Impedance of Inner Saturated Soil to Horizontally Vibrating Large-Diameter Pipe Piles

An analytical solution for the inner soil impedance of saturated soil to a horizontally vibrating large-radius pipe pile was presented. Based on the porous media theory and the assumption that the vertical normal stress is zero, the closed solution of the inner soil impedance of the saturated soil to the movement of the large-diameter pipe pile is obtained. This analytical solution considers the influence of saturated soil parameters on the impedance of the core soil of large-diameter pipe piles. Through numerical examples, the variation law of the inner soil impedance with pile radius, pile length, dimensionless frequency, compression coefficient, effective permeability coefficient, and porosity was analyzed and the pile radius corresponding to effective inner soil impedance is determined.

Optimization of frequency domain impedances for time-domain response analyses of building structures with rigid shallow foundations

The effects of dynamic soil–structure interaction (SSI) have been extensively studied in the last few decades, and proper analysis for the linear elastic case in frequency domain has been established successfully. However, SSI is rarely considered in the design of building structures, and instead, buildings are frequently analyzed using a rigid base assumption and quasi-static loading conditions that ignore SSI and its dynamic nature. Acknowledging these shortcomings, the National Institute of Standards and Technology (NIST) published in 2012 a set of recommendations on time-domain analyses of SSI for building structures compatible with standard finite element packages for consideration in engineering design. The so-called NIST GCR 12-917-21 report introduced a major simplification to enable frequency domain tools to be implemented in time domain analyses. That is, replacing the frequency-dependent soil impedance functions by a single-valued functions read at the flexible-base structure frequency; This work seeks to quantify the accuracy of this simplification considering fully coupled two-dimensional (2D) finite element models (FEM) as the reference. Using a Bayesian approach based on ensemble Kalman inversion (EnKI) and a range of numerical simulations of soil–foundation–building interaction, we estimate the optimal frequency that can be used to estimate soil impedance for time domain analyses; and we evaluate the improvement that the corresponding impedance offers relative to the full FEM results when compared to time domain analyses performed in accordance to the NIST recommendations outlined above.

Measurement of Apparent Electrical Impedance of Soil with Water Flow Inside

Understanding the flow of groundwater is very important, not only for water management but also for the prevention and mitigation of natural disasters. The electrical resistivity method has been established as an effective groundwater exploration method in geological surveys. The purpose of this study is to develop an accurate investigation method for groundwater flow using soil impedance fluctuations. As a preliminary experiment, the apparent soil impedance was measured by applying a low-frequency current through a soil column with water flow inside. The apparent impedance showed fluctuations due to water flow at frequencies above 20 Hz, and the fluctuation range increased with the flow rate of water. It has been proposed that groundwater flow can be detected by measuring impedance fluctuations, and it is considered that this method can be applied to groundwater surveys and embankment and reservoir leak surveys.

CALIBRATION AND ACCURACY OF TWO ELECTROMAGNETIC METHODS OF SOIL MOISTURE MEASUREMENT IN OXISOL

CALIBRATION AND ACCURACY OF TWO ELECTROMAGNETIC METHODS OF SOIL MOISTURE MEASUREMENT IN OXISOL ANDRÉ LUIZ BARROS DE OLIVEIRA SILVA1; REGINA CÉLIA DE MATOS PIRES2; AUGUSTO YUKITAKA PESSINATTI OHASHI3; GLAUCIA CRISTINA PAVÃO4 E GABRIEL CONSTANTINO BLAIN5 1PhD student, Postgraduate in Tropical and Subtropical Agriculture, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. [email protected]. 2 Scientific researcher, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. [email protected]. 3PhD student, Postgraduate in Tropical and Subtropical Agriculture, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. [email protected]. 4PhD student, Postgraduate in Tropical and Subtropical Agriculture, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. [email protected]. 5Scientific researcher, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. [email protected]. 1 ABSTRACT Accurately measuring soil moisture is an important technological challenge. Sensors development and validation for agricultural applications is a relevant research theme. Electromagnetic techniques have been shown to be useful for soil moisture measurement. However, these techniques typically benefit from calibration. In this context, the aim of this study was to calibrate and evaluate the accuracy and precision of the soil moisture measured by two devices with different electromagnetic principles: Frequency Domain Reflectometry (FDR) e High Frequency Soil Impedance (HFSI) in the laboratory with in oxisol. The probes used were Diviner 2000 and Hidrofarm HFM 1010. Soil moisture was measured using both FDR and HFSI probes. A large variation in soil moisture values occurred during the experiment, as it varied from 0.489 m3 m-3 to 0.077 m3 m-3. Both electromagnetic methods showed good correlation compared to the standard method (gravimetric). HFSI probe overestimated the soil moisture values when compared to the gravimetric method, while FDR underestimated the values. Keywords: capacitance probes, HFSI sensor, FDR sensor, high frequency soil impedance. SILVA, A. L. B. O.; PIRES, R. C. M.; OHASHI, A. Y. P.; PAVÃO, G. C.; BLAIN, G. C. CALIBRAÇÃO E PRECISÃO DE DOIS MÉTODOS ELETROMAGNÉTICOS DE MEDIÇÃO DE UMIDADE DO SOLO EM OXISOL 2 RESUMO Medir a umidade do solo com precisão é um importante desafio. O desenvolvimento e validação de sensores para aplicações agrícolas é um tema de pesquisa relevante. As técnicas eletromagnéticas demonstraram ser úteis para a medição da umidade do solo. No entanto, essas técnicas geralmente se beneficiam da calibração. Nesse contexto, o objetivo deste estudo foi calibrar e avaliar a exatidão e precisão da umidade do solo, medida por dois dispositivos com diferentes princípios eletromagnéticos: Reflectometria no Domínio da Frequência (FDR) e Impedância do Solo de Alta Frequência (HFSI) em laboratório em latossolo. As sondas utilizadas foram Diviner 2000 e Hydrofarm HFM 1010. A umidade do solo foi medida usando as sondas FDR e HFSI. Houve uma grande variação nos valores de umidade do solo durante o experimento, de 0,489 m3 m-3 a 0,077 m3 m-3. Ambos os métodos eletromagnéticos mostraram boa correlação em comparação com o método padrão (gravimétrico). A sonda HFSI superestimou os valores de umidade do solo quando comparada ao método gravimétrico, enquanto a FDR subestimou os valores. Palavras-chave: sondas de capacitância, sensor HFSI, sensor FDR, impedância do solo em alta frequência.

Z-Transferred Discrete-Time Infinite Impulse Response Filter as Foundation–Soil Impedance Function for SDOF Dynamic Structural Response Considering Soil–Structure Interaction

This paper proposed a novel dynamic structural analysis of a single-degree-of-freedom system considering soil–structure interaction (SSI). The z-transferred discrete-time infinite impulse response filter serving as a foundation–soil impedance function to get a transfer function between the ground displacement and foundation shear was proposed first. The corresponding time history of the foundation shear caused by a specific input of ground displacement can be determined through the filter obtained, and the succeeding structural responses are then able to be found by the base force propagating function. Case studies comparing the structural dynamic response with and without SSI were carried out. Without consideration of SSI, there was an overestimation of structural displacement for the structure with a shorter period, but in contrast to that, an underestimation for the structure with a longer period was concluded based on the results obtained.