Página 1 dos resultados de 61 itens digitais encontrados em 0.003 segundos

Influência de parâmetros fundamentais na rigidez, resistência e dilatância de uma areia artificialmente cimentada

Cruz, Rodrigo Caberlon
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
36.7%
Na engenharia em geral existem técnicas consagradas de construção e materiais com comportamentos exaustivamente estudados para um melhor aproveitamento de suas características a favor do engenheiro. Pode-se dizer que uma construção está cada vez mais integrada com o meio ambiente, tanto na economia de materiais quanto no reaproveitamento dos mesmos. O uso mais racional dos materiais também é uma importante alternativa para minimizar custos em uma obra, tais como transporte, escolha do material mais adequado a ser utilizado, tanto por suas características quanto por sua disponibilidade de uso. Já foram realizadas e ainda hoje têm sido realizadas inúmeras pesquisas sobre solos artificialmente cimentados na Universidade Federal do Rio Grande do Sul, visando seu emprego como camada de suporte para fundações superficiais, no encapsulamento de solos contaminados e como barreiras de contenção de contaminação. Analisando as características mecânicas de areia fina artificialmente cimentada, o objetivo desta pesquisa é verificar a validade do uso do fator vazios/cimento na estimativa da resistência à compressão simples, rigidez inicial, resistência à compressão triaxial em condições drenadas com medidas de G0, comportamento tensão-dilatância e comportamento tensão-deformação da areia de Osório. Para tanto foi verificado que o fator vazios/cimento mostrou-se ser um parâmetro muito eficaz e confiável no que diz respeito à previsão de comportamento do material para dosagem de solo-cimento...

Estudo do arrancamento de fundações em solos tratados com cimento; The uplift performance of footings embedded in cement stabilized backfill

Ruver, Cesar Alberto
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
36.48%
Engenheiros geotécnicos, defrontam-se frequentemente com solos de baixa capacidade de suporte. Para viabilizar projetos nestes materiais, pode-se utilizar fundações com grandes dimensões e/ou melhorar a propriedades mecânicas destes solos. Fundações de grandes dimensões podem ser extremamente onerosas e gerar impactos ambientais indesejáveis provocados por grandes movimentações de solo. Em contrapartida, o melhoramento das propriedades mecânicas do solo pode ser obtido por meio de tratamento com agentes cimentantes. Esta técnica tem-se mostrado bastante promissora nas diversas subáreas da geotecnia, como por exemplo, leito e subleito de pavimentação, estabilidade de taludes e terrenos para assentamento de fundações à compressão. A utilização desta técnica em fundações escavadas submetidas à tração ainda é incipiente. Até meados dos anos 1950, os métodos de previsão de desempenho consideravam somente o peso do solo contido em uma superfície ruptura somado ao peso da fundação, como contribuindo na capacidade de carga ao arrancamento. Estudos recentes passaram a incluir uma terceira parcela de resistência devido à resistência ao cisalhamento do solo. A partir de então diversos autores passaram a estudar técnicas de melhoramento e reforços dos reaterros. Num primeiro momento...

Efeito do estado de tensões de cura no comportamento de uma areia artificialmente cimentada; Effect of curing stress state on the behaviour of an artificially cemented sand

Dalla Rosa, Francisco
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
46.65%
O estudo em laboratório do desempenho mecânico de solos artificialmente cimentados está normalmente vinculado à simulação do comportamento de geomateriais naturalmente formados em campo. Por outro lado, o estudo desses novos materiais pode ser também ferramenta útil na previsão do comportamento de aterros de solos artificialmente melhorados. O comportamento de solos cimentados possui considerável influência da densidade e do estado de tensões a que estes materiais estão submetidos durante a fase que compreende a cimentação dessas partículas. Uma alternativa ao estudo da cimentação nestes solos, é a elaboração de um meio em que as amostras possam ser cimentadas sob um estado de tensões específico, e que ao mesmo tempo em que se promove uma redução do índice de vazios do respectivo material. Seguindo nessa analogia, o presente estudo visa apresentar resultados de ensaios triaxiais realizados em amostras de um solo artificialmente cimentado, curadas sob diferentes níveis de tensão e estado de tensões. São abordados os resultados do ponto de vista da rigidez e deformabilidade encontrados para o material. Os resultados demonstraram que a alteração dos estados de tensões de cura, bem como a magnitude das tensões confinantes durante a cura...

