Osvaldo de Freitas Neto

Study of Mechanisms That Generate Traffic Noise in the Tire–Pavement Interface for Low-Volume Roads in Brazil

Traffic noise has a negative influence on society, and minimum acoustic comfort standards must be maintained for individuals to be able to perform their daily activities. When traffic speeds exceed 40 km/h, the predominant noise source is tire–pavement interaction. This study assessed noise generated in the tire–pavement interface at different traffic speeds (40, 60, and 80 km/h), for different types of asphalt coatings applied in low-volume roads in the state of Sergipe, Brazil. Coatings included conventional asphalt mix and polymer-modified hot-mix asphalt concrete, cold-mix asphalt, and double bituminous surface treatment. An increase in noise was directly proportional to increased traffic speed and also varied with changing parameters such as voids, surface texture, and roughness. Because of the upper microtexture, a double bituminous surface treatment can be used as a good solution for quiet pavements in low-volume roads.

Influence of Density on the Hydraulic and Mechanical Properties of Sands

This article aims at assessing the influence of relative density on the hydraulic conductivity and shear strength of two sands, denominated S01 and S02, derived from different regions and formation processes. S01 is wind-blown and S2 alluvial. The results of characterization and hydraulic conductivity in constant head tests were presented for both samples. The results of direct shear tests with sand S01 prepared with 5 different void ratios were also presented, for a vertical stress of 100kPa. The S02 sample was prepared with 4 different void ratios and these underwent direct shear testing with vertical stresses of 25kPa and 150kPa. This sample was prepared with the maximum and minimum void ratio and submitted to strength tests at CD triaxial compression with confining stresses of 50kPa, 100kPa and 200kPa. Results showed that even with different grain sizes, and under different density conditions, there were no significant variations in the permeability of the materials. With respect to shear strength, sand S01 obtained higher angle of friction values than sand S02, even though the latter had a higher percent coarse fraction. Sand S02 was relatively similar in terms of friction angle values obtained in direct shear and triaxial compression strength tests.

Comparison of Numerical Methods for Piled Raft Foundations

The methodologies used to calculate piled raft foundations are normally more complex than conventional foundations due to the large number of variables involved in the problem. In the conventional block, the interaction variables considered are only between the pile and the soil. In the piled raft, all the interaction effects must be considered, as follows: plate-soil, plate-piles and piles-soil, simultaneously. The Finite Element Method (FEM) has proven to be a useful tool in analyzing these types of problems. This study aims at assessing the behavior of piled rafts using the Cesar-LCPC numerical tool, version 4.0, which is based on the finite element method. Literature cases of rafts supported by 9, 15 and 16 piles were analyzed. The results obtained were compared with analysis methods presented in the bibliography. The following parameters were assessed: relative spacing (S/D), relative length (L/D), relative stiffness between piles and the soil (KPS), and settlement of piles and the raft. The spacing between piles has a significant influence on load distribution between piles and the raft. Very small spacing provides stiffness to the foundation, which then functions as a conventional pile foundation, in which only the piles absorb the load from the superstructure. The larger the L/D ratio, the lower the settlement and for a given modulus of elasticity of the pile, the increase in relative stiffness (KPS) causes an increase in settlement. In all analyses, the data obtained corroborated the results presented by other methods published in the literature.