Abstract The need to develop and commercialize materials incorporating vegetable fibers has risen over the last 20 years to decrease environmental impact and achieve sustainability. In geotechnical engineering, soil reinforcement with plant-based fibers has gained a lot of interest, especially in temporary earthworks. Soil reinforcement with plant-based fibers is a low-cost, environmentally friendly method with excellent reproducibility and accessibility. In this context, growing appeals for using plant-based fibers such as sisal, coir, curauá, and kenaf for manufacturing new geomaterials have been verified. This paper aims to evaluate the mechanical behavior of soil-fiber composites by insertion of natural coir fibers into a sandy soil matrix with different fiber lengths and contents, where the fibers were randomly distributed in the soil mass. Large-scale direct shear test evaluated the strength-displacement behavior in samples with dimensions of 300 x 300 mm and 200 mm in height. The tests were carried out using fibers with 25 and 50 mm lengths, in 0.50 and 0.75% of fiber contents (in relation to the dry weight of the soil), in a relative density of 50% and 10% moisture content. The overall analysis of the results showed that the coir fibers addition in the well-graded sand increased the shear strength parameters and the ductility, compared with the unreinforced sand.

Abstract Soils are particulate materials, which often stand out for their low shear strength. In most cases, this aspect justifies adapting the geotechnical project for this characteristic, which can be even more problematic in the case of soft sands, since it often occurs in superficial layers in various parts of the metropolitan region of Fortaleza. Therefore, the soil improvement procedure with the addition of small cement fractions can be crucial. The content to be adopted should be such as to bring a more economically viable alternative to the geotechnical design of a shallow foundation, for example. The present research aims to propose a modified Mohr-Coulomb envelope for artificially cemented soils. The proposal is based on the development of two functions that relate shear strength parameters (cohesion and friction angle) with the cement content. In order to assess the proposed functions, triaxial shear tests were performed on the sand with different cement contents. The adjustments presented consistent results. In addition, the proposed envelope was validated using published results encountered in literature.

Resumen El control ejecutivo generalmente se realiza mediante pruebas de carga estática, un método costoso y que requiere mucho tiempo. Se realizaron ensayos de carga estática en ocho pilotes controlados con el objetivo de evaluar la carga última. Este estudio sugiere un enfoque innovador y no destructivo para validar el rendimiento del campo de pilotes de raíces, utilizando un velocímetro digital conectado al cabezal giratorio del equipo de perforación. El método propuesto monitorea las variables relacionadas con la capacidad portante durante la instalación del pilote y propone una ecuación empírica para estimar la capacidad portante última de los pilotes raíz. Para los pilotes evaluados, las predicciones obtenidas con las ecuaciones propuestas coincidieron, así como con los resultados de las pruebas de carga estática, lo que la demuestra como una opción factible y útil para el control ejecutivo de pilotes de raíz, especialmente cuando no se dispone de pruebas de carga.

Abstract Root piles are injected and installed during mortar shaft construction, using pressures of up to 500 kPa. The executive control is typically done through static load testing, an expensive and time-consuming method. Static load tests on eight controlled piles (diameters between 310 mm and 410 mm) were performed, aiming at evaluating pile ultimate load. This study suggests an innovative, non-destructive approach to validate root pile field performance, using a digital speedometer connected to the drilling rig's rotating head. The proposed method monitors variables related to bearing capacity during pile installation and proposes an empirical equation to estimate the ultimate bearing capacity of root piles. For the assessed piles, the predictions obtained with the proposed equations agreed fairly well with results from static load tests, proving it as a feasible and helpful option for the executive control of root piles, especially when load tests are not available.

Abstract A root pile is a form of injection pile (cast-in-place with pressure, with very distinct construction aspects from the known micropile type). During the mortar shaft development, these piles are inserted using distinct injection pressures of up to 500 kPa. Static load tests are typically used to control root piles, which can be an expensive and time-consuming testing procedure. Static load tests were performed on eight monitored piles with diameters of 350 and 410 mm to investigate root pile performance control during pile installation. This research presents a refined and developed alternative methodology for confirming root pile performance using a digital odometer attached to the drill rig's rotatory head. The methodology consists of monitoring variables obtained during pile installation related to pile bearing capacity. Moreover, empirical equations with simple and relevant applications to estimate root pile bearing capacity during installation are proposed. The developed equations produced results consistent with the values obtained from static load testing on the test piles. Therefore, the results suggest that the proposed methodology is a viable alternative for root pile performance control.

Abstract The Expander Body pile (EB) is a combination of a cast-in-situ pile method with an inflated, pump-grouted tip. The EB system's pioneering conjunction with the conventional drilling pile technique has improved work load, foundation security, cost reductions and abrupt displacements in lateritic, porous, unsaturated soils. The aim of this article is to analyze settlement estimates of bored piles equipped with the Expander Body System on tropical lateritic soil, using a deformability modulus obtained from laboratory and field tests. The piles were subjected to compression and uplift load tests. In addition, the estimates of the pile settlement are compared with the measured values, and the findings are discussed. The results strongly support that PMT and SPT tests present the optimal ratios between the measured and estimated settlements for both bored piles and bored piles with the Expander Body System. It can also be observed that CPT tests presented reasonable estimates for tensioned piles. Ultimately, it is verified that straightforward elastic models for the settlement assessment of bored piles can be used reliably in practice for piles equipped with the Expander Body System on tropical unsaturated soils.