M Jamiolkowski

Evaluation of Relative Density and Shear Strength of Sands from CPT and DMT

The paper summarises the experience gained by the writers in the interpretation of the cone penetration test (CPT) and flat dilatometer test (DMT) for the assessment of the geotechnical properties of sands. In the first part of the paper, the problem of determining the relative density (D R ) as function of the penetration test results and ambient stress (σ), for silica sands, is dealt with. In the second part of the paper, the assessment of the peak angle of shearing resistance (φ p ) is dealt with. The attention is given to the use of the Boltons strength-dilatancy theory in order to estimate φ p . Engineering correlations, based on Boltons work, are proposed allowing estimation of φ p as function of penetration resistance and σ, taking into account the compressibility and the curvilinear shear strength envelope.

A Review of Instrumentation for Measuring Small Strains During Triaxial Testing of Soil Specimens

Conventional procedures for determining deformations during triaxial tests are based on measurements made externally to the cell. This practice is inadequate, particularly if the small strain stiffness of the soil is being investigated, because errors are introduced which limit the accuracy and resolution of the measurements. The errors can only be eliminated if axial strains are determined internally, within the cell, and locally over the central one third of the specimen. Likewise, the radial dimensions should be monitored at specimen midheight. The last ten years has seen the introduction of a diverse range of small-strain measuring devices. This has been largely in response to recognition of the importance of achieving strain measurement accuracy of at least 10−3% for small-strain stiffness evaluation. This paper summarizes the types of instrumentation currently available and their modes of operation, benefits, capabilities, and limitations. Typical results comparing external and internal strain measurements are presented. A system for classifying internal-strain measuring devices is presented. It is anticipated that test results based on small strain determinations will be a more frequent requirement in the future. Accordingly, the paper is intended to assist prospective users in becoming familiar with the various techniques that have been used and presents information that should enable selection of appropriate equipment for particular applications. Given that improvements in existing systems are warranted, it is hoped that the paper will also provide stimulus for further research and development.

Operational sand stiffness from large scale load tests on reconstituted sand beds

Santrauka Atlikus du didelio masto bandymus ant kvadratinio standaus pamato siekta nustatyti smėlio standumą. Pamato krastinė- 1 m. Betoninio kesono, kuriame 1 m gylyje buvo igilintas ir bandomas atskirasis pamatas, matmenys buvo 4,6×4,6 m (plane), aukstis— 4,05 m. Du Ticino smėlio pavyzdžiai buvo paruosti esant dviem skirtingiems santykiniams tankumams: D R ≅ 45 ir 85%. Mažo tankio smėlio bandymo atveju maksimali apkrova buvo apie 100 kPa. Didelio tankio smėlio atveju ji buvo lygi apie 300 kPa. Sios reiksmės sutampa su sekliųjų pamatų projektuojamomis apkrovų reiksmėmis. Pamatas ant tankaus smėlio pagrindo buvo apkraunamas laipsniskai kas 50 kN jėga, o ant mažo tankio—kas 15 kN jėga. Po kiekvieno žingsnio apkrovimo procesas buvo sustabdomas, kad stabilizuotųsi valksnumo deformacijos. Bandymų metu stebėtos nuosėdžių reiksmės buvo palygintos su reiksmėmis, gautomis atlikus nuosėdžių skaiciavimus pagai analizinį metodą, kuris remiasi statinio zondavimo duomenimis. Sis metodas buvo pasiūlytas 1970 m. Schmert...