Parâmetros de controle da resistência e rigidez de solos granulares artificialmente cimentados

Floss, Márcio Felipe
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
26.4%
A técnica de solo cimento se apresenta como uma ferramenta eficaz no melhoramento de distintos solos, adequando-os às necessidades da engenharia geotécnica. Tal tratamento do solo se aplica, por exemplo, na construção de bases para plataformas rodo-ferroviárias, camada de suporte para fundações superficiais, na prevenção da liquefação de solos granulares em condições fofas, no encapsulamento de solos contaminados e como barreiras de contenção de contaminação. Dessa forma, o presente estudo visa quantificar a influência da quantidade do cimento e da porosidade em relação ao comportamento mecânico das misturas de solos granulares com cimento. Assim, ensaios de resistência à compressão simples, resistência à compressão diametral, ensaios com bender elements e ensaios triaxiais foram realizados com o objetivo de obter uma metodologia de dosagem de solos granulares com adição de cimento. Para tal, foram utilizados um solo artificial areno-pedregulhoso, um solo arenoso grosso de origem granítica, um solo arenoso fino de origem basáltica, um solo arenoso fino de origem granítica e por último, uma areia fina uniforme, estes últimos três materiais com granulometria semelhante, mas com mineralogia e formato de grãos distintos. Em todos os ensaios foram utilizados cimento Portland CP–V (alta resistência inicial)...

The effect of the porosity/cement ratio on the compression behaviour of cemented soil

Sara Rios; António Joaquim Pereira Viana Da Fonseca; Beatrice baudet
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.84%
The compression behavior of an artificially cemented soil was analyzed by the adjusted porosity/cement index using a correlationestablished in the recent literature. It was found that for each value of this index, defined as the ratio of porosity to the volumetric cement content,there was a unique normal compression line (NCL). The NCLs of the cemented specimens for each adjusted porosity/cement index did notconverge with the NCL of the uncemented silty sand at large stresses, but reached a line parallel to it. The NCL of the cemented sand plottedfurther from the NCL of the uncemented sand as the porosity/cement index decreased

Fundamental parameters for the stiffness and strength control of artificially cemented sands

Nilo Cesar Consoli; António Viana da Fonseca; Rodrigo Caberlon Cruz; Karla Salvagni Heineck
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.64%
The treatment of soils with cement is an attractive technique when the project requires improvement of the local soil for the construction of subgrades for rail tracks, as a support layer for shallow foundations and to prevent sand liquefaction. As reported by Consoli et al. in 2007, a unique dosage methodology has been established based on rational criteria where the voids/cement ratio plays a fundamental role in the assessment of the target unconfined compressive strength. The present study broadened the research carried out by Consoli et al. in 2007 through quantifying quantifies the influence of voids/cement ratio on the initial shear modulus (G0) and Mohr-Coulomb effective strength parameters (c#8242;,#981;#8242;) of an artificially cemented sand. A number of unconfined compression and triaxial compression tests with bender elements measurements were carried out. It was shown that the void/cement ratio defined as the ratio between the volume of voids of the compacted mixture and the volume of cement is an appropriate parameter to assess both initial stiffness and effective strength of the sand-cement mixture studied.

Fundamental parameters for the stiffness and strength control of artificially cemented sand

Nilo Cesar Consoli; António Viana da Fonseca; Rodrigo Caberlon Cruz; Karla Salvagni Heineck
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.7%
The treatment of soils with cement is an attractive technique when the project requires improvement of the local soil for the construction of subgrades for rail tracks, as a support layer for shallow foundations and to prevent sand liquefaction. As reported by Consoli et al. in 2007, a unique dosage methodology has been established based on rational criteria where the voids/cement ratio plays afundamental role in the assessment of the target unconfined compressive strength. The present study broadened the research carried out by Consoli et al. in 2007 through quantifying quantifies the influence of voids/cement ratio on the initial shear modulus G and Mohr-Coulomb effective strength parameters c ,fi of an artificially cemented sand. A number of unconfined compression and triaxial compression tests with bender elements measurements were carried out. It was shown that the void/cement ratio defined as the ratio between the volume of voids of the compacted mixture and the volume of cement is an appropriate parameter to assess both initial stiffness and effective strength of the sand-cement mixture studied.DOI: 10.1061/(ASCE)GT.1943-5606.0000008

Parameters controlling stiffness and strength of artificially cemented soils

N. C. Consoli; A. Viana da Fonseca; Rios Silva, S.; R. C. Cruz; A. Fonini
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.36%
The treatment of soils with cement is an attractive technique when a project requires improvement of the local soil for the construction of subgrades for rail tracks, for roads, as a support layer for shallow foundations, and to prevent sand liquefaction. This paper advances understanding of the key parameters for the control of strength and stiffness of cemented soils by testing two soils with different gradings and quantifying the influence of porosity/cement ratio on both initial shear modulus (G0) and unconfined compressive strength (qu). It is shown that the porosity/cement ratio is an appropriate parameter toassess both the initial stiffness and the unconfined compressive strength of the soilcement mixtures studied. Each soil matrix has a unique relationship for G0/qu against adjusted porosity/cement ratio, linking initial stiffness and strength.

