Standard Oedometer Tests Research Articles

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Alkali contamination induces swelling in the inherently non-swelling soils, resulting in heave severely damaging the sub and superstructures. Stabilization measures must be taken in vulnerable areas to prevent such colossal losses. Considerable research has been conducted regarding the swelling behavior of soils contaminated with alkalis and the impact of subsequent stabilization techniques utilizing different industrial byproducts and pozzolanic materials. However, there is a paucity of such studies on the Red Earth (RE) of the Visakhapatnam region. Furthermore, limited attention was given to the effects of extremely low concentrations of alkalis on the swelling behavior of soils. RE in the study area of the Visakhapatnam region predominantly consists of quartz, kaolinite, and hematite. In phase 1 of the experimental analysis, RE was contaminated with a highly dilute NaOH solution (0.05 N), and the resulting swell characteristics were investigated. A free swell of 10% was observed. One-dimensional standard oedometer tests revealed an equilibrium swelling of 5.6%, indicating significant potential for substantial heave and subsequent damage. X-ray diffraction (XRD) analysis revealed the formation of natrolite and analcime zeolites with a hollow structure, which caused the swell. Peaks of silicate minerals like paragonite and ussingite were also observed, indicating the dissolution of authigenic minerals and new precipitations even at lower concentrations of NaOH. In phase 2, swell tests were conducted on a mixture of contaminated red earth (50% w/w), fly ash (25% w/w), and ground granulated blast furnace slag (GGBS, 25% w/w), and it was observed that the swelling was completely arrested. XRD analysis unveiled that even though siliceous zeolites were formed, the development of chrysotile, attapulgite, tobermorite, and dicalcium silicate effectively inhibited the swelling with their pozzolanic behavior.

Analysis of long-term settlement of road embankment on peat ground during its service period

Roads on peat grounds are subject to stringent requirements in terms of controlling the residual settlement during their service period in order to minimize the post-construction maintenance work. This paper addresses the applicability of the Finite Element Method (FEM) by incorporating a time-dependent model for peats to an evaluation of the residual settlement. The applicability of isotach viscoplasticity, used to describe the peats’ behavior under variable-rate compression, was confirmed in laboratory tests. Long-term consolidation test results and a model simulation revealed the particular importance of two mechanisms in the residual settlement in peat grounds, namely, the stress-dependency of the coefficient of consolidation, cv, and the viscosity-induced secondary consolidation. A model peat ground, capturing these mechanisms, was implemented for the FEM and applied to a case history of a high-standard road construction in Hokkaido, Japan. The viscoplastic parameters determined from standard oedometer tests successfully reproduced the observed long-term settlement in a peat-dominated section of the expressway. The analysis was extended to address the settlement in the peat ground with the installation of prefabricated vertical drains (PVDs). The results indicate that the delayed primary consolidation due to the stress-induced cv reduction can be significantly alleviated, while the settlement arising from the secondary consolidation over a longer term is little affected by the PVDs. These insights point to the importance of untangling the two mechanisms of long-term settlement for the sake of making accurate predictions of the residual settlement in different time scales.

Geotechnical investigation of the Naval dry dock at the Mietsu Naval Facility World Heritage Site, Japan

The Mietsu Naval Facility was established as a Western-style military facility by the Saga Clan in 1858. A geotechnical investigation of the Mietsu Naval Dock (MND) at the Mietsu Naval Facility World Heritage Site was performed using portable cone penetration tests, unconfined compression tests with suction measurement, and standard oedometer tests. The pile length of the wooden frame structure was determined using pulse waves. The slope of the western wall consists of four layers, and straw soil bags were arranged for slope stabilization. The slope of the western wall during construction and under use was analyzed based on total and effective stresses, respectively, and was found to be stable. The wooden structure of the eastern wall consists of four stages and has a complex structure of pine wood with intact bark. The second and third-stage piles have anchorage structures with several horizontal elements linked to the first and second-stage piles. The number of the piles in the third-stage indicates that it plays a central structural role. Even though ship were repaired at the bottom of the dock, there is no evidence of ground improvement to prevent damage from ship loads. Because the amount of decrease in effective overburden pressure corresponded to the amount of excavated soil with the load of the Denryu-maru, which was repaired in this dry dock, it is possible that ground improvement for entry and repair of the ship was not needed. The results of this study are useful for the maintenance, management, and restoration of the MND remains.

