兖州矿区第四系厚松散层沉降特性研究.pdf

Study on Settlement Characteristics of Thick Quaternary Unconsolidated Layer in Yanzhou Mining Area Dissertation ted to Xian University of Science and Technology In partial fulfillment of the requirement For the degree of Doctor of Engineering By Zhang Dingding School of Energy Engineering Dissertation Directed by Professor Chai Jing June, 2015 万方数据 万方数据 论文题目兖州矿区第四系厚松散层沉降特性研究* 专 业矿业工程 博 士 生张丁丁 （签名） 指导教师柴 敬 （签名） 摘 要 地层沉降是一种世界性地质问题，严重时将成为地质灾害。90的地面沉降是由于 大量开采地下资源 （包括地下水、 石油、 天然气和煤炭等） 和进行地下工程不当引起的， 如过度地下水开采引起的地层沉陷、城市地下工程（如地铁）引起的基础沉降、矿山开 采引起的覆岩和地表塌陷等。我国华东矿区开采以立井为主，立井井筒穿过深厚的第四 系松散地层，在煤矿生产过程中立井井筒变形破坏是该地区煤矿安全生产的主要灾害之 一，这种地质灾害严重影响了矿井的安全生产。井壁破裂的跟本原因是厚松散层的失水 压缩沉降，防治厚松散层压缩沉降变形是预防井筒重复破裂的根本。光纤传感技术在松 散层沉降监测中的应用为研究松散层沉降特征，计算和预测松散层沉降变形量提供了可 能。对兖州矿区力学特性、变形机制和沉降特征进行研究，为厚松散层因底部疏排水引 起的厚松散层主压缩层位及岩性的判定提供了理论基础和工程依据，对于华东矿区厚松 散层沉降变形的准确防治、事前预防理井筒破裂具有重要意义。 本文针对兖州矿区第四系厚松散层底部疏排水引起的沉降压缩问题，结合厚松散层 地质构造、水文动态特征及松散层沉降光纤传感监测，对松散层不同岩性土体的流变特 性、沉降机制和松散层沉降特征的相关问题进行了研究，主要开展了以下几个方面的工 作 （1）通过兖州矿区第四系厚松散层砂土、黏土、砂质黏土三种岩性土体高压固结 试验及砂土粒径筛分试验，研究了厚松散层沉降变形机理。对厚松散层砂土、黏土及砂 质黏土蠕变特性进行了研究， 建立了不同岩性松散层应力-应变-时间的非线性流变模型， 试验反应了松散层具有瞬时弹性和黏滞性，单次加载中弹性变形占总变形比例最大的为 砂土、其次为砂质黏土、最小的为黏土，砂质黏土具有明显的弹性后效流变特性；研究 了不同应力历史对蠕变特性的影响，土体施加荷载低于预加荷载时的变形速率小于施加 荷载高于预加荷载时的变形速率；研究了兖州矿区第四系厚松散层砂土层沉降变形机制， 是受颗粒破碎和颗粒滑移的共同作用。 （2）采用自主研制的松散层沉降变形物理模型试验装置，实现了注、失水条件下 厚松散层分布式沉降变形特征的试验研究。研究了厚松散层注水条件下的沉降特征，获 万方数据 得了松散层注水减沉的相关参数；研究了厚松散层底部疏排水条件下的沉降特征；研究 了松散层失、注水下的有效应力增量-应变关系；基于松散层非线性流变本构及应变量 模型建立了松散层沉降的经验预测模型，完善了长期以来厚松散层通过“水位降-沉降 量（应变） ”经验拟合模型对松散层沉降变形特征的部分性表述。模型试验研究表明 注水可以有效改善松散层的应力状态；注水层上部影响高度约为注水水头的 0.024 倍； 注水层下部影响区自底部向注水层位依次发生回弹变形，随注水量增大回弹变形增大； 注水层深度应选择受压缩层位以下位置；松散层失水时应力状态由拉应力状态向压应力 状态转变；垂向压缩随水位持续降由下组含水层向中组黏土隔水层扩展，不同岩性松散 层交界处及注水层位以上区域易产生拉、压应力集中区；松散层注水过程应力-应变曲 线呈非线性，失水过程初期黏土层经历 12 kPa 应力松弛。 （3）理论推导研究了松散层沉降钻孔植入式光纤光栅监测的应变传递，并通过现 场实测进行了松散层应变监测温度补偿。提出了适用于钻孔封装的光纤光栅传感器应变 传递假定条件，建立了考虑钻孔半径、封孔材料弹性模量的钻孔植入式的光纤光栅传感 器松散层应变传递模型；研究了松散层应变传递与钻孔半径、钻孔封装材料的关系。研 究表明封孔材料弹性模量在 815 GPa 的范围内时可以得到较高应变传递率。 （4）以理论及室内试验研究为基础，实测研究了不同水位变化条件下兖州矿区第 四系厚松散层沉降变形特征。分析了松散层应变随时间变化关系；研究了厚松散层水位 动态与对应层位应变变化关系；研究了厚松散层垂向沉降特征，越靠近基岩松散层压应 变越大；提出了厚松散层主压缩层位的判定和预测方法，厚松散层主压缩层位应综合考 虑层厚、变形速率及单位变形量因素，以层位沉降值对总沉降量贡献比例为标准进行判 定。研究结果表明松散层具有明显的回弹延后和压缩滞后现象，中组砂质黏土层长期 处于蠕变变形阶段，少量水位升引起的回弹变形不能抵消长期蠕变变形；下组黏土层和 中组下段砂质黏土层为现阶段主压缩层，研究结果扩展了以往认为华东矿区厚松散层沉 降位于下组或下组底含的认识，应重视中组沉降对井筒变形的影响；厚松散层中组下段 砂质黏土层和下组底含将是松散层沉降的主要贡献层位；应重视发生蠕变松散层对应深 度处井筒的监测和维护。 关 键 词第四系厚松散层；流变特性；沉降模型；沉降特性；压缩层位及岩性 研究类型应用研究 *本文得到国家自然科学基金41027002，高等学校博士学科点专项基金20126121110003的资助 万方数据 Subject Study on Settlement Characteristics of Thick Quaternary Unconsolidated Layer in Yanzhou Mining Area * Specialty Mining Engineering Name Zhang Dingding Signature Instructor Chai Jing Signature Abstract Land subsidence is one of the worldwide geological problems that its evolution will cause serious geological disaster. The large numbers of extraction of underground resources which were water, oil, gas and coal, and the disorder underground engineering created the 90 land subsidence, for instance, the overrated underground water extraction caused strata settlement, civil engineering like subway construction caused foundation base subsidence and mining caused strata movement or surface subsidence. The vertical shaft developing was the main development of the mining area in eastern China, the shaft passed through the thick quaternary unconsolidated layer, and the vertical shaft deation and broken became the major calamity of the mining safety production in these districts, and this type of geological disaster had a strong threat to mining safety production. The root cause of the vertical shaft wall fracture was the water loss compression subsidence of the thