Construindo estratégias

Lusíada. Direito. - ISSN 2182-4118. - N. especial (2023). - p. 262

Wavelet Analysis for Evaluating the Length of Precast Spliced Piles Using Low Strain Integrity Testing

The difficulties with the application of low strain integrity testing for evaluating the length of driven precast piles of two sections justify the need for new data acquisition and analysis techniques. The standard time domain analysis of the recorded signals may not allow for distinguishing the desired responses from a pile toe and a splice. In this paper, we propose the use of a set of hammers of different weights and tip materials that will provide various sensitivities of the test to a pile splice. To further analyze the collected data, we study the distributions of phase angles obtained using complex continuous wavelet transform. The characteristic phase shifts that distribute from higher to lower frequencies can be interpreted as responses from a pile toe and a splice. To verify the proposed approaches, a series of numerical simulations were performed using the finite element method for the driven pile models with the different properties of a splice zone. Numerical simulation results show that the pile splices are clearly identified when using the shorter input pulses which can be generated by light hammers with a hard head material. The total length of a simulated pile with a 1 mm air gap between sections was undetectable by standard data analysis approaches and was evaluated when analyzing the wavelet phase angle distributions. Numerically validated data acquisition and analysis techniques were applied to field data analysis and allowed us to confidently identify the length of two-section piles grouped with a pile cap

Wavelet Analysis for Evaluating the Length of Precast Spliced Piles Using Low Strain Integrity Testing

The difficulties with the application of low strain integrity testing for evaluating the length of driven precast piles of two sections justify the need for new data acquisition and analysis techniques. The standard time domain analysis of the recorded signals may not allow for distinguishing the desired responses from a pile toe and a splice. In this paper, we propose the use of a set of hammers of different weights and tip materials that will provide various sensitivities of the test to a pile splice. To further analyze the collected data, we study the distributions of phase angles obtained using complex continuous wavelet transform. The characteristic phase shifts that distribute from higher to lower frequencies can be interpreted as responses from a pile toe and a splice. To verify the proposed approaches, a series of numerical simulations were performed using the finite element method for the driven pile models with the different properties of a splice zone. Numerical simulation results show that the pile splices are clearly identified when using the shorter input pulses which can be generated by light hammers with a hard head material. The total length of a simulated pile with a 1 mm air gap between sections was undetectable by standard data analysis approaches and was evaluated when analyzing the wavelet phase angle distributions. Numerically validated data acquisition and analysis techniques were applied to field data analysis and allowed us to confidently identify the length of two-section piles grouped with a pile cap

Study of influence of "pile-soil" system parameters on the acoustic signal dynamic attributes using numerical modelling

Актуальность исследования обусловлена необходимостью повышения эффективности применения неразрушающих методов контроля качества свайных фундаментов. Основные направления исследований в данной области сосредоточены на изучении возможностей и ограничений существующих методик контроля и разработке новых, позволяющих получить дополнительные сведения о техническом состоянии конструкций. Надежная оценка сплошности и несущей способности свай, выполненная до ввода фундамента в эксплуатацию, минимизирует последующие риски капитальных затрат на устранение аварийных последствий. Распространенные геофизические методики контроля качества фундаментов предназначены для изучения состояния материала конструкций. Описанная в публикации модификация сейсмоакустического метода предлагает использовать дополнительную информацию, извлекаемую из акустических сигналов, для сравнительной оценки контактных условий свай. Это позволяет выполнить требования ГОСТ 5686-2012 "Грунты. Методы полевых испытаний сваями" по выбору характерных мест для проведения статических испытаний, повысить прогностическую эффективность комплекса полевых испытаний в капитальном строительстве. Цель: изучение изменений динамических атрибутов сигналов, зарегистрированных сейсмоакустическим методом, в зависимости от параметров системы "свая-грунт". Объекты: железобетонные сваи и другие фундаменты глубокого заложения. Методы: поверхностный сейсмоакустический метод; атрибутный анализ акустических сигналов; численное моделирование процессов распространения упругих волн. Результаты. Предложена методика сравнительной оценки контактных условий сваи с вмещающим грунтом, основанная на анализе сигналов сейсмоакустического метода с использованием динамических атрибутов нормированной площади спектра и средневзвешенной частоты. Составлено девять серий численных моделей, описывающих характерные системы "свая- грунт". Выполнено трехмерное численное моделирование, для полученных синтетических сигналов рассчитаны атрибуты и построены атрибутные диаграммы. Сделаны выводы о влиянии изменений параметров системы "свая-грунт" на поведение динамических атрибутов отклика.The relevance of the research is caused by the necessity to improve the efficiency of using non-destructive pile testing methods. The directions of research in this area are to determine the capabilities and limitations of standard approaches and to propose the new methods that allow obtaining new information about the structures. The robust estimation of pile integrity and bearing capacity obtained at the stage of quality control of the structures prior to their commissioning minimizes the subsequent risks of capital expenditures for eliminating emergency consequences. Common geophysical quality testing methods are designed to study the material of structures. The modification of the low strain impact method described in the publication suggests using additional information extracted from acoustic signals for a comparative assessment of the contact conditions of piles. This allows meeting the requirements of GOST 5686-2012 "Soils. Methods of field testing by piles" on the conducting static load tests, increasing the predictive efficiency of the complex of field tests in capital construction. The main aim of the research is to study the general patterns in the behavior of the sonic signal dynamic attributes associated with the features of the "pile-soil" system. Objects of the research are reinforced concrete piles and other deep foundations. Methods: low strain impact method; attributes analysis of acoustic signal, numerical modelling of elastic waves propagation. Results. The authors have proposed the technique for comparative assessment of contact conditions, based on the analysis of a low strain impact method signals using the dynamic attributes of the normalized spectrum square and the average-weighted frequency. Nine series of numerical models were compiled describing common "pile-soil" systems. A three-dimensional numerical simulation was performed, attributes were calculated for the obtained synthetic signals and attribute diagrams were constructed. Conclusions are drawn about the influence of changes in the parameters of the "pile-soil" system on the behavior of dynamic response attributes