Effect of pore fluid pH on the collapse behaviour and microstructural evolution of a loess

This study investigated the role of pore fluid pH in governing the microstructural characteristics of loess soil and its ultimate effect on collapse mechanisms. A series of standard oedometer tests was conducted to evaluate the impact of acidic and alkaline pore fluid pH on the collapse behaviour of loess. The microstructural characterisation of soil exposed to different values of pore fluid pH was done by performing microscopic analysis of specimens before and after oedometer tests. In addition, the obtained micrographs were processed using an image analysis tool in order to interpret the influence of different pore fluid pH interactions on the evolution of soil pore-size distribution characteristics. The results obtained in this study indicated that the pore fluid pH has significant effect on the structural stability of loess and on the evolution of pore-size distribution during consolidation and consequently, on its wetting-induced collapse behaviour.

Creep in Primary Consolidation with Rate of Loading Approach

The debate on creep in primary consolidation is analysed with a power law model following an approach in which creep is considered as rate of loading. According to this approach, primary consolidation is one type of rate of loading. To verify this approach, two types of tests, standard oedometer test and oedometer test with drainage prevented, are conducted on three types of soils (two from NGES and the other from Port of Guangzhou). The result: creep exponents obtained from two kinds of tests agree well with each other. Moreover, the approach is further validated by tracking, for over 80 years, the data from settlement of the case history San Jacinto Monument, which is inconsistent with data calculated from the classical method. In the end, procedure of this approach, with which long term settlement is predicted, is illustrated, and this approach is compared with the classical method.

Laboratory Study on the Effect of Water Cations’ Concentrations on the Bojnord Clay Consolidation Process

The initial consolidation settlement process of saturated cohesive soils has been one of the most important issues to geotechnical engineers especially in important and sensitive structures based which are located on saturated clay layer with high thickness. In dealing with initial consolidation settlement process and reducing its negative and destructive consequences, a number of solutions have been presented including but not limited to the implementation of horizontal and vertical sand drainages, pre-loading and dynamic compaction; limitations of these methods include the necessity of implementing them before construction of the project. Furthermore, if the underground water level goes lower than regarded values, no appropriate approach else than the overhead reduction approach has been provided. In present research, with addition of concentrations of 250, 750 and 1250 Mg/lit in saturated water, laboratory study of the changes in initial consolidation settlement process, were investigated by standard Oedometer test device upon the addition of different concentrations of the cations, dissolved in saturated water on cylindrical samples of Bojnord clay with 2cm in height and 7.5cm in diameter. Achieved results represent significant changes in quantities of initial consolidation settlement process upon adding a variety of dissolved cations in saturated water; The results show that application of cations including aluminum (Al+3), calcium (Ca+2), magnesium (Mg+2), sodium (Na+) and potassium (K+) with different concentrations changes the values of initial consolidation settlement values in appropriate with type and concentration of cations that the highest reduction of the initial consolidation settlement of Bojnord clay valued at 24.61% for the sample made with Al+3 cation with ionic concentration of 1250 Mg/lit.

A Study with a New Device on Compression Properties of Fine-Grained Reconstituted Soils

For the purpose of examining the settlement behavior of fine-grained soils, a sufficient number of one- and three-dimensional consolidation tests on ten different reconstituted soils were performed in the study. A three-dimensional consolidation test apparatus, which is considered to be a modified form of standard oedometer test apparatus and permits lateral strains to occur, was designed. The consolidation tests were carried out both with standard oedometer and with the new test device so that the effect of different displacement conditions on the test results could be compared. Oedometer tests, by using both the conventional one-dimensional and the new test apparatus, were also carried out with the purpose of understanding the effect of test apparatus on the results. According to the plasticity indexes of the samples, it was found that three-dimensional settlements were greater than one-dimensional settlements at the vertical pressures of 200–300 kPa and higher. The slopes of three-dimensional settlements’ curves were found to be steeper than those determined from standard oedometer curves at the pressures of over 150–200 kPa. When comparing the calculated compression moduli for each group of test results, it was found that the three-dimensional moduli values were 50–75 % of the one-dimensional moduli values. On all of the three-dimensional test results, performed, while the central part was being loaded incrementally, small settlements on the surrounding part were observed. During the removal of the applied loads from the central part, the small settlements reached on the surrounding part approximately remained constant.

