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• Fluid loss is an issue in HDD execution; few experimental studies have addressed it. • When injecting fluid, percolation through pores and pressure rise are competing phenomena. • The study simulated stress conditions and commercial fluid in HDD installation in sand. • Permeability of the sand is the dominating factor, even if fluid loss reducer is used. Horizontal Directional Drilling (HDD) is a trenchless technique for underground infrastructure installation that uses pressurized drilling fluid. Excessive loss of fluid to the formation can cause problems not only for the execution of HDD but also to nearby structures and must, therefore, be avoided. Hydraulic fracture is one of the possible causes and theories to predict the ultimate pressure have been developed, mostly for clays. Luger and Hergarden (1988 , apud Keulen, 2001) developed a hydraulic fracture model particularly for HDD. The present study presents an experimental program carried out on a large flexible calibration chamber in sand using drilling fluid and confining pressures compatible with HDD field conditions. Results show that while local fracturing may occur, causing injection pressure to decrease for a while, permeability is still the dominating factor. [ABSTRACT FROM AUTHOR]

The article responds to the article "Development of Global Correlation Models Between in Situ Stress-Normalized Shear Wave Velocity and Soil Unit Weight for Plastic Soils" by S.-W. Moon and T. Ku in volume 53, issue 10 of the journal. Topics include the measurement of soil plasticity, the estimation of soil weight, and the use of in situ and laboratory tests of soils.

The paper presents the geological–geotechnical characterisation of the very soft organic plastic slightly overconsolidated Sarapuí II clay. Dissipation tests showed no artesian pressure in the deposit. The organic content is in the range 5–18%, the higher values to 3 m depth. NaCl content increases almost linearly with depth, from 7 g/l at 1 m depth to 24–26 g/l at 6 m depth. Kaolinite is predominant throughout the profile, increasing almost linearly with depth. However, smectite has almost the same percentage until 3.5 m depth. The plasticity index varies in the range 60–170% and may be directly related to the clay minerals. G o values decrease with depth, from 14–28 MPa to 1 MPa at 3 m depth, then increase with depth, reaching 5 MPa at the bottom of the very soft material. Vane test results indicated two regions of s u versus depth, the first from 1 m to 5 m depth, with s u in the range 8–12 kPa, the second from 6 m to 8 m depth, with s u in the range 16–18 kPa. There is a trend of linear increase in sensitivity with depth, from 4.5 at 1 m depth to 7–9 at 7 m depth. Salt content does not seem to play a major role in the sensitivity of Sarapuí II clay. [ABSTRACT FROM AUTHOR]

The article presents the author's views regarding a study on the evaluation of remolded shear strength and sensitivity of soft clay through the use of full-flow penetrometers. It mentions that suggestions were presented to obtain the remolded shear strength and the degradation curve from T-bar and ball penetrometers. It emphasizes the data were obtained in T-bar tests performed in Sarapuí II soft clay test site, which is a very soft organic clay deposit with well-known properties.

An overview of in situ tests performed on soft Brazilian soils is presented. Special emphasis is given to the Sarapuf test site and to the test sites in Rio de Janeiro of very high plasticity. Some lessons related to the use of a piezocone with two filters are presented. [ABSTRACT FROM AUTHOR]

The article offers the authors insights on the article "Interaction between Laterally Loaded Pile and Surrounding Soil," by Lusu Ni, Hai Lin, Anne Raich, and Muhannad T. Suleiman. Topics discussed include the use of tactile pressure sheets of measure stresses, soil pressure, and the measurement of horizontal soil stress distribution.