Volume 56, Nº 3 (2019)

This paper provides a quantitative assessment of the stress-strain state of the "crushed stone pile−surrounding compacted soil−grillage" (cell) system under static and variable loads, taking into account the elastic and elastic-viscous properties of the pile and the surrounding soil. The potential for defining the parameters for deformability and viscosity of the cell, required for carrying out simplified calculations for the foundation known as "piles under the slab," is illustrated. The influence of the pile on the dynamic properties of the base (without piles), including the dynamic response factor, dependent on the frequency of the natural oscillations of the cell, with and without the influence of the pile, is evaluated.

The paper considers the possibility of using the sand compressibility characteristics obtained during laboratory tests instead of those determined based on costly and time-consuming field methods.

Large-size consolidated drained triaxial tests for a gravel and a rockfill were performed. Because of the limit of the apparatus size, test specimens with different maximum grain sizes ranging from 10 to 60 mm, and thus with different particle size distributions, were prepared using the replacement technique (gravel) and mixed method (rockfill) to reduce the particle size of the in-situ soil. The nonlinear or linear shear strength of sandy gravel considering stress state and maximum size was described and verified based on the test data. Furthermore, an approach to estimate the nonlinear shear strength of in-situ sandy soil was developed.

We used finite element analysis to study the impacts of cross-sectional shape, elasticity modulus, hole width, slope angle, and ratio of trench width to tunnel width on the vertical earth pressure on top of cut-and-cover tunnels. The study results show that the effect of the tunnel width coefficient nonlinearly increases with increase in the fill height. The effect of the elasticity modulus coefficient and the coupled effect of slope angle and the ratio of trench width to cut-and-cover tunnel width decreases nonlinearly. We also analyzed two calculation cases for high-filled railway cut-and-cover tunnels and compared the calculated results with those obtained by numerical simulation.

The possibility of predicting the tilt of structures by special static-sounding data processing is examined. A criterion is proposed for the onset of tilting and non-uniform deformations of the foundation. The sequence in processing the results of static sounding in order to determine the direction and magnitude of the tilt of a structure is shown for a practical example.

To study the performance of a sheet-pile wall reinforcing an old gravity revetment, a 3-m-deep excavation was carried out in front of a 10-m-long sheet-pile wall. The excavation was simulated by finite-element modelling and the results were compared with field measurement. The reinforcing sheet-pile wall showed good performance. When the excavation depth was less than 1.2 m the old revetment inhibited the movement at the top of the pile, reducing the lateral displacement. However, for excavations from 2.2 m to 6 m the old revetment had a negative effect on the lateral displacement at the top of the pile, increasing the lateral displacement by 10%-22% compared with that without the revetment. The kick-out stability of the sheet pile was the crucial factor at deep excavation depth. The code used here utilized design and construction standards for quay sheet-pile walls and may be somewhat conservative when used for bank protection.

It is shown that the procedure of rejection of "erroneous" results of testing obtained in the course of evaluation of the computed mechanical and physical characteristics of soils accepted by GOST 20522-201 may lead to "unpredictable" recommendations when the requirement of increasing the maximum result of the tests leads to a decrease in the value of "computed characteristic" down to the minimum result of the tests. Some possible ways of improvement of the procedure of statistical processing of the experimental data with an aim to avoid "nonstandard" conclusions are proposed.

The paper offers a history of collaboration between the Geotechnical societies of the USA (Geo-Institute) and Russia (RSSMGFE), which started in Oakland (USA) in 2012. The author reviews the results of the Russian-American symposium (2018) devoted to the enhancement of the geotechnical regulatory documents in effect in both countries. The paper provides information about studies conducted by the working groups composed of geotechnical experts of both countries.