Shear Modulus and Shear Strength of Cohesive Soils

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Abstract: Recent research has clarified the sequence of ground deformation mechanisms that manifest themselves when excavations are made in soft ground. Furthermore, a new framework to describe the deformability of clays in the working stress range has been devised using a large database of previously published soil tests. This paper aims to capitalize on these advances, by analyzing an expanded database of ground movements associated with braced excavations in Shanghai. It is shown that conventional design charts fail to take account either of the characteristics of soil deformability or the relevant deformation mechanisms, and therefore introduce significant scatter. A new method of presentation is found which provides a set of design charts that clarify the influence of soil deformability, wall stiffness, and the geometry of the excavation in relation to the depth of soft ground.

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“…Hara et al (1974) give a correlation for c u with the SPT blow count for a database of cohesive soils from Japan:…”

Section: Parameters For Shanghai Claymentioning

confidence: 99%

Ground movements due to deep excavations in Shanghai: Design charts

Bolton

Lam²,

Vardanega

et al. 2014

Front. Struct. Civ. Eng.

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“…Seed and Idriss (1970) presented results for the variation of Glsu with shear strain for saturated clays, with the corresponding Gmax/su ratios in the range of 2000 to 3000. Similarly, Hara et al (1974) presented a power relationship for the relationship between Gmax and su for cohesive soils, which indicated Gmax was approximately 500 times su. More recently Weiler (1988) presented a linear relationship between G. and su (triaxial compression) based on the plasticity index and overconsolidation ratio (OCR) of the soil, highlighting that no single value of Gmax/su exists for all clays.…”

Section: Laboratorymentioning

confidence: 97%

The Shear Strength and Dynamic Shear Stiffness of Some New Zealand Volcanic Ash Soils

Meyer¹,

Larkin

Pender

2005

SOILS AND FOUNDATIONS

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A significant proportion of the surface deposits of the central and upper half of the North Island of New Zealand consists of volcanic ash soils. Given that New Zealand is situated within an active seismic region, the dynamic properties of these soils are an important geotechnical earthquake engineering consideration. A systematic investigation of three volcanic ash sites was performed to help characterise the dynamic properties of these soils. In situ down-hole and cross-hole seismic tests produced small strain shear modulus (Gmax) values ranging between 17 and 300 MPa, with excellent agreement between the two test methods. Bender element and free vibration torsion testing of specimens trimmed from high quality samples produced Gmax values which were 28% to 75% lower than those measured in the field. This disparity was considered to result from negative pore pressures potentially present in the field and irreversible changes in the structure of the soil that occurred during removal of the soil from its in situ stress environment. Normalised reduction curves (G/Gmax versus shear strain) produced results which were comparable to those presented by other researchers for cohesive soils, though the influence of the plasticity index on the form of the reduction curves was observed to be negligible. Investigation of the Gm.ax,I-surelationship from field investigations of volcanic soils produced average values that ranged between 560 and 890.

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“…This equation was derived from V s measurements in the silty sand and sandy silts typically found in the Mexico City hill and transition zones, obtained with the cross-hole technique and an statistical analysis [18]. For clays, Equation (2) proposed by Hara et al [19] was deemed appropriated to estimated V s profiles, since experimental evidence has proven to provide good results for Mexico City clays (i.e. [18]).…”

Section: Shear Wave Velocity Profilementioning

confidence: 99%

Seismic response evaluation of an urban overpass

Mayoral

Flores

Romo

2010

Earthq Engng Struct Dyn

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The seismic response of one section of a 23 km strategic urban overpass to be built in the so-called transition and hill zones in Mexico City is presented. The subsoil conditions at these zones typically consist on soft to stiff clay and medium to dense sand deposits, randomly interbedded by loose sand lenses, and underlain by rock formations that may outcrop in some areas. Several critical supports of this overpass are going to be instrumented with accelerometers, inclinometers and extensometers, tell tales and end pile cell pressures to assess their seismic performance during future earthquakes and to generate a database to calibrate soil-structure interaction numerical models. This paper presents the seismic performance evaluation of the critical supports located in one section of the overpass. Sets of finite elements models of the soil-foundation-structure systems were developed. Initially, the model was calibrated analyzing the seismic response that an instrumented bridge support exhibited during the June 15th, 1999 Tehuacan (M w = 7) Earthquake. This bridge is located also within the surroundings of Mexico City, but in the lake zone, where highly compressible clays are found. The computed response was compared with the measured response in the free field, pile-box foundation and bridge deck. Once the model prediction capabilities were established, the seismic response of the critical supports of the urban overpass was evaluated for the design earthquake in terms of transfer functions and displacement time histories.

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Shear Modulus and Shear Strength of Cohesive Soils

Cited by 109 publications

References 5 publications

Ground movements due to deep excavations in Shanghai: Design charts

Ground movements due to deep excavations in Shanghai: Design charts

The Shear Strength and Dynamic Shear Stiffness of Some New Zealand Volcanic Ash Soils

Seismic response evaluation of an urban overpass

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