stone layer(s) under expected field stress conditions; (iii) the effectiveness of the geotextile as a filter for the compacted liner material under high upward gradient conditions; and (iv) the friction angle between the geotextile and clay, and geotextile and stone. The geotextiles exhumed from the test liner showed some evidence of construction damage; however, based on the field observations and subsequent laboratory tests, it is concluded that they performed adequately. Key words : waste disposal, clay liners, geotextiles, field performance, hydraulic conductivity, landfills.

Hydraulic tomography using joint inversion of head and flux data 

2021 ◽  
Author(s):  
Behzad Pouladiborj ◽  
Olivier Bour ◽  
Niklas Linde ◽  
Laurent Longuevergne
Keyword(s):  
Hydraulic Conductivity ◽  
Joint Inversion ◽  
Data Type ◽  
Data Types ◽  
Hydraulic Tomography ◽  
Flux Data ◽  
Planning And Design ◽  
Constant Rate ◽  
Resolution Analysis ◽  
Constant Head

<p>Hydraulic tomography is a state of the art method for inferring hydraulic conductivity fields using head data. Here, a numerical model is used to simulate a steady-state hydraulic tomography experiment by assuming a Gaussian hydraulic conductivity field (also constant storativity) and generating the head and flux data in different observation points. We employed geostatistical inversion using head and flux data individually and jointly to better understand the relative merits of each data type. For the typical case of a small number of observation points, we find that flux data provide a better resolved hydraulic conductivity field compared to head data when considering data with similar signal-to-noise ratios. In the case of a high number of observation points, we find the estimated fields to be of similar quality regardless of the data type. A resolution analysis for a small number of observations reveals that head data averages over a broader region than flux data, and flux data can better resolve the hydraulic conductivity field than head data. The inversions' performance depends on borehole boundary conditions, with the best performing setting for flux data and head data are constant head and constant rate, respectively. However, the joint inversion results of both data types are insensitive to the borehole boundary type. Considering the same number of observations, the joint inversion of head and flux data does not offer advantages over individual inversions. By increasing the hydraulic conductivity field variance, we find that the resulting increased non-linearity makes it more challenging to recover high-quality estimates of the reference hydraulic conductivity field. Our findings would be useful for future planning and design of hydraulic tomography tests comprising the flux and head data.</p>

scholarly journals Research on Horizontal Coefficient of Consolidation of Vietnam’s Soft Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Nu Nguyen Thi ◽  
Bui Truong Son ◽  
Do Minh Ngoc
Keyword(s):  
Experimental Study ◽  
Laboratory Tests ◽  
Soft Soil ◽  
Coefficient Of Consolidation ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Constant Rate ◽  
Different Types ◽  
Cell Test ◽  
Dissipation Test

The horizontal coefficient of consolidation is the most important parameter for designing the improvement of soil soft by prefabricated vertical drains (PVDs) combined with surcharge and vacuum preloading. This paper presents the experimental study on the horizontal coefficient of consolidation (ch) of some soft soils distributed in Vietnam. The ch value was determined by the laboratory test and CPTu dissipation test. The laboratory tests included the Rowe consolidation cell test and constant rate of strain consolidation with radial drainage test. Two types of consolidation laboratory tests were performed. The experimental results indicated that the ch value is always larger than the vertical coefficient of consolidation of soil (cv). The ratio of ch/cv depends on the consolidated pressure, type of soil, and the anisotropy of soil. The ratio of ch/cv is different in different types of soft soil in Vietnam. In the normally consolidated state, the ch/cv ratio ranges from 1.35 to 10.59. It was necessary to choose the ch value at the consolidated stress level for calculating the PVD spacing.

scholarly journals FLOATING SIPHON WITH A CONSTANT HEAD

1974 ◽  
Vol 5 (2) ◽  
pp. 98-107
Author(s):  
RICHARD THOMSEN
Keyword(s):  
Water Level ◽  
Water Surface ◽  
Surface Registration ◽  
Registration System ◽  
Outlet Tube ◽  
Discharge Water ◽  
Constant Rate ◽  
Constant Head ◽  
Better Than

A floating siphon made up of concentric tubes is proposed as a reliable and inexpensive device to discharge water from a reservoir tank at a constant rate independent of the water level in the tank, provided the siphon is discharged freely into the atmosphere. By adjusting the opening area in the outlet tube continuously, any constant discharge can be obtained. With simple aids the siphon has been calibrated to work with an accuracy better than 5 ‰. By means of an electric Water Surface Registration System it is proved that the variation in discharge is better than 1 ‰ at a discharge of 0.3–2.4 1/s.

scholarly journals Back-Calculation of Element Tests with a Rate Dependent Soft Soil Model

2016 ◽  
Author(s):  
Jorge Yannie ◽  
Nallathamby Sivasithamparam
Keyword(s):  
Laboratory Tests ◽  
Soft Soil ◽  
Laboratory Data ◽  
Rate Dependency ◽  
Soft Clays ◽  
Rate Dependent ◽  
Soil Model ◽  
Back Calculation ◽  
Complex Boundary ◽  
Selection Of

It is well known that soft clays are geo-materials with properties such as fabric, bonding and rate-dependency. The response observed when modelling complex boundary value problems will depend on the ability of the soil model to capture these features. This paper point out the importance of modelling anisotropy, de-structuration and rate-dependency for normally or slightly over-consolidated clays. In this study, samples from Bothkennar clay (Scotland) were simulated and compared to laboratory data. The constitutive model used in this paper is the recently developed Creep- SCLAY1S. The model could predict both qualitative and quantitative the tests results. Selection of the parameters from standard laboratory tests was a key step in the predictions. It was relevant to have different types of laboratory tests to derive a best set of parameters.

scholarly journals ANALISIS PERBANDINGAN NILAI KOEFISIEN PERMEABILITAS TANAH UJI LAPANGAN DAN UJI LABORATORIUM

2020 ◽  
Vol 3 (1) ◽  
pp. 97
Author(s):  
Philip Chen ◽  
Gregorius Sandjadja Sentosa
Keyword(s):  
Initial Data ◽  
Permeability Coefficient ◽  
Laboratory Tests ◽  
Pumping Test ◽  
Soil Permeability ◽  
Pumping Tests ◽  
Final Project ◽  
Coefficient Of Permeability ◽  
The Difference ◽  
Constant Head

The coefficient of permeability (k) results of pumping tests are used as initial data to determine the rate of water seepage in the soil, determining the permeability capability of the soil can be done by measurements in the laboratory and in the field. In reality the permeability coefficient value of field test is not the same as the test in the laboratory. This final project will analyze the difference in value (k) obtained from field and laboratory tests in order to enrich the data in determining the value of permeability coefficient (k). The analysis uses Thiem and Theis method in analyzing the results of pumping tests. And using constant head permeameter to determine the value of the coefficient of permeability (k) in laboratory. From the analysis results obtained by the Thiem method, the permeability coefficient (k) obtained is in the range of  6,8x cm/sec - 2,8x cm/sec, and Theis method is obtained in the range of  6,03x cm/sec - 6,03x cm/sec. Meanwhile the results of the coefficient of soil permeability (k) by the laboratory tests using the constant head permeameter is in the range 1,43x  cm/sec - 8,76x cm/sec. And for calculations using the Hazen method the result is in the range 8,71x cm/sec - 4,35x cm/sec.AbstrakNilai koefisien permeabilitas (k) hasil pumping test digunakan sebagai data awal untuk mengetahui kecepatan rembesan air di dalam tanah, penentuan kemampuan permeabilitas tanah dapat dilakukan dengan pengukuran di laboratorium dan di lapangan. Dalam kenyataannya nilai koefisien permeabilitas uji lapangan biasanya tidak sama dengan uji di laboratorium. Penelitian ini akan menganalisa perbedaan nilai (k) yang didapat dari uji lapangan dan uji laboratorium guna memperkaya data dalam menentukan nikai koefisien permeabilitas (k). Analisa pada penelitian ini menggunakan metode Thiem dan metode Theis dalam menganalisa hasil pumping test pada lapangan. Dan menggunakan constant head permeameter sebagai alat menentukan nilai koefisien permeabilitas (k) pada laboratorium. Serta menggunakan metode rumus empiris Hazen untuk menentukan nilai koefisien permeabilitas (k) berdasarkan ukuran butiran. Dari hasil analisis yang diperoleh dengan metode Thiem nilai koefisien permeabilitas (k) yang didapat berada pada rentang  6,8x m/detik - 2,8x cm/detik, dan dengan metode Theis didapat pada rentang 6,03x cm/detik - 6,03x cm/detik. Sedangkan hasil uji laboratorium menggunakan permeameter constant head mendapatkan hasil nilai koefisien permeabilitas tanah (k) pada rentang 1,43x  cm/detik  -   8,76x cm/detik. Dan didapat hasil 8,71x cm/detik - 4,35x cm/detik untuk perhitungan menggunakan metode Hazen.

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