One-dimensional consolidation of lime-treated dredged harbour sediments

Dunkirk marine sediments can be used as an alternative roadbed material, and a full-scale test road using this has been successfully built at Dunkirk harbour in France. In this context, the long-term deformation behaviour of Dunkirk sediments is of crucial importance in the evaluation of roadbed deformation. The standard oedometer tests were carried out to plot the e-logσ′ and e-logt curves, which were used to determine the compression index (Cc), swelling index (Cs) and coefficient of secondary compression Cα during loading and unloading. The effect of lime treatment on primary and secondary compression behaviour was investigated. The soil structure influences greatly the yield consolidation stress σy′, which is increased with lime content. Both σy′–ey (void ratio at σy′) and Cc–Cs relations are analysed. It is observed that σy′ is connected with ey by a power function and Cc/Cs varies between 0.013 and 0.1. Cα remains low at consolidation stress σ′ < σy′ and reaches a peak at σ′ = (1 – 4) σy′ followed by a decrease in Cα. Lime addition induces the peak Cα moving towards a larger consolidation stress of 5σy′. Based on the Cα–lg(t/tp) curves, it is interesting to note that t = 20tp (end-of-primary consolidation time) is suggested as a sufficient consolidation time to study the secondary compression behaviour of marine sediments. The Cα/Cc ratios of various clays including Dunkirk sediments show that Cα/Cc changes mainly in the range of 0.02–0.05. However, the Cα/Cc ratio is different for lime-treated sediments (Cα/Cc* = 0.0164) and untreated sediments (Cα/Cc* = 0.0432). Two separate zones in Cα–Cs* plot are clearly observed for untreated and treated sediments with boundary line of Cα = 0.0433Cs* – 0.0008.

Effect of lime treatment on geotechnical properties of Dunkirk sediments in France

The increasing cost associated with high-quality materials has lead to the need for sediments to be treated and then used in road construction in the context of durable development. Therefore, the modification and stabilisation of Dunkirk marine sediments by using lime is necessary to study for their potential use in road construction. Based on the physical characteristics of untreated sediments, a series of laboratory tests to investigate the geotechnical properties of untreated sediments and lime-treated sediments, such as unconfined compressive strength tests, standard oedometer tests, direct shear tests and triaxial tests, were performed. Lime was added in percentages of 3% and 6%, by weight of dry sediments. The test results show a significant improvement in unconfined compressive strength and shear strength due to the addition of lime. From the strain–stress relationship of compressive strength tests, it can be found that the failure mode of solidified sediments develops gradually from plastic failure to brittle failure, while the failure strength increases and the failure strain decreases with lime content. Compared with untreated sediments, the shear strength parameters of solidified sediments determined by direct shear tests, such as internal friction angle and cohesion, are increased owing to the pozzolanic reaction between lime and clay minerals. Using the oedometer apparatus, it is observed that after lime treatment, the preconsolidation pressure, the coefficient of consolidation and the compression index are increased, while the swelling index is decreased. The characteristics of the deviator stress–axial strain relation and the pore water pressure distribution under different confining stresses are compared with untreated and treated sediments, and the effect of lime content on cohesion and internal friction angle determined by triaxial tests is discussed.

Settlement Control of Soft Ground using Cement-Ricehusk Stabilization

Cement is widely used for improvement of soft soils, but financial and environmental concerns are causing genuine concerns to all parties, leading to the quest for alternative and effective stabilizers. Ricehusk is an agricultural waste in Malaysia, commonly disposed of by open burning or dumping in landfills. Considering that the ashes derived from ricehusk are pozzolanic in nature, there is a possibility that a cement-ricehusk mixture could effectively improve soft soils with reduced cement dosage. This study examines the mixture’s effectiveness by monitoring the settlement reduction in a clay soil. Standard oedometer tests were carried out on a soft marine clay sample admixed with cement-ricehusk. Test specimens contained 0-10% cement and 0-5% of ricehusk respectively, and were left to cure for either seven or 28 days. The stabilized specimens were observed to undergo significant reduction in compressibility, verifying the potential of cement-ricehusk as an alternative soft soil stabilizer.

