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The effective stresses in saturated soils are crucial for geotechnical engineering, particularly in the ocean environment, but no current transducers can directly measure both vertical and lateral effective stresses. Thus, a novel effective stress transducer based on fiber Bragg grating (FBG) technology is developed to directly measure three-dimensional (3D) effective stress in saturated soils. The design of the transducer ensures that pore water pressures inside and outside the transducer are balanced, allowing the strain to solely reflect the effective stress sustained by the soil skeleton. Two FBG sensing elements of the 3D effective stress transducer are designed to measure the vertical and lateral effective stresses by sensing the strain in the thin plate and the sensing cylindrical shell through the porous disk, respectively. Experimental results indicate that the transducer accurately captures the evolution of effective stress under complex static loads and precisely tracks cyclic stress variations under cyclic loadings. Compared to traditional transducers, the lateral earth pressure coefficient derived from the measurement data of the new effective stress transducer shows advanced accuracy and stability. Moreover, the FBG-based transducer effectively monitors effective stress changes during the excavation, capturing soil stress variations and enabling precise excavation stability assessments. The novel 3D FBG-based effective stress transducer offers a vital method for directly measuring the vertical and lateral effective stresses of saturated soils.

期刊论文 2025-07-01 DOI: 10.1016/j.oceaneng.2025.121395 ISSN: 0029-8018

Under the influence of a variety of unfavorable factors, slope instability may occur, so the stability of the slope needs to be analyzed. In this paper, combined with the geological investigation data, the slope engineering geological profiles are derived based on 2D inversion maps of the high-density resistivity (HDR) method to obtain the overburden layer thickness. Then, a finite element model is established based on the mechanical and geometric parameters of the slope to analyze the displacement and deformation characteristics and obtain information about the potential sliding surface. The above analysis results are combined to determine the effective monitoring field and deploy (Fiber Bragg Grating) FBG strain detection piles for deep strain monitoring. The analysis showed that the shape and location of the potential sliding surface of the slope from the numerical simulation are consistent with those delineated by the HDR profile. The monitoring results show the rock and soil on the north side of the slope are soft and have poor stability, which is consistent with the HDR method detection results. Adopting the HDR method to identify the slope's overall geological structure combined with FBG strain detection piles to obtain the deep deformation provided an effective monitoring technique for slope stability assessment.

期刊论文 2024-04-01 DOI: 10.3390/app14083272

Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied. However, it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure. Here, we aim to investigate the subsurface multiphysics of reservoir landslides under two extreme hydrologic conditions (i.e. wet and dry), particularly within sliding masses. Based on ultra-weak fiber Bragg grating (UWFBG) technology, we employ specialpurpose fiber optic sensing cables that can be implanted into boreholes as nerves of the Earth to collect data on soil temperature, water content, pore water pressure, and strain. The Xinpu landslide in the middle reach of the Three Gorges Reservoir Area in China was selected as a case study to establish a paradigm for in situ thermo-hydro-poro-mechanical monitoring. These UWFBG-based sensing cables were vertically buried in a 31 m-deep borehole at the foot of the landslide, with a resolution of 1 m except for the pressure sensor. We reported field measurements covering the period 2021 and 2022 and produced the spatiotemporal pro files throughout the borehole. Results show that wet years are more likely to motivate landslide motions than dry years. The annual thermally active layer of the landslide has a critical depth of roughly 9 m and might move downward in warmer years. The dynamic groundwater table is located at depths of 9-15 m, where the peaked strain undergoes a periodical response of leap and withdrawal to annual hydrometeorological cycles. These interface behaviors may support the interpretation of the contribution of reservoir regulation to slope stability, allowing us to correlate them to local damage events and potential global destabilization. This paper also offers a natural framework for interpreting thermo-hydro-poro-mechanical signatures from creeping reservoir bank slopes, which may form the basis for a landslide monitoring and early warning system. O 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

