Journal of Geotechnical and Geoenvironmental Engineering

Tunnel construction in interaction with deep foundations is often a matter of concern in urban areas. However, a great deal of uncertainty is still evident in the differences between regulations for minimum tunnel clearance and in the design of preventive measures for the pile–tunnel interaction effects. To address this problem, this paper presents, analyzes, and compares over 50 reports of case studies, physical models, and full-scale and centrifuge tests on a wide range of layouts and soils. The effects of new tunnels on existing piles are described in terms of mechanisms, induced settlements, and structural forces. The data analysis reveals patterns that could not be found within the limited number of tests of each separate study. Quantitative measurements of pile settlements and axial stresses have been related to the pile position, working load, and tunnel volume loss. The results indicate that most piles do not reach failure and that for piles at a lateral distance of more than two times the tunnel diameter, the settlements are less than 1% of the pile diameter.

In geotechnical engineering analysis and design, the frequency and spacing of borehole information is of great interest, especially when field data are limited. This paper uses random field models to deal with uncertainty in soil properties owing to spatial variability, by analyzing in-situ cone penetration test (CPT) data from a sandy site in northern Denmark. To provide a best estimate of properties between observation points in the random field, a Kriging interpolation approach has been applied. As expected, for small correlation lengths, the estimated field quantities at intermediate locations between data points are close to the mean value of the measured results, and a high uncertainty is associated with the estimate. A longer correlation length reduces the error and implies more variation in the estimated values between the data points.

Numerical techniques commonly used to compute the dynamic response of soil deposits under earthquake shaking are investigated by analyzing data from instrumented borehole arrays. Eleven instrumented vertical arrays are investigated using over 650 recorded ground motions that span a range of shaking intensities. Based on data from the selected borehole arrays, site response predictions using one-dimensional equivalent linear (EQL) analysis, equivalent linear analysis with frequency-dependent soil properties (EQL-FD), and fully nonlinear (NL) analysis are compared with the borehole observations. The results across all sites indicate that at peak shear strains less than about 0.1%, all three site response techniques predict, on average, site amplification within $\pm 20\%$ of observed. At peak shear strains larger than 0.1% and at periods less than about 0.4 s, EQL and NL analyses underpredict site amplification and EQL-FD analyses overpredict site amplification. The underprediction for the EQL and NL techniques may be as large as 70–75% when the shear strength is not considered in the assignment of the shear modulus reduction curve, and the underprediction may still be as large as 55–65% when the shear strength is considered. Over the same period range, EQL-FD analysis overpredicts site amplification by as much as 75% at shear strains larger than 0.1%. These results indicate that one-dimensional site response techniques do not accurately predict site amplification at shorter periods and large strains.

Significant and widespread liquefaction phenomena were observed after the main shock of the Emilia earthquake (Italy) on May 20, 2012. A considerable number of surveys were subsequently performed to accurately test the susceptibility to liquefaction of soil deposits affected by the most severe liquefaction-induced effects and damage. Ground surface morphology was defined in detail by means of LIDAR survey results; subsoil stratigraphy and water table level were inferred from CPT tests and soundings; physical properties and mechanical parameters of soils were obtained from laboratory tests or indirectly inferred from the results of a large number of CPT tests carried out in the area. Two main sandy layers susceptible to liquefaction were identified and appropriately characterized. Seismic loading induced by the main shocks of the sequence was carefully estimated from the peak ground acceleration map produced by the National Institute of Geophysics and Volcanology. More than 90 sites were examined in the area of interest where the most significant cases of liquefaction occurred. A number of statistically independent CPT-based liquefaction field case histories were selected, the critical layer towards liquefaction was identified, and the liquefaction resistance parameter and loading parameter were assessed. Key parameters for each site and critical layer were provided to be added to a select larger and worldwide liquefaction case history database proposed by other authors for estimating CPT-based liquefaction-triggering resistance curves. Finally, applicability to the case study of some more widely used CPT-based simplified approaches was tested. A systematic underestimation of liquefaction potential was found and is discussed, possible reasons are explored, and suggestions are proposed.

The at-rest lateral stress coefficient ($K_0$) is an important soil parameter in geotechnical design problems and yet it is quite elusive in our ability to assess its value, either by laboratory or in situ tests. In this study, an innovative geophysics approach toward the evaluation of the in situ $K_0$ profile with depth is obtained by using small-strain stiffness anisotropy ratio ($G_{0,HH}/G_{0,VH}$) in soils. The newly proposed $K_0$ equation is derived from a database compiled from 12 test sites which have direct $K_0$ measurements, as procured from field tests, either self-boring pressuremeters (SBP) or total stress cells (TSC), and/or laboratory triaxial tests, instrumented consolidometers, and/or suction measurements. The data show a strong relationship between the overconsolidation difference ($\mathrm{OCD}={\sigma }_p^{\prime }-{\sigma }_{vo}^{\prime }$) and stiffness anisotropy ratio, thus enabling a $K_0$ assessment in clays, silts, and sands.

This technical note presents a detailed field study to investigate the installation effects of drilled displacement (DD) piles with a screw-shaped shaft in Shanghai soft clay. Horizontal soil displacements and pore water pressures were measured in the vicinity of two DD piles with a screw-shaped shaft during their installation and subsequent soil consolidation periods. The results show that the horizontal soil displacements induced by the installation of a DD pile with a screw-shaped shaft are mainly concentrated within a circular region with a radius smaller than six times the pile external diameter and that the maximum horizontal soil displacements decrease by 10–20% one day after concreting and then tend to be stable. The excess pore water pressures reach their maximum when the drilling rod reaches the design depth or the concreting is completed and then start to decrease with time following approximately an exponential decay function.