Abstract The improper disposal of water treatment plant sludge (WTPS) into the environment can cause irreparable damage. One way to minimize this negative impact is to mix the sludge with the soil, applying the materials in engineering works. In this research, the objective was the use of WTPS for soil stabilization purposes, verifying the improvement of the characteristics and properties of a stabilized clay soil with different sludge percentages for application in waterproofing layers of bottom and final coverage of landfills. Formulations were prepared with additions of 0, 15, 30 and 50% of WTPS. Characterization, compaction, permeability and simple compression resistance tests were carried out. All mixtures met the Brazilian requirements for use in landfill layers, but the mixture composed of 70% soil + 30% WTPS was defined as the best for application in bottom layers and final coverage for the following reasons: it meets the coefficient of permeability and has the highest simple compression resistance of all blends. Furthermore, it is noteworthy that the use of the mixtures, especially 50% soil + 50% WTPS, in daily (intermediate) layers would be an environmentally beneficial alternative that would contribute to the circular economy and to achieving sustainable development goals 11, 12 and 15 by 2030. These applications would bring advantages in the destination of WTPS and reduced consumption of natural resources (soil).

Abstract Non-destructive tests (NDT) are used to verify the length or integrity of elements embedded in soils or rocks. These elements can be piles in foundations or nails and tiebacks in retaining walls. NDTs differ by the types of waves, ways to generate and receive the signal and to analyze data. Tests using sonic wave do not require a pre-installed pipe or wire and they are based on acoustic impedance theory. Despite its dissemination on piles, the application in retaining elements is recent and requires more studies to increase knowledge about these methods. This paper aims to present studies of sonic wave methods in foundation and retaining elements, presenting results, similarities, and differences. Studies from different dates are presented with their relevance, considerations for the different types of elements tested, objectives and methodologies used, to evidence the variables involved within this solution. The sonic test in foundation is widespread and has a greater number of studies. Withing this paper, the variables that interfere in the results of these methods were observed: the velocity of propagation of the sonic wave, the soil stiffness, the location of wave generation and reception and the type of hammer used, evidencing the necessity of further studies, especially in retaining elements. Nondestructive Non destructive NDT (NDT rocks walls waves data preinstalled pre installed theory similarities differences relevance tested solution observed stiffness

Abstract The energy crisis scenario currently going on in Brazil, along with the need to reduce greenhouse emissions, lead to an urgent need to design buildings with greater energy efficiency. Shallow geothermal energy surges as a sustainable alternative to reduce the electricity consumption in buildings related to air conditioning and water heating systems. In Brazil, the use of this technique is still incipient due to the lack of studies that demonstrate its viability in the country's climatic conditions, as well as underground temperature and demand for acclimatization of buildings. The aim of the current work is to present a site characterization for the first geothermal energy investigation carried out in the Brazilian South region. This study is being conducted at the Geotechnical Experimental Site of the State University of Ponta Grossa, and this paper describes the physical, mineralogical, thermal and mechanical characteristics of this site, which comprises a thick layer of a lateritic sandy clay soil over a silty sand layer. The preliminary results of the ground temperatures are consistent with the common trends reported in the literature, showing more expressive oscillations near the ground surface, and becoming approximately constant at higher depths.