Isotropic yielding of unsaturated cemented silty sand

Marcos Arroyo; Miguel Amaral; Enrique Romero; António Joaquim Pereira Viana Da Fonseca
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.36%
Unsaturated cemented soils are frequent both as designed materials and as naturally occurring layers. Both desiccation and cementation act separately as hardening mechanisms, but it is not clear how exactly their effects combine. Do they enhance one another? Are they mutually reinforcing? This study presents results from an experimental campaign aimed at answering these questions. Five different mixtures of soil (a granite saprolite) and cement (with cement contents in the range 0% to 7% on a dry weight basis) are tested in isotropic compression at four different water content levels. Initial void ratio is also controlled, using two initial compaction densities. Loading is performed at constant water content and suction is inferred from a set of water retention curves obtained from parallel psychrometric and pore-size distribution measurements. The range of yield stresses explored in this study covers almost two orders of magnitude and extends up to 7 MPa at suction values of up to14 MPa. Both desiccation and cementation increase yield stress, but their effects are less marked when both act together, and therefore they are not mutually reinforcing.

Fatigue cyclic tests on artificially cemented soil

Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.56%
Artificially cemented soils are frequently used in the infrastructural layers of road or railway platforms but the durability of these structures is often questioned when subjected to cyclic loads. In order to evaluate the fatigue behavior, this paper presents long cyclic triaxial tests over several soil cement mixtures using a very well graded silty sand and Portland cement. In undrained cemented tests, pore pressure decreased as a sign of plastic degradation, resulting that the effective stresses rose during the tests. For that reason, the resilient moduli were normalized to the effective stress, revealing a clear drop on the normalized resilient modulus at a number of cycles depending on the porosity/cement ratio. Notwithstanding, drained and undrained tests presented in this paper performed in uncemented and cemented specimens showed a distinct behavior from granular materials (where the shakedown theory applies) revealing a continuous increase in the accumulated permanent deformations, indicating that long term cyclic triaxial tests, with large number of cycles, may be decisive for a reliable characterization of cyclic triaxial test for bound mixtures.

The Foraging Tunnel System of the Namibian Desert Termite, Baucaliotermes hainesi

Tschinkel, Walter R.
Fonte: University of Wisconsin Library Publicador: University of Wisconsin Library
Tipo: Artigo de Revista Científica
Publicado em 14/06/2010 EN
Relevância na Pesquisa
26.64%
The harvester termite, Baucaliotermes hainesi (Fuller) (Termitidae: Nasutitermitinae), is an endemic in southern Namibia, where it collects and eats dry grass. At the eastern, landward edge of the Namib Desert, the nests of these termites are sometimes visible above ground surface, and extend at least 60 cm below ground. The termites gain access to foraging areas through underground foraging tunnels that emanate from the nest. The looseness of the desert sand, combined with the hardness of the cemented sand tunnels allowed the use of a gasolinepowered blower and soft brushes to expose tunnels lying 5 to 15 cm below the surface. The tunnels form a complex system that radiates at least 10 to 15 m from the nest with crossconnections between major tunnels. At 50 to 75 cm intervals, the tunnels are connected to the surface by vertical risers that can be opened to gain foraging access to the surrounding area. Foraging termites rarely need to travel more than a meter on the ground surface. The tunnels swoop up and down forming high points at riser locations, and they have a complex architecture. In the center runs a smooth, raised walkway along which termites travel, and along the sides lie pockets that act as depots where foragers deposit grass pieces harvested from the surface. Presumably...

Microscale Characterization and Trace Element Distribution in Bacteriogenic Ferromanganese Coatings on Sand Grains from an Intertidal Zone of the East China Sea

