基于光纤感测技术的非均质土体变形室内试验研究

本文在室内建立含黏土夹层的非均质砂土模型,采用光纤感测技术和千分表测量相结合的技术手段测量土体模型在饱水、排水过程中的土体变形规律.研究了承压含水层排水固结和地下水回灌作用下的土体变形,分析变形产生的机理和规律,并评估光纤感测技术测量非均质土体变形的可行性.研究成果对控制土体变形、防治土体地质灾害具有重要意义.     

采场覆岩变形与破坏的分布式光纤监测与分析

提出了采用BOTDR分布式光纤传感技术,对煤层采动过程中覆岩变形与破坏的发育规律进行了监测和分析。以淮南矿区某工作面为例,介绍了监测孔的布置方式和传感光缆的安装方法,提出了采用钻孔安装技术将传感光缆植入到煤层顶板覆岩中,根据工作面回采进度,定期采集传感光缆的应变分布,分析了光缆的应变分布特征及其变化规律,得到了应变分布与地层的对应关系,发现应变分布是不均匀的,传感光缆的应变变化与覆岩模量呈反比,揭示了覆岩变形与破坏的发育规律。根据光缆的应变分布特征、传感光缆光损耗较大的点或者断点所处的层位,结合13-1煤覆岩的岩性组合,得到了垮落带和导水裂缝带的发育高度分别为12.5 m和40.0 m。     

Deformation and failure characteristics of sandstone under uniaxial compression using distributed fiber optic strain sensing

This paper investigates the deformation and fracture propagation of sandstone specimen under uniaxial compression using the distributed fiber optic strain sensing (DFOSS) technology. It shows that the DFOSS-based circumferential strains are in agreement with the data monitored with the traditional strain gage. The DFOSS successfully scans the full-field view of axial and circumferential strains on the specimen surface. The spatiotemporal strain measurement based on DFOSS manifests crack closure and elastoplastic deformation, detects initialization of microcrack nucleation, and identifies strain localization within the specimen. The DFOSS well observes the effects of rock heterogeneity on rock deformation. The advantage of DFOSS-based strain acquisition includes the high spatiotemporal resolution of signals and the ability of full-surface strain scanning. The introduction to the DFOSS technology yields a better understanding of the rock damage process under uniaxial compression.     

Experimental study on uplift mechanism of pipeline buried in sand using high-resolution fiber optic strain sensing nerves

Reliable assessment of uplift capacity of buried pipelines against upheaval buckling requires a valid failure mechanism and a reliable real-time monitoring technique. This paper presents a sensing solution for evaluating uplift capacity of pipelines buried in sand using fiber optic strain sensing (FOSS) nerves. Upward pipe-soil interaction (PSI) was investigated through a series of scaled tests, in which the FOSS and image analysis techniques were used to capture the failure patterns. The published prediction models were evaluated and modified according to observations in the present study as well as a database of 41 pipe loading tests assembled from the literature. Axial strain measurements of FOSS nerves horizontally installed above the pipeline were correlated with the failure behavior of the overlying soil. The test results indicate that the previous analytical models could be further improved regarding their estimations in the failure geometry and mobilization distance at the peak uplift resistance. For typical slip plane failure forms, inclined shear bands star from the pipe shoulder, instead of the springline, and have not yet reached the ground surface at the peak resistance. The vertical inclination of curved shear bands decreases with increasing uplift displacements at the post-peak periods. At large displacements, the upward movement is confined to the deeper ground, and the slip plane failure progressively changes to the flow-around. The feasibility of FOSS in pipe uplift resistance prediction was validated through the comparison with image analyses. In addition, the shear band locations can be identified using fiber optic strain measurements. Finally, the advantages and limits of the FOSS system are discussed in terms of different levels in upward PSI assessment, including failure identification, location, and quantification.     

某顺层岩石滑坡变形机理与治理方案比选研究

山区公路修建过程中常见顺层岩石边坡,尤其是软岩顺层边坡或分布软弱夹层的顺层边坡,处理不当易引发坡体失稳变形。本文就平华公路一处典型的顺层岩石滑坡进行分析论证,根据坡体的地质结构特征与滑坡的变形机理提出三种治理方案,并从技术与经济两方面进行分析比选,最终推荐顺层刷坡与锚固工程结合的综合治理方案,快速有效根治了该处滑坡病害。     

OFDR光纤传感技术在十字岩柱暗挖法物理模型试验中的应用

 现阶段岩土工程模型试验围岩变形监测多采用点式传感器,仅能获得部分测点的应变,而光纤传感作为一种迅速发展的分布式监测技术,能很好地解决这一问题。对于岩土工程室内试验,现有光纤传感技术无法满足试验对空间分辨精度的高要求。对一种新型光纤传感技术光频域反射技术(OFDR)的测量原理和优点进行介绍,并将其应用于浅埋超大断面圆形隧道十字岩柱开挖模型试验中,对整个模型不同断面进行水平向应变连续监测。根据试验结果,结合有限元分析,表明OFDR能准确记录试验过程中模型内部的应变变化,揭示围岩在十字岩柱开挖方法下的变形规律,反映十字岩柱对围岩的支撑作用,为今后隧道工程开挖提供参考。另外通过算法将应变结果转化为位移结果,并与多点位移计的监测结果进行对比分析,偏差在10%以内。结果表明,该技术可应用于岩土工程试验中的变形监测。     

