The effects of electroosmotic field treatment on the soil properties of a soft sensitive clay

1991 ◽  
Vol 28 (6) ◽  
pp. 763-770 ◽  
Author(s):  
K. Y. Lo ◽  
K. S. Ho
Keyword(s):  
Soil Properties ◽  
Ph Value ◽  
Soft Clay ◽  
Triaxial Tests ◽  
Carbonate Content ◽  
Failure Envelope ◽  
Effective Stresses ◽  
Copper Electrodes ◽  
Preconsolidation Pressure ◽  
Sensitive Clay

A field test was undertaken to assess the effectiveness of the electroosmotic strengthening of the soft sensitive (Champlain Sea) clay in the Gloucester Test Fill site by using specially designed copper electrodes to improve treatment efficiency. Tube samples, 127 mm in diameter, were recovered before and after field treatment for detailed laboratory tests. Isotropically consolidated undrained triaxial tests with pore-pressure measurements were performed. It was found that the failure envelope after treatment was significantly higher than the initial envelope, indicating that the strength in terms of effective stresses increased. Consolidation tests showed that, as a result of treatment, the preconsolidation pressure increased from 53 to 98 kPa. The soft clay is virtually "overconsolidated" by the process. Additional effects of electroosmosis on the properties of the soft clay are the increase in plasticity, carbonate content, and salinity and the decrease in sensitivity. There is, therefore, a general improvement in soil properties after treatment, both in terms of total and effective stresses. Key words: electroosmosis, soft sensitive clay, failure envelope, sensitivity, preconsolidation pressure, pH value.

Settlement of Mat Foundation on Thick Stratum of Sensitive Clay

1965 ◽  
Vol 2 (4) ◽  
pp. 299-312 ◽  
Author(s):  
L Casagrande ◽  
P Firing ◽  
G Schoof ◽  
E John Tttrcke
Keyword(s):  
Groundwater Level ◽  
Industrial Plant ◽  
Effective Stresses ◽  
Preconsolidation Pressure ◽  
Load Increase ◽  
Order Of Magnitude ◽  
Mat Foundation ◽  
Building Load ◽  
Sensitive Clay ◽  
Thick Stratum

Foundation investigations for an industrial plant on a thick stratum of preconsolidated, sensitive clay are presented. In spite of the fact that the effective stresses in the clay caused by the building load remained below the average preconsolidation pressure of the clay, the settlement of the buildings locally appreciably exceeded the anticipated order of magnitude. It is shown that a drop in the groundwater level by a few feet would result in the effective stresses exceeding the preconsolidation pressure within the upper portion of the clay stratum. With such an assumption, the consolidation would not be governed by the very flat recompression branch of the consolidation curve, but in part also by the steep virgin compression branch of the consolidation curve. It is concluded that, when dealing with preconsolidated, sensitive clays, the total effective stresses caused by a proposed structure should be kept within a safe margin below the average preconsolidation pressure in order to make provision for any unforeseen load increase such as might arise from a drop in the groundwater elevation.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

Electroosmotic strengthening of soft sensitive clays

1991 ◽  
Vol 28 (1) ◽  
pp. 62-73 ◽  
Author(s):  
K. Y. Lo ◽  
I. I. Inculet ◽  
K. S. Ho
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Strength Increase ◽  
Sample Length ◽  
Voltage Distribution ◽  
Steady Current ◽  
Preconsolidation Pressure ◽  
Sensitive Clay ◽  
Pressure Stress

A comprehensive experimental investigation on the electroosmotic strengthening of soft sensitive clay was performed to assess the effectiveness of the treatment and to study the mechanism of the process. A specially designed electroosmotic cell was developed to prevent gas accumulation near the electrodes, to allow better electrode-soil contact, and to improve the treatment efficiency. This apparatus also enables the monitoring of the generated negative pore-water pressure along the sample length, settlement, voltage distribution, and current variation during treatment. The investigation covered two different types of soil trimmed at different orientations: the vertically and horizontally trimmed overconsolidated Wallaceburg clay and the vertically trimmed slightly overconsolidated soft sensitive Gloucester (Leda) clay. Results of this study showed that the voltage distribution and induced negative pore pressure at equilibrium along the sample are linear with steady current flow across the sample, indicating that the electrode design in the electroosmosis test apparatus is efficient. The electroosmotic consolidation curve is similar to that of the conventional consolidation curve, and the preconsolidation pressure was increased by 51–88% with an applied voltage up to 6 V. The undrained shear strength increased to a maximum of 172%, and the moisture content decreased by 30%. The technique of electrode reversal is employed, and a relatively uniform strength increase between the electrodes is observed. Key words: electroosmosis, electroosmotic cell, soft sensitive clay, negative pore-water pressure, preconsolidation pressure, stress–strain behaviour.

