The seepage characteristics of coal under the hydraulic-mechanics coupling conditions considering the variation of porosity

At present, jet-grouted horizontal waterproof curtain reinforcement has become an essential method for deep foundation pit groundwater control. However, there is still a lack of an effective theoretical calculation method for horizontal waterproof curtain reinforcement, and there is little research on the seepage laws of foundation pits under different horizontal waterproof curtain conditions. Based on Darcy’s seepage theory, theoretical analysis models of deep foundation pit seepage were established considering the effect of a horizontal curtain in a highly permeable formation. Through the established models, the calculation method of the water inflow and the water pressure under the condition of a horizontal curtain was derived. Then through indoor tests, the reliability of the theoretical calculation method was verified. Furthermore, the established theoretical calculation method is used to analyze the influence of various factors on the water inflow and the water pressure, such as the ratio of hydraulic conductivity of the horizontal curtain to surrounding soil, thickness, and reinforcement position of the horizontal curtain. It is found that the hydraulic conductivity ratio has the most significant influence on the seepage characteristics of the foundation pit. Finally, the design method was applied to an example of the horizontal waterproof curtain of the foundation pit, which is located at Juyuanzhou Station in Fuzhou (China). The water inflow per unit area is 0.36 m3/d in the foundation pit, and this implies that the design method of the horizontal waterproof curtain applied for the excavation case is good and meets the requirements of design and safety.

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Experimental Research on the Effect of Ultrasonic Waves on the Adsorption, Desorption, and Seepage Characteristics of Shale Gas

ACS Omega ◽

10.1021/acsomega.1c02018 ◽

2021 ◽

Author(s):

Xin Li ◽

Jie Zhang ◽

Changjun Wu ◽

Tianyu Hong ◽

Yundong Zheng ◽

...

Keyword(s):

Experimental Research ◽

Shale Gas ◽

Ultrasonic Waves ◽

Seepage Characteristics ◽

Adsorption Desorption

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Pore-scale investigation of hydrate morphology evolution and seepage characteristics in hydrate bearing microfluidic chip

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2021.103881 ◽

2021 ◽

Vol 88 ◽

pp. 103881

Author(s):

Junchen Lv ◽

Kunpeng Xue ◽

Zhaoda Zhang ◽

Zucheng Cheng ◽

Yu Liu ◽

...

Keyword(s):

Microfluidic Chip ◽

Morphology Evolution ◽

Pore Scale ◽

Seepage Characteristics

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CMUT-Based Sensor for Acoustic Emission Application: Experimental and Theoretical Contributions to Sensitivity Optimization

Sensors ◽

10.3390/s21062042 ◽

2021 ◽

Vol 21 (6) ◽

pp. 2042

Author(s):

Redha Boubenia ◽

Patrice Le Moal ◽

Gilles Bourbon ◽

Emmanuel Ramasso ◽

Eric Joseph

Keyword(s):

Signal Processing ◽

Signal To Noise Ratio ◽

Ultrasonic Transducer ◽

Operating Conditions ◽

Geometrical Parameters ◽

Signal To Noise ◽

Coupling Conditions ◽

Sensor Structure ◽

Noise Ratio ◽

Electrical Connections

The paper deals with a capacitive micromachined ultrasonic transducer (CMUT)-based sensor dedicated to the detection of acoustic emissions from damaged structures. This work aims to explore different ways to improve the signal-to-noise ratio and the sensitivity of such sensors focusing on the design and packaging of the sensor, electrical connections, signal processing, coupling conditions, design of the elementary cells and operating conditions. In the first part, the CMUT-R100 sensor prototype is presented and electromechanically characterized. It is mainly composed of a CMUT-chip manufactured using the MUMPS process, including 40 circular 100 µm radius cells and covering a frequency band from 310 kHz to 420 kHz, and work on the packaging, electrical connections and signal processing allowed the signal-to-noise ratio to be increased from 17 dB to 37 dB. In the second part, the sensitivity of the sensor is studied by considering two contributions: the acoustic-mechanical one is dependent on the coupling conditions of the layered sensor structure and the mechanical-electrical one is dependent on the conversion of the mechanical vibration to electrical charges. The acoustic-mechanical sensitivity is experimentally and numerically addressed highlighting the care to be taken in implementation of the silicon chip in the brass housing. Insertion losses of about 50% are experimentally observed on an acoustic test between unpackaged and packaged silicon chip configurations. The mechanical-electrical sensitivity is analytically described leading to a closed-form amplitude of the detected signal under dynamic excitation. Thus, the influence of geometrical parameters, material properties and operating conditions on sensitivity enhancement is clearly established: such as smaller electrostatic air gap, and larger thickness, Young’s modulus and DC bias voltage.

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