Engineered use of microbial gas production to decrease primary consolidation settlement in clayey soils

This feasibility study examines the use of in situ microbial gas production to engineer the consolidation properties of clayey soils by changing the settlement–time profile. A simple analytical model has been proposed to assess the swelling of the soil during the steady-state gas production, and to predict immediate settlements due to loading at the end of this process. For experimental validation of the suggested technique, Clostridium acetobutylicum, an anaerobic fermentative microorganism, was mixed into clayey-sand samples, fed with a nutrient-rich medium, and allowed to produce gas in situ. A series of standard oedometer tests was performed on gas-containing and gas-free soil specimens. Results showed that, in agreement with the model predictions, in situ gas production caused negligible swelling of the samples, while shifting a significant portion (up to 50%) of total displacement from primary consolidation settlement to immediate settlement without changing total displacements or the coefficient of consolidation.

A critical reappraisal of “preconsolidation pressure” interpretations using the oedometer test

Over the past 70 years, a number of methods have been proposed for the interpretation of the characteristic vertical effective yield stress, or “preconsolidation pressure,” of compressible soils as defined using the standard oedometer test. The concept of the “preconsolidation pressure” has been extraordinarily useful in geotechnical engineering for analysing and predicting settlement behaviour and for normalizing other engineering parameters for comparative purposes. Defining this characteristic stress, however, is often problematic and relies heavily on graphical techniques that are subject to some uncertainty, particularly when using semi-log plots for this purpose. This paper illustrates fundamental difficulties with the interpretation of oedometer test and presents an alternative technique for defining unambiguous values of the vertical effective yield stress.

An anisotropic elastic–viscoplastic model for soft clays

Experimental evidences have shown deficiencies of the existing overstress and creep models for viscous behaviour of natural soft clay. The purpose of this paper is to develop a modelling method for viscous behaviour of soft clays without these deficiencies. A new anisotropic elastic–viscoplastic model is extended from overstress theory of Perzyna. A scaling function based on the experimental results of constant strain-rate oedometer tests is adopted, which allows viscoplastic strain-rate occurring whether the stress state is inside or outside of the yielding surface. The inherent and induced anisotropy is modelled using the formulations of yield surface with kinematic hardening and rotation (S-CLAY1). The parameter determination is straightforward and no additional experimental test is needed, compared to the Modified Cam Clay model. Parameters determined from two types of tests (i.e., the constant strain-rate oedometer test and the 24 h standard oedometer test) are examined. Experimental verifications are carried out using the constant strain-rate and creep tests on St. Herblain clay. All comparisons between predicted and measured results demonstrate that the proposed model can successfully reproduce the anisotropic and viscous behaviours of natural soft clays under different loading conditions.

Time-Dependent Deformation of Dredged Harbor Mud Used as Backfilling Material

Dredged harbor mud is being increasingly used as backfilling and construction material in harbor development or reorganization to gain financial and operative advantages compared to disposal or ex situ treatment of the often contaminated material. However, the suitability of such soft organic sediments as construction material is unclear. This study presents geotechnical parameters for describing the one-dimensional consolidation based on large-scale long-term and standard oedometer tests using organic harbor mud from the Osthafen (East Harbor) reorganization project in Bremerhaven, Germany. Determined compression indices Cc are in the range of peat, whereas the water permeabilities resemble those of clay. The coefficients of consolidation cv vary between 10−9 and 10−8m2∕s and large coefficients of secondary compression Cα between 0.065 and 0.14 are observed. Differences in parameters from large-scale and standard tests can be explained by volume and time effects likely linked to biogeochemical degredation of organic carbon and the resulting methane degassing. A curve fit based on the Levenberg–Marquardt nonlinear least-squares optimization method confirmed the applicability of the Terzaghi theory in combination with a creep term.

Field and Laboratory Tests Investigating Settlements of Foundations on Weathered Keuper Marl

Measured settlements of buildings on the weathered Keuper Marl appeared to be much smaller than calculated settlements, which were based on stiffness modulus from standard oedometer tests. Therefore, both special triaxial K 0-tests and oedometer tests were carried out for an accurate determination of stiffness moduli. Modulus obtained in the triaxial K 0-tests were at least two to three times the values obtained in the oedometer tests. To verify observations from the laboratory tests, the loads and the settlements of two single footings on weathered Keuper mudstone have been measured during construction of a building over 1 year. Also, a large scale footing load test with measurements of deformations were conducted on the weathered Keuper mudstone. The measured settlements of the two single footings and the tested foundation were compared with the settlements based on conventional calculations with moduli from oedometer tests and triaxial K 0-tests. Up to a foundation pressure of σv = 500 kN/m² the calculated settlement based on E S-modulus obtained from triaxial K 0-tests was found to correspond well to the measured deformation. For foundation pressure beyond 500 kN/m², the foundation response was highly non-linear and it could not be described any more with the linear-elastic model. Therefore the footing load test was also simulated by FEM analyses.

Hyperbolic Method for Prediction of Prefabricated Vertical Drains Performance

For predicting the settlement rate of a ground area that incorporates prefabricated vertical drains, the hyperbolic method is herein developed based on Barron’s solution and validated by using three documented case studies. This method is suitable within the degrees of consolidation of 60–90%. Results indicate that the estimated coefficients of radial consolidation ( Cr ) are slightly larger. In two case studies, the estimated Cr values are closer to the coefficients of vertical consolidation obtained from the standard oedometer tests but differ from those values derived from the cone penetration test (CPT) tests. In another case study, where not laboratory results are available, the estimated Cr values fall within a lower bound determined by CPT results. The reason of these differences is due to various factors such as smear and well resistance, the vertical drain type, and its finite drainage capacity. It also appears that, in contrast to the solution obtained by Barron, the settlement versus time curve...

Microstructure, Strength, and Consolidation Properties of Ariake Clay Deposits Obtained from Samplers

Abstract The effect of tube wall friction on the microstructure of Ariake clay samples obtained from a small diameter sampler (45-mm sampler) and their strength and consolidation properties are examined from use of a color laser three-dimensional profile microscope plus unconfined compression, triaxial compression, and standard oedometer tests. The microstructure within 2 mm of the tube wall was disturbed due to wall friction. However, the disturbance in the rest of the sample had other causes and the samples were mechanically homogeneous. The unconfined compressive strength and preconsolidation pressure values obtained from the 45-mm sampler were 20 % to 40 % greater than those of the 75-mm sampler and their sample quality therefore higher.

Geotechnical properties of expansive clay shale in Tabuk, Saudi Arabia

Expansive soils prevail in several parts of Saudi Arabia. Tabuk city, in the northwest, is underlain by a shale formation of Ordovician to Devonian age. Arid climate accelerates the development of expansive clays through desiccation and weathering of the shale. The expansion of the city limits extends to potential areas of swelling and urbanization increases the clay moisture content which leads to soil volume change. This causes significant damage to low-rise buildings and pavements. In this paper, the subsurface conditions and geotechnical properties of the expansive soils in Tabuk are presented. The clay type was identified and its degree of expansion was determined. The swelling parameters were measured utilizing the standard oedometer test and modeled by multiple linear regression. The effect of geological and environmental conditions on the swelling behavior of expansive soils in Tabuk were considered. The modeled swelling values are in good agreement with the measured values.

Horizontal Coefficient of Consolidation of Soft Bangkok Clay

Abstract This paper presents the results of the coefficient of consolidation in the horizontal direction determined from the laboratory and the field through testing, along with back analysis from settlement measurement of embankment constructed with prefabricated vertical drains at the Suvarnabhumi Airport site in Bangkok. Constant rate of strain consolidation tests with radial drainage and standard oedometer tests were conducted to provide the consolidation characteristics of soft Bangkok clay. A 20-mm piezoprobe was used to measure the pore water pressure dissipation characteristics of the soft clay in the field, and the corresponding horizontal coefficients of consolidation were estimated based on established theory. The test results, such as the horizontal coefficients of consolidation and permeability, were compared with back analysis of the constructed runway embankment based on Asaoka method. The results show very good agreement in both horizontal coefficients of consolidation and permeability obtained from different testing methods and back analysis, implying the reliability of the testing methods adopted.

Applicability of 45-mm sampler for Kasaoka clay deposit and the quality of its sample

A new small diameter sampler with two chamber hydraulic pistons (45-mm sampler) was developed, and its applicability is examined through the unconfined compression tests and the standard oedometer tests for samples obtained from both the 45-mm sampler and the 75-mm sampler (75-mmin inner diameter) normally employed in Japan. The samples obtained from the 45-mm and 75-mm samplers have similar strength and consolidationbehaviors for Kasaoka clay deposits.