期刊论文 2024-03-01 DOI: 10.1016/j.jrmge.2023.04.004 ISSN: 1674-7755

The combination of phase change materials (PCMs) with building materials is a flourishing technology owing to the low-temperature change of the materials during phase change and the potential for enhanced heat storage and release. In this study, a new type of PCM energy pile, in which 20 stainless steel tubes (22 mm in diameter and 1400 mm in length) filled with paraffin were bound to heat exchange tubes, was proposed. An experimental system monitored by a fiber Bragg grating (FBG) to study the thermo-mechanical behavior of energy piles and surrounding soil was established. Both the PCM pile and the ordinary pile, with the same dimensions, were tested under the same experimental conditions for comparison. The results indicate that the temperature sensitivity coefficient calibration results of the FBG differ from the typical values by 8%. The temperature variation is more obvious in the ordinary pile and surrounding soil. The maximum thermal stress of the ordinary energy pile is 0.5 similar to 0.6 times larger than that of the PCM pile under flow rates ranging from 0.05 m(3)/h to 0.25 m(3)/h. The magnitudes of the pore water pressure and soil pressure variations were positively correlated with the flow rates.

期刊论文 2024-01-01 DOI: 10.3390/su16010206

Industrial equipment, such as wind turbine foundations and oil and gas pipelines in cold regions, may undergo extrusion/expansion deformation during the freezing and thawing of frozen soil, which affects their power response and safe operation. Measuring the internal deformation of frozen soil can immediately reflect the strain situation of industrial equipment to reduce the risk of equipment operation. We designed a 6-dimensional strain sensor (6-S Sensor) based on fiber Bragg gratings (FBGs) to obtain the spatial principal strain distribution. The strain range, linearity, and average error of the sensor were -4000 to 8000 mu epsilon, 0.997, and 2.94%, respectively. The sensor accurately measured the frozen and thermal expansion of frozen soil at different temperatures in the laboratory. The maximum frozen expansion was 6471.38 mu epsilon, which occurred in the X-direction. The accuracy of spatial principal strain monitoring for the sensor was evaluated through uniaxial compression. The stability of the sensor was verified by the monitoring experiment under natural temperature for half a month. This study provided a pioneering method for monitoring the internal spatial principal strain of frozen soil.

期刊论文 2024-01-01 DOI: 10.1109/TIM.2024.3369138 ISSN: 0018-9456

含冰量是冻土研究的一项重要参数。针对现有含冰量测量的局限性,提出了一种基于光纤布拉格光栅(FBG)的冻土含冰量监测方法。结合冻土温度场,应用内加热FBG刚玉管传感器,通过室内标定试验验证该方法的可行性;基于传统导热系数模型推导出温度特征值与含冰量之间相应函数模型,并应用试验数据进行验证。研究结果表明:试验所得温度特征值随冻土含冰量增加而减小,可以通过该规律初步判断含冰量范围;在温度特性值与含冰量数值关系的拟合中,指数函数模型与本次试验数据拟合度最高,含冰量测量误差小于2%,在可接受范围内;本方法实现冻土含冰量监测具有可行性。

期刊论文 2019-08-12

介绍了现行光纤布拉格光栅(FBG)测试技术的应用领域、传感原理以及常用的封装方式,探索将FBG用于季节冻土路基这种隐蔽工程应变检测中的适应性。主要工作有:(1)基于FBG测试技术的植入梁方法,在传感器布设方面,根据不同测试对象提出了两种封装布设方式:浅置短距离半柔性探测杆和深置长距离半刚性探测杆两种封装布设方式;(2)针对现场测试需要,对电源、光纤传感器、数据采集及分析等整套现场测试系统进行了比较优选;(3)选择两处季节冻土路基作为埋设场地并开展为期1 a的观测。测试结果表明:FBG在-20~30℃的温差范围内保证了很高的存活率,所提出并实现的季节冻土路基应变测试系统具有较高的测试灵敏度和可靠性。该套测试系统为隐蔽工程的物理性质指标测试提供了新的技术手段。

期刊论文 2016-02-23 DOI: 10.16285/j.rsm.2016.02.034
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