Lucas Festugato

Parameters Controlling Tensile and Compressive Strength of Artificially Cemented Sand

The enhancement of local soils with cement for the construction of stabilized pavement bases, canal lining, and support layer for shallow foundations shows great economical and environmental advantages, avoiding the use of borrow materials from elsewhere, as well as the need of a spoil area. The present research aims to quantify the influence of the amount of cement, the porosity, and the voids/cement ratio in the assessment of unconfined compressive strength qu and splitting tensile strength qt of an artificially cemented sand, as well as in the evaluation of qt /qu relationship. A program of splitting tensile tests and unconfined compression tests considering three distinct voids ratio and seven cement contents, varying from 1 to 12%, was carried out in the present study. The results show that a power function adapts well qt and qu values with increasing cement content and with reducing porosity of the compacted mixture. The voids/cement ratio is demonstrated to be an appropriate parameter to assess both qt and qu of the sand-cement mixture studied. Finally, the qt /qu relationship is unique for the sand-cement studied, being independent of the voids/cement ratio. DOI: 10.1061/ASCEGT.1943-5606.0000278 CE Database subject headings: Tensile strength; Compressive strength; Soil cement; Compacted soils. Author keywords: Tensile strength; Compressive strength; Soil cement; Compacted soils.

Studies on the Dosage of Fiber-Reinforced Cemented Soils

This paper reports on the development of a dosage methodology based of compressive strength for artificially cemented fiber-reinforced soils. The controlling parameters evaluated were the fiber content (F), volumetric cement content (Civ), porosity (η), and cement/porosity ratio (Civ/η). To evaluate the influence of each parameter on the soil response, a number of unconfined compression tests were carried out. The results show that fiber insertion in the cemented soil, for all dry unit weights and for the whole range of cement dosages studied, causes an increase in unconfined compressive strength. The unconfined compressive strength (qu) increased linearly with the amount of cement (Civ) for both the fiber-reinforced and nonreinforced specimens. It was also shown that the cement/porosity ratio, in which volumetric cementitious material content is adjusted by an exponent (0.28 for all the fiber-reinforced and nonreinforced cemented soil mixtures) to give unique correlations for each mixture, is a good para...

Variables Controlling Stiffness and Strength of Lime-Stabilized Soils

Lime treatment is an attractive technique for soil improvement in the construction of rail tracks and pavement layers, in slope protection of earth dams, and as a support layer for shallow foundations. However, there are no dosage methodologies based on rational criteria as in the case of soil-cement technology, where the voids/cement ratio is shown to be a key parameter for the estimation of both strength and stiffness. The present study, therefore, was aimed at quantifying the influence of the amount of lime, porosity, and voids/lime ratio on the initial shear modulus (G0) and unconfined compressive strength (qu) of a lime-treated clayey sandy soil. From the results of unconfined compression tests and bender elements measurements, it was shown, for the soil-lime mixtures investigated, that the voids/lime ratio is an appropriate parameter to assess both initial stiffness and unconfined compressive strength. Also, a unique G0/qu versus voids/lime ratio relationship was established linking the soil-lime mi...

Parameters Controlling Tensile and Compressive Strength of Fiber-Reinforced Cemented Soil

AbstractEnhancement of local soils with fibers and cement for the construction of stabilized pavement bases, canal lining, and support layers for shallow foundations shows great economical and environmental advantages, avoiding the use of borrow materials from elsewhere, in addition to the need of a spoil area. In previous studies, a unique dosage methodology for cemented soils has been established based on rational criteria in which the porosity-to-cement ratio plays a fundamental role in the assessment of the target unconfined compressive strength (qu). The present paper extends previous work by quantifying the influence of the amount of cement, the porosity, and the porosity-to-cement ratio in an assessment on tensile strength (qt) and compressive strength of a fiber-reinforced artificially cemented sand, in addition to the evaluation of the qt/qu relationship. A program of splitting tensile tests and unconfined compression tests considering four distinct dry densities and five cement contents, varying...

Broad-Spectrum Empirical Correlation Determining Tensile and Compressive Strength of Cement-Bonded Clean Granular Soils

AbstractBased on a large database of unconfined compressive strength (qu) and splitting tensile strength (qt) results of cement-bonded clean granular soils with varying characteristics, distinct po...

Theoretical Derivation of Artificially Cemented Granular Soil Strength

AbstractThis paper provides a theoretical derivation for the unconfined compression strength of artificially cemented granular soils. The proposed developments are based on the concept of superposi...

Assessing Failure Envelopes of Soil-Fly Ash-Lime Blends

AbstractThis study aims to establish the influence of curing time and the amount of lime and porosity in the assessment of the Mohr-Coulomb failure envelope of fly ash–lime-treated soils based on unconfined compressive strength (σc) and splitting tensile strength (σt) of such materials. Founded on the concept that the σt/σc relationship is unique for each specific fine-grained soil, fly ash, and lime blends, it is shown that the angle of shearing resistance of a given lime-treated soil is independent of the porosity and the amount of lime of the specimen and that cohesion intercept is a direct function of σc (or σt) of the improved soil, which depends of the porosity and volumetric amount of lime of the soil–fly ash–lime blends. Finally, the concepts are tested with success for a sandy soil treated with fly ash and lime at distinct curing time periods, considering moderate to strong cementation levels.

A sole empirical correlation expressing strength of fine-grained soils – lime mixtures

This paper advances understanding of the key parameters controlling unconfined compressive strength (qu) of lime stabilized fine-grained soils by considering distinct specimen porosities ( ), different lime types and contents and several curing temperatures and time periods. A sole empirical relationship is proposed establishing the normalized unconfined compression strength for lime stabilized fine-grained materials considering all porosities, lime contents, curing temperatures and curing periods studied. From a practical point of view, this means that a very limited number of unconfined compression tests on specific lime stabilized fine-grained material specimens molded with a given lime type and amount, porosity, moisture content and cured for a given time period at a particular temperature, should be sufficient to estimate the strength for an entire range of porosities and lime contents at any given condition. Examples of the practicality of the proposed relationship are presented.

Development of a Cyclic Simple Shear Apparatus

Considering the increasing incidence of cyclic loadings on engineering structures and the enhancement of design analysis, soil testing under cyclic conditions has renewed its importance. Laboratory tests are conducted to simulate as near as possible field conditions. Assumed conditions aid on the choice of the tests to be conducted in order to determinate the relevant geotechnical parameters to each situation observed on the field. The simple shear test is highlighted among the typical tests in Geomechanics. This is the only laboratory test capable of submitting the specimen to plane strain conditions under constant volume while allowing the rotation of principal stresses. Such conditions are representative of situations such as the adjacent shear mechanism to the shaft of piles or under offshore platforms. In this sense a simple shear testing apparatus was developed. Contrasting with commercial equipment where confinement is made by means of a rigid membrane, specimens are confined by cell pressure in the developed apparatus. Consolidation can be conducted under isotropic or anisotropic paths and shearing, under monotonic and cyclic conditions (either stress or strain controlled). Validation tests were conducted on the equipment using an well-known material. The results obtained were satisfactory, validating the developed apparatus.