No abstract

Historically, empirical relations are the basis of everyday foundation design. These relations, however, rely on specific datasets, which may not represent the true conditions observed in the field. Even in situ tests rely on empirical correlation formulas, which link observed phenomena to soil properties. These correlations should be updated according to the specific design conditions. Big data (BD) workflows enable the use of massive data available to update the correlations and to provide more accurate predictions of the parameters studied. Thus, in this paper, a BD approach is used to study the relation between the drilling process of continuous flight auger piles and the shear strength properties (SSPs) of the surrounding soils. Soil surveys were carried out to identify the soil strata in the site and to validate the estimates of the SSPs. The results show that indirect measurements are in accordance with typical undrained shear strength and friction angles of the materials considered.

As características da estaca de fundação a ser utilizada em um projeto dependerá de qual tipo escolhido suportará as cargas a serem recebidas da estrutura. No processo de transmissão de cargas a níveis mais profundos e resistentes, observa-se a reação do solo na estaca, seja por atrito lateral ou pela ponta. Os estudos para esses fenômenos podem ser realizados experimentalmente ou por meio da utilização de ferramentas computacionais, trazendo respostas próximas às da realidade. Este trabalho visa estudar o comportamento de elementos de fundação do tipo hélice contínua, buscando compreender a interação soloestaca quanto à influência do coeficiente de atrito lateral no valor da capacidade de carga da estaca. Para isso, estudou-se a execução de uma prova de carga realizada em Brasília e propôs-se a sua simulação por elementos finitos, comparando os resultados dos modelos com os resultados experimentais. Com os resultados de campos de tensões e deformações variou-se os valores dos coeficientes de atrito para compreender o seu comportamento e a melhor opção para retratar o resultado experimental. Constatou-se que existe uma influência direta do coeficiente de atrito nos resultados de capacidade de carga, mostrando que mesmo simulações numéricas simples podem ser de grande ajuda no entendimento do fenômeno de transferência de carga entre solo e estaca.

No abstract

No abstract

Allying technology, theory and engineering practice is one of the main challenges of modern foundation engineering. Current foundation and retaining walls designs may lead to oversizing or undersizing due to the spatial variability of the stratigraphic profile. As the design procedure of piled foundations involves defining the setting depth of the tip, sometimes the piles may not behave as expected, as the soil mass may change significantly even in a small region. In this paper, a study was conducted on the geoenergetic behavior of the soil mass and of the piles of a construction site located in Brasília, DF, Brazil. Previous studies showed that the energy needed to drill a continuous flight auger pile (CFAP) can be related to the strength of the drilled strata. Therefore, a methodological framework was built to further discuss how the geomechanical behavior of CFAPs foundations could be assessed by analyzing the energy needed to drill such piles. Statistical methods, in special the Bootstrap method, were used to assess the possible influences of construction procedures on pile behavior. It was studied how the execution energies of piles vary with initial depth and relative position in the terrain, as well as the influences that they suffer because of the order of execution within a same foundation group and due to the proximity to surrounding retaining walls. The proposed methodology can be used to improve the energy control procedure and performance evaluation of CFAPs, allowing a complementary reliability assessment for the foundation and retaining walls designs and implementations.

Understanding the soil mass and how it behaves is determinant to the quality and reliability of a foundation design. Normally, such behavior is predicted based on laboratory and in situ tests. In the big data era, instead of executing more tests, engineers should understand how to take advantage of ordinary execution procedures to obtain the parameters of interest. Sensors are key components in engineering big data frameworks, as they provide a large number of valuable measured data. In particular, the building process (excavation and concreting) of continuous flight auger piles (CFAPs) can be fully monitored by collecting data from sensors in the drilling machine. This makes this type of pile an ideal candidate to utilize a big data methodology to indirectly obtain some constitutive parameters of the soil being drilled. Thus, in the present paper, the drilling process of CFAPs is modeled by a new physical model which predicts the energy spending during the execution of this type of pile. This new model relies on other fundamental properties of the soils drilled, such as unit weight, cohesion and internal friction angle. In order to show the applicability of the big data methodological framework hereby developed, a case study was conducted. A work site in Brasília-DF, Brazil, was studied and the execution of three CFAPs was monitored. Soil surveys were carried out to identify the soil strata in the site and, therefore, to validate the estimates of Young’s moduli provided by the new formulas. The 95% confidence intervals of Young’s moduli obtained for silty clay, clayey silt and silt were, in MPa, [14.56, 19.11], [12.26, 16.88] and [19.65, 26.11], respectively. These intervals are consistent with literature reports for the following materials: stiff to very stiff clays with low-medium plasticity, medium silts with slight plasticity, and stiff to very stiff silts with low plasticity, respectively. These were the types of materials observed during the site surveys; therefore, the results obtained are consistent with literature reports as well as with field surveys. This new framework may be useful to provide real-time estimates of the drilled soil’s parameters, as well as updating CFAPs designs during their execution. This way, sustainable designs can be achieved, where substrata materials are better characterized, avoiding over-designed structures.

No abstract