Yuan, Linxi; Sun, Liguang; Fortin, Danielle; Wang, Yuhong; Yin, Xuebin
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/03/2015 EN
Relevância na Pesquisa
26.31%
An ancient wood layer dated at about 5600 yr BP by accelerator mass spectrometry (AMS) 14C was discovered in an intertidal zone of the East China Sea. Extensive and horizontally stratified sediments with black color on the top and yellowish-red at the bottom, and some nodule-cemented concretions with brown surface and black inclusions occurred in this intertidal zone. Microscale analysis methods were employed to study the microscale characterization and trace element distribution in the stratified sediments and concretions. Light microscopy, scanning electron microscopy (SEM) and backscattered electron imaging (BSE) revealed the presence of different coatings on the sand grains. The main mineral compositions of the coatings were ferrihydrite and goethite in the yellowish-red parts, and birnessite in the black parts using X-ray powder diffraction (XRD). SEM observations showed that bacteriogenic products and bacterial remnants extensively occurred in the coatings, indicating that bacteria likely played an important role in the formation of ferromanganese coatings. Post-Archean Australian Shale (PAAS)-normalized middle rare earth element (MREE) enrichment patterns of the coatings indicated that they were caused by two sub-sequential processes: (1) preferentially release of Fe-Mn from the beach rocks by fermentation of ancient woods and colloidal flocculation in the mixing water zone and (2) preferential adsorption of MREE by Fe-Mn oxyhydroxides from the seawater. The chemical results indicated that the coatings were enriched with Sc...

Estudo do comportamento mecânico de areias artificialmente cimentadas; Evaluation of the mechanical behaviour of artificially cemented sand

Lopes, Francisco Mateus Gomes
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Civil; MECÂNICA DAS ESTRUTURAS, ESTRUTURAS DE CONCRETO E ALVENARIA E MATERIAIS E PROCESSOS CONSTRUTIVOS Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Civil; MECÂNICA DAS ESTRUTURAS, ESTRUTURAS DE CONCRETO E ALVENARIA E MATERIAIS E PROCESSOS CONSTRUTIVOS
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.6%
Soil improved with the addition of cement have been utilized as an alternative to the construction of various types of geotechnical works, almost always present economic and environmental advantages. This paper presents a study on the usage of cement in the improvement of mechanical properties of sandy soils, characteristic of the region of Natal, collected from its dunes. This research was made in order to analyze the influence of cement content, voids, and also including water immersion and confining pressure. Samples molded from cement-soil mixtures were tested for unconfined compression tests and triaxial tests. The samples had the percentage of cement mixed in 2.5%, 5% and 10% by weight. The cement agent used was the Portland Cement of High Early strength(CPV-ARI), which promoted agility to the experimental procedure for presenting a rapid gain in strenght. The void ratio used ranged from 0.7 (more compact), 0,9 and 1,1(softer). The soil under study can be considered as pure sand. In general, it can be stated that the larger the amount of cement added to the sand studied is, the greater ultimate strength will be. Likewise, as more compact the soil is, the less void ratio and more resistant it will be present. The confining pressure tends to increase the resistance of the specimens. The cementing adopted grades showed that the use of different criteria for failure did not significantly alter the stress-strain parameters for the sand studied. The angle of friction values were found within the typical range of medium and compact sands. Cementing acted in the sand providing an intercepted cohesion which increased enhancing the potential cementation. In triaxial compression tests...

Effect of grain bonding on the stability of a borehole drilled though low cemented formations

Hashemi, S.; Melkoumian, N.; Xu, C.
Fonte: Engineers Australia; CDROM / DVDROM Publicador: Engineers Australia; CDROM / DVDROM
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
26.9%
Achieving an in-depth understanding of the behaviour of low cemented formations such as running sands around a cylindrical borehole is of significant importance in identifying stability problems, designing adequate borehole supports and choosing an efficient drilling method. This paper presents numerical investigations on failure modes of unsupported vertical cylindrical boreholes drilled through weak formations, i.e. low cemented sands where the movement of individual grains is not restricted by sufficient cementation. Distinct element method (DEM) was used for this study. The method enables to simulate sand grains and control normal and shear bonding between them. To simulate actual condition surrounding a borehole at a depth of 80m, a 2m x 2m x 2m cube made up of spherical particles with diameters ranging from 5mm to 70mm was constructed and analysed in the DEM code, PFC3D. The results showed that stress concentration developed in the ground due to the presence of a borehole leads to the formation of a damage zone around that borehole. When there is not sufficient bonding between the sand grains, the interaction between them results in their movement towards the borehole and the eventual collapse of the borehole wall. The effect of fluid flow on stability of boreholes has been studied as well. The cementation between sand grains is mainly caused by the presence of clay particles in the formation. The bonding strength between sand grains is an intrinsic or micro property of the bonding material and is very difficult to measure in laboratory conditions. The results obtained from current research will help to evaluate the effect of particle bonding on the mechanical behaviour of low cemented formations and develop methods to assess borehole stability during and after drilling through such formations.; S. Saeid Hashemi...