A Change of Undrain Shear Strength of Soft Ground during Consolidation Process

2014 ◽  
Vol 513-517 ◽  
pp. 269-272
Author(s):  
Yeong Mog Park ◽  
Ik Joo Um ◽  
Norihiko Miura ◽  
Seung Cheol Baek
Keyword(s):  
Shear Strength ◽  
Soft Clay ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Test Results ◽  
Exponential Equation ◽  
Consolidation Process ◽  
Degree Of Consolidation ◽  
Clay Ground ◽  
Strength Increment

The purpose of this study is to investigate the undrain shear strength increment during consolidation process of soft clayey soils. Thirty kinds of laboratory triaxial tests have been performed using undisturbed and remolded Ariake clay samples with different degree of consolidation and 5 kinds of confining pressure. Test results show that well known linear equation proposed by Yamanouchi et al.(1982) is overestimated the strength of undisturbed soft clay ground in the process of consolidation. A new simple and reasonable exponential equation proposed in this paper.

scholarly journals Classification of brown earths based on field and laboratory properties: Problematic issues and proposition of their solution

2019 ◽  
Vol 52 (2) ◽  
pp. 225
Author(s):  
Karolina Woźnica ◽  
Agnieszka Józefowska ◽  
Justyna Sokołowska ◽  
Ryszard Mazurek ◽  
Tomasz Zaleski
Keyword(s):  
Calcium Carbonate ◽  
Main Parameter ◽  
Ph Value ◽  
Soil Classification ◽  
Base Saturation ◽  
Carbonate Content ◽  
Field Guide ◽  
Content Determination

<p class="Default">In this paper, the current problems associated with the classification of brown earths, are presented. According to the Polish Soil Classification (PSC) (1989, 2011), base saturation is the main parameter for identifying eutrophic and dystrophic brown soils. In practice, however, it is not possible to determine the base saturation value in the field. Therefore, the aim of this study was to estimate the base saturation using a regression equation and create a field guide for brown earths, based on the pH value, measured using a Hellige indicator, and the calcium carbonate content. Determination of the pH ranges enabled the classification of brown earth types in the field. These results suggest that pH can be used as a proxy for base saturation especially in the field. A change in the hierarchy of soil (sub)types is proposed for the new Polish Soil Classification.</p>

scholarly journals PASSAGE OF WHEAT FIRE IMPACT ON SOIL PROPERTIES AND ENVIRONMENT IN KURDISTAN REGION

2021 ◽  
Vol 52 (2) ◽  
pp. 461-470
Author(s):  
Tariq & et al.
Keyword(s):  
Soil Properties ◽  
Ph Value ◽  
Fire Severity ◽  
Chemical Properties ◽  
Field Capacity ◽  
Infiltration Rate ◽  
Germination Percentage ◽  
Biological Properties ◽  
Surface Burn ◽  
Effect Of Surface

The study was conducted to examine the effect of surface burn severity (Moderate, Severe and Unburned) of wheat straw on soil properties. The results showed statistical differences in some soil physical, chemical and biological properties. Bulk density and field capacity increased statistically by the severity of fire; however, porosity and infiltration rate were statistically lower in sever burned plot when compared to unburned plot. The chemical properties, soil organic matter (SOM), P, Ca, S, Cl, K, Mo, Fe and As were not affected by the fire. The pH value was increased slightly by increasing the fire severity, while, EC was decreased when compared with the unburned plot. It was found a statistical reduction in the number of bacterial and fungal cells per gram soil in the burned plots. A moderate and severe fire reduced seed germination percentage significantly. This finding suggests that fire severity may destruct the biological, physical and some of the chemical properties of the soil, and this may impact negatively on plant growth in the next growing season.

Experience with Interface Shear Box Testing for Pipe-Soil Interaction Assessment on Sand

2021 ◽  
Author(s):  
Zack Westgate ◽  
Ricardo Argiolas ◽  
Regis Wallerand ◽  
Jean-Christophe Ballard
Keyword(s):  
Soil Properties ◽  
Normal Stress ◽  
Oil And Gas ◽  
Early Stage ◽  
Soft Clay ◽  
Interface Roughness ◽  
Coarse Grained ◽  
Interface Shear ◽  
Shear Box ◽  
Test Database

Abstract This paper is a companion paper to OTC 28671, titled "Experience with Interface Shear Box Testing for Axial Pipe-Soil Interaction Assessment on Soft Clay", and presents a similar range of experience and best practice recommendations for geotechnical laboratory testing to determine soil properties relevant to pipeline-seabed friction on sandy seabeds. The paper is underpinned by a new database that demonstrates the driving parameters that influence interface friction in granular materials. By accurately quantifying shear resistance along the pipe-soil interface under low normal stresses imposed by subsea pipelines, design ranges in friction can be narrowed and/or tailored to specific pipeline conditions. These improved geotechnical inputs to pipe-soil interaction can alleviate unnecessary axial expansion mitigation and lateral stabilization measures, unlocking cost savings otherwise unavailable through conventional testing. A large database is presented, compiled from both previously published research and unpublished recent industry experience with low normal stress interface shear testing using various modified direct shear box devices. The test database comprises several coarse-grained soil types of both silica and carbonate minerology tested against pipeline coatings of various material, hardness and roughness. The database populates a framework for assessing frictional pipe-soil interaction response, illuminating key trends from normal stress, interface roughness and hardness, and particle angularity, which otherwise remain elusive when examined through individual test datasets. This database and the populated framework provides guidance to pipeline and geotechnical engineers in the form of a basis for initial estimates of axial and lateral friction of pipelines on sand and an approach for improving these estimates via focused site-specific testing. The test database includes previously unreleased project data collected over the past few years for offshore oil and gas projects. Similar to its predecessor paper on soft clays (OTC 28671), this paper shares the authors’ collective experience providing guidance on the planning, execution and interpretation of low stress interface shear tests in sands. The combined databases across both papers provide a significant improvement in early stage guidance for characterization of geotechnical soil properties for subsea pipeline design.

scholarly journals Analysis of Undrained Seismic Behavior of Shallow Tunnels in Soft Clay Using Nonlinear Kinematic Hardening Model

2020 ◽  
Vol 10 (8) ◽  
pp. 2834
Author(s):  
Mohsen Saleh Asheghabadi ◽  
Xiaohui Cheng
Keyword(s):  
Finite Element ◽  
Kinematic Hardening ◽  
Soft Clay ◽  
Hysteresis Loops ◽  
Stiffness Degradation ◽  
Triaxial Tests ◽  
Embedment Depth ◽  
Ground Acceleration ◽  
Cyclic Shear ◽  
Hardening Model

In this study, a soil–tunnel model for clay under earthquake loading is analyzed, using finite element methods and a kinematic hardening model with the Von Mises failure criterion. The results are compared with those from the linear elastic–perfectly plastic Mohr–Coulomb model. The latter model does not consider the stiffness degradation caused by imposing cyclic loading and unloading to the soil, whereas the kinematic hardening model can simulate this stiffness degradation. The parameters of the kinematic hardening model are calibrated based on the results of experimental cyclic tests and finite element simulation. Here, two methods—one using data from cyclic shear tests, and the other a new method using undrained cyclic triaxial tests—are used to calibrate the parameters. The parameters investigated are the peak ground acceleration (PGA), tunnel lining thickness, tunnel shape, and tunnel embedment depth, all of which have an effect on the resistance of the shallow tunnel to the stresses and deformations caused by the surrounding clay soils. The results show that unlike traditional models, the nonlinear kinematic hardening model can predict the response reasonably well, and it is able to create the hysteresis loops and consider the soil stiffness degradation under the seismic loads.

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