基于数据挖掘的隧道围岩变形响应预测与动态变更许可机制

隧道作为一个完整的系统工程,其已开挖段所揭露岩体的特征信息及其变形数据往往未被有效利用,而这恰恰是对该隧道后续施工有实际指导意义的。为此,基于数据挖掘理念,充分利用已开挖段揭露围岩的先验分布信息,基于高斯过程回归理论(GPR),构建同一设计围岩等级区间段内岩体自然属性与变形间的映射模型,实现对当前掌子面围岩变形收敛值的响应预测。以此作为隧道施工工法变更与否的先导判据,综合超前地质预报解译数据、现场围岩亚级分类结果以及初期勘探资料等多源异构信息,进行围岩稳定性状况的交互式耦合分析,进而构建了隧道变更的动态评估决策与施工许可机制,以实现隧道开挖工法与支护参数的动态调控。此外,利用揭露围岩信息的概率分布统计,耦合GPR与Monte Carlo算法,对隧道设计等级区段内围岩变形的整体失效概率及可靠性评估进行了尝试性探索。     

破碎岩高边坡变形破坏模式及工程治理研究

以金堆城采矿场东帮破碎岩高边坡为研究对象,以实际的野外调查资料为依据,分析了该段边坡的变形破坏机理及变形破坏模式,采用极限平衡法评价了该段边坡的稳定性及其发展趋势,并根据分析结果,提出了综合治理方案。     

Model test study on surrounding rock deformation and failure mechanisms of deep roadways with thick top coal

The deep roadway with thick top coal is a typical roadway difficult to support in deep mining project, and resolving this sophisticated problem to control the stability of surrounding rock is of great significance in safety production of coal mines. In order to explore the surrounding rock deformation and failure mechanisms of such deep roadways, with Zhaolou coal mine in Juye mining area of China as the engineering background, a large-scale geomechanical model test was carried out. The displacement and stress evolution laws of surrounding rock supported by the pressure relief anchor box beam system were researched. Meanwhile, the related results validate and analyze main failure characteristics and mechanisms of the surrounding rock by comparing with field test.     

Considerations of rock dilation on modeling failure and deformation of hard rocks-a case study of the mine-by test tunnel in Canada

For the compressive stress-induced failure of tunnels at depth, rock fracturing process is often closely associated with the generation of surface parallel fractures in the initial stage, and shear failure is likely to occur in the final process during the formation of shear bands, breakouts or V-shaped notches close to the excavation boundaries. However, the perfectly elastoplastic, strain-softening and elasto-brittle-plastic models cannot reasonably describe the brittle failure of hard rock tunnels under high in-situ stress conditions. These approaches often underestimate the depth of failure and overestimate the lateral extent of failure near the excavation. Based on a practical case of the mine-by test tunnel at an underground research laboratory (URL) in Canada, the influence of rock mass dilation on the depth and extent of failure and deformation is investigated using a calibrated cohesion weakening and frictional strengthening (CWFS) model. It can be found that, when modeling brittle failure of rock masses, the calibrated CWFS model with a constant dilation angle can capture the depth and extent of stress-induced brittle failure in hard rocks at a low confinement if the stress path is correctly represented, as demonstrated by the failure shape observed in the tunnel. However, using a constant dilation angle cannot simulate the nonlinear deformation behavior near the excavation boundary accurately because the dependence of rock mass dilation on confinement and plastic shear strain is not considered. It is illustrated from the numerical simulations that the proposed plastic shear strain and confinement-dependent dilation angle model in combination with the calibrated CWFS model implemented in FLAC can reasonably reveal both rock mass failure and displacement distribution in vicinity of the excavation simultaneously. The simulation results are in good agreement with the field observations and displacement measurement data.     

全站仪自由设站隧道围岩变形非接触监测理论和方法的研究

钢尺收敛计隧道围岩变形量测由人工拉尺读数,效率低,与施工相互干扰,测量结果容易受人为因素影响。为满足现代隧道快速、大跨、安全施工需求,提出全站仪围岩变形非接触量测单站、双站自由设站三维坐标法和单站、双站独立坐标测线法的概念和方法,推导围岩变形监测全站仪自由设站坐标转换数学模型。阐述自动全站仪隧道围岩变形非接触监测系统的组成、开发及其特点。以北京东直门地铁隧道施工围岩变形监测为例,说明系统的数据处理、精度评定、图形分析和预报功能,该系统以其高精度、自动化、简便实用的优点在隧道围岩变形监测中起到重要作用。