The failure behaviour of poorly cemented sands at a borehole wall using laboratory tests

Hashemi, S.S.; Melkoumian, N.; Taheri, A.; Jaksa, M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
Relevância na Pesquisa
36.36%
Abstract not available; S.S. Hashemi, N. Melkoumian, A. Taheri, M. Jaksa

Petrofabric analysis of experimentally deformed calcite-cemented sandstones

Friedman, Melvin
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
26.36%
Cylinders of sand crystals, composed of single crystals of calcite that poikilitically enclose detrital grains, and calcite-cemented sandstones from the Tensleep (Pennsylvanian, Wyoming) and Supai (Permian, Nevada) formations were experimentally deformed dry at confining pressures of 1--5 kilobars and temperatures of 150°--300°C. Thin sections of the undeformed and deformed specimens were studied microscopically to gain a better understanding of the behavior of sandstones in simulated tectonic environments. The calcite and the detrital grains (quartz, feldspar, and others), which have radically different physical and mechanical properties, are shown statistically to have deformed with respect to the principal stresses across the boundaries of the whole specimens rather than with regard to local stress concentrations at grain contacts.

An experimental study on the relationship between localised zones and borehole instability in poorly cemented sands

Hashemi, S.S.; Taheri, A.; Melkoumian, N.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
Relevância na Pesquisa
36.36%
Abstract not available; S.S. Hashemi, A. Taheri, N. Melkoumian; Available online: 20 August 2015

Sedimentary structure of large sand dunes: examples from Dumont and Eureka dunes, California

Vriend, N. M.; Hunt, M. L.; Clayton, R. W.
Fonte: Royal Astronomical Society Publicador: Royal Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf; application/zip
Publicado em /08/2012
Relevância na Pesquisa
26.4%
The current research presents ground penetrating radar images up to 30 m in depth of two large desert dunes in California, USA— a barchanoid ridge in the Dumont field and a linear dune in the Eureka expanse. The radar images show a complicated structure of internal layering with ascending cross-strata, cross-bedding and bounding surfaces cutting through layers. Additional research using seismic refraction surveys and sand sampling refine the image of the subsurface (<5 m) structure. The sedimentary structure of the dune shows a strong internal layering with a cemented structure that may immobilize and influence migration of dune expanses. The subsurface features of the sand dune fields in the Mojave Desert provide evidence of dune building, wind regime and precipitation history.

Dispersibility of glacial loess in particle size analysis, USA.

Mays, M; Nettleton, WD; Greene, Richard; Mason, Joseph A
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.31%
Silt- to sand-size clay aggregates are absent or relatively rare in unweathered glacial loesses, but dominant in parna where they resist dispersion in particle size analysis (PSA). There are reports that some aggregates in glacial loesses also resist dispersion. However, one would expect freeze-dried aggregates to have mostly edge-to-face orientation of the platy clays and to be easily dispersed in PSA. We test this hypothesis in this paper. We selected Midwest and Alaskan soils formed in late-Pleistocene loess derived from glacial outwash and floodplains beyond the late-Pleistocene glacial boundary. Analytical methods are those in use by the National Soil Survey Laboratory. Soil A and B horizons dispersed well as shown by the 1.5 MPa water to clay ratios of <0.6. In the C horizon, silt-size, rounded, compound particles (aggregates) were few to common and randomly distributed. A few were volcanic glass. Other aggregates consisted of carbonates or layer silicates. Layer silicate aggregates dispersed well in PSA, as hypothesised; Fe and carbonate cemented aggregates did not. Most of these dispersed when given an ultrasonic dispersion treatment.

Velocity-porosity relationships: Predictive velocity model for cemented sands composed of multiple mineral phases

Knackstedt, Mark; Arns, Christoph; Pinczewski, Wolf Val
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.36%
Computer simulations are used to calculate the elastic properties of model cemented sandstones composed of two or more mineral phases. Two idealized models are considered - a grain-overlap clay/quartz mix and a pore-lining clay/quartz mix. Unlike experimental data, the numerical data exhibit little noise yet cover a wide range of quartz/cement ratios and porosities. The results of the computations are in good agreement with experimental data for clay-bearing consolidated sandstones. The ef fective modulus of solid mineral mixtures is found to be relatively insensitive to microstructural detail. It is shown that the Hashin-Shtrikman average is a good estimate for the modulus of the solid mineral mixtures. The distribution of the cement phase is found to have little effect on the computed modulus-porosity relationships. Numerical data for dry and saturated states confirm that Gassmann's equations remain valid for porous materials composed of multiple solid constituents. As noted previously, the Krief relationship successfully describes the porosity dependence of the dry shear modulus, and a recent empirical relationship provides a good estimate for the dry-rock Poisson's ratio. From the numerical computations, a new empirical model, which requires only a knowledge of system mineralogy...