Abstract in English:

Abstract Point load strength index (PLSI) and slake durability index (SDI) are two important indices of rocks used to evaluate strength and durability for various engineering applications. This research investigates these two indices in sandstones from the Amile formation coupled with petrography, aiming to determine the strength and durability of rock, and test for correlations among mineral constituents, texture, PLSI, and SDI to develop empirical relationships among them. The study provides insights into the geotechnical properties of an important geological formation in the Lesser Himalayan Zone, contributing valuable data for infrastructure development. The methodology involved field sampling, petrographic analysis of thin sections, SDI testing over two cycles, and PLSI testing on irregular lump samples. Correlations between SDI, PLSI, water absorption, packing density, and packing proximity were statistically analyzed. Quarztose sandstones have extremely high durability (SDI: 99.17–99.78%), very strong to extremely strong compressive strength (PLSI: 5.94–14.81 MPa), and low water absorption values (WAV: 0–2.17%). Very high positive correlations were found between SDI and PLSI with R2 =0.804. Based on this correlation, future research can use the equation SDI = 0.0712PLSI + 98.727 to estimate durability from strength for similar sandstones, saving time and resources.

Abstract in English:

Abstract The paper studies the effect of sample reconstitution for three commonly employed procedures, namely static compaction and standard and modified moist tamping methods, in the context of laboratory testing of mine tailing materials. The effect of initial water content and compaction energy on the resulting densities and uniformity of the samples are examined. Equivalencies between different reconstitution methods were established to attain a given target density. Then, the effect of the resulting fabric was investigated by means of isotopically consolidated undrained triaxial tests, on samples prepared with similar densities and water contents but with different reconstitution techniques. The results showed that all reconstitution techniques studied produced samples with acceptable uniformity and good repeatability. Although similar results were obtained across the different methods, the modified moist tamping technique yielded slightly higher undrained peak strengths and exhibited a more pronounced hardening behavior upon reaching the critical state line compared to the static compaction method. In contrast, the moist tamping and static compaction methods produced comparable responses in loose specimens. These results suggest that dynamic and static reconstitution methods may create subtle differences in the fabric of the samples, influencing their behavior under shearing.

Abstract in English:

Abstract Downhole Seismic Testing (DST) is utilized for estimating low-strain shear damping ratio (ηs). Estimates of low strain ηs values are very important for predicting and assessing ground amplification during earthquakes. The low strain ηs estimates also provide for a reference of laboratory tests such as the resonant column test. The Spectral Ratio Technique (SRT) is one of the most utilized analysis techniques for processing seismic data to obtain ηs. The SRT is applied in the frequency domain where the spectral ratio of two data sets and relative arrival times are calculated to obtain the quality factor. The quality factor is inversely proportional to the damping ratio. One of the limitations of the SRT is that it doesn’t account for the raypaths of the source waves. In DST the raypaths are of particular importance due to the fact the source waves will refract as they travel from the surface down to the seismic receiver. This paper outlines a technique, so-called FMDSM-SRT, which facilitates adjusting estimated SRT absorption DST values so that source wave raypaths are accounted for. It is of paramount importance to first implement newly optimal estimation algorithms on extensive test bed simulations prior to processing real data sets. This paper outlines the results from processing a challenging test bed simulation with the FMDSM-SRT algorithm.

Abstract in English:

Abstract The application of loading tests allows us to evaluate the behavior of shallow foundations under real conditions. This article addresses the application of a constitutive model based on Mohr-Coulomb with a cap failure criterion that simulates the compaction of the material and limits its shear strength to describe the behavior of a footing resting on tropical climate soil composed of silt-clay sand. The foundation was tested in terms of axial compression through a static and slowly maintained loading test (SML) until its failure was characterized by significant settlement. A two-dimensional axisymmetric finite element numerical model was used to process the numerical analyses. The numerical model used was able to simulate with high similarity the load-settlement behavior of the footing tested in the loading test, under different water content conditions and preload imposed in the field tests. Additionally, the experimental results facilitated the successful guidance of the numerical analyses, providing parameters to safely analyze similar foundations under other conditions.

Abstract in English:

Abstract The paper presents the finite element modeling of a test embankment built at one of the construction sites of the 2016 Olympic Games in Rio de Janeiro, Brazil. The embankment was raised over 6 weeks to a height of 6.7 m, and was monitored during construction and in the following month. The experiment had to end after a month of measurements due to the need to develop the test area. Instrumentation consisted of electric piezometers, settlement plates and inclinometers. The subsoil featured a pack of sedimentary soils, including soft clays. Firstly, field and laboratory tests were evaluated for numerical modelling parameters, and a sensitivity study of the various parameters was carried out. Program PLAXIS was used with the most suitable soil models for the different soil layers. The time-dependent behaviour of the clayey layers followed Terzaghi’s consolidation theory for pore pressure dissipation coupled with a Buisman (1936)-type solution for viscous behaviour. The final analysis used parameters adjusted by back-analysis of measurements in the monitoring period (2.5 months) in a 3D model. This analysis was extended to 50 years, aiming to predict the long-term behaviour of the embankment. Results of the 50-year analysis indicated that after 20 years the excess pore pressures would have practically dissipated, but that the long-term settlement would be 2.5 times greater than that at the end of construction. Furthermore, the ground horizontal displacement would be about 4 times greater than that measured at the end of construction.