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Parasitic Head Losses During Laboratory Permeability Tests
Parasitic head losses incurred outside the tested soil specimen may alter the results of laboratory permeability tests. They can be measured by running a blank test in an empty permeameter, and determining the flow resistance of the testing equipment. They can also be assessed by using the difference between a constant-head test, where the hydraulic heads are measured within the tested specimen, and a variable-head test, where the hydraulic heads are measured outside the specimen and include the parasitic head losses of the testing equipment. When not accounted for, they can lead to permeability values that are underestimated. An electric analog provides an analytical relationship between variable- and constant-head test results. The parameters in the analytical solution can be obtained via blank permeability tests. This article emphasizes the need to measure hydraulic heads inside the soil specimen during laboratory permeability tests.
Practical Considerations when Using the Swedish Fall Cone
This paper presents the results of Swedish fall cone tests and Casagrande liquid limit tests conducted on saline Champlain Sea clay samples from Lachenaie, Quebec. The main objective was to study a few hitherto unanswered practical questions regarding these testing methods. Penetration range is found to affect the Hansbo's relationship used in fall cone experiments, while the mass and the bluntness degree of the cone have no effect on it. A direct relationship between thixotropic regain in shear strength and sensitivity is found. When measuring the liquid limit, if only the first penetration depth is recorded, results are up to 5 % smaller than those obtained when following the standard proc...
Water-Retention Curves of Coarse Soils Without Organic Matter
It is difficult to obtain a reliable water-retention curve (WRC) for coarse-grained soils without organic matter. As a result, the field behavior of draining layers in engineering problems may be poorly predicted. The main goal of this paper is to develop predictive methods for the WRC of coarse-grained soils based on long-column, long-duration drainage test data and available soil properties. The paper first shows that predictive models perform poorly for coarse-grained soils, but four descriptive models can correctly fit the test data. Second, it provides predictive equations for the air-entry value (AEV), residual suction ur, and residual water content ?r as simple functions of the effective size d10 and void ratio e. Third, it provides new formulas that relate d10 and e to the parameters of descriptive models; thus, enabling them to become very simple to use predictive models for ed10 > 0.05 mm. The paper finally shows that small variations in d10 and e have more influence on the saturated permeability than on the WRC parameters.
Permeability Test Results With Packed Spheres and Non-Plastic Soils
This paper examines permeability test results with packed spheres and non-plastic soils. Most tests on packed spheres were performed in physics and chemistry, using liquids or gases to measure the intrinsic permeability, K (m2). All K (m2) were converted into saturated hydraulic conductivity ksat (m/s). Equal spheres and spheres having a unimodal or multimodal grain size distribution curve (GSDC) were tested. We point out interesting differences between the approaches in physics, geotechnique, and hydrogeology, then discuss difficulties with testing methods, before analyzing all test data. We propose a method to fit a GSDC with either a single, or a sum of lognormal equations, which gives a ...
Performance of Fully Grouted Piezometers Under Transient Flow Conditions: Field Study and Numerical Results
Piezometers can be installed in clay layers using the fully grouted method. This method is said to reduce installation costs and facilitate installation, especially for nested piezometers. The success of a fully grouted installation depends upon the ratio of grout and surrounding soil hydraulic conductivity and upon the grout physical stability. This article presents new results from field tests and numerical simulations regarding the performance of fully grouted piezometers under transient flow conditions. The field observations show that using low-permeability grout for piezometer installation provides precise pore water pressure (PWP) measurements. This confirms previous findings on the fully grouted installation technique. Field observations for a very high-permeability grout that could be more than 1,100 times more permeable than the soil result in PWPs that totally differ from the PWP obtained with a low-permeability grout. Using three scenarios involving transient flow, the numerical results show that hydraulic conductivity ratios between 0.001 and 10 provide an accurate pore pressure response without a significant time lag for soils with a very low permeability (K
The Lifeline of the Oregon Country
In The Lifeline of the Oregon Country, James Gibson compellingly immerses the reader in one of the most intractable problems faced by the Hudson's Bay Company: how to realize wealth from such a remote and formidable land. The personalities, places, obstacles, and operations involved in the brigade system are all described in fascinating detail, stretch by stretch from Fort St. James, the depot of New Caledonia on the upper reaches of the Fraser River, to Fort Vancouver, the Columbia Department’s entrepôt on the lower Columbia River, and back. Never before has such a rich collection of primary information concerning the fur trade supply system and the constraining role of logistics been so meticulously assembled. The Lifeline of the Oregon Country will prove indispensable to historians, researchers, and fur trade enthusiasts alike, and is an important contribution to our understanding of the economic history of the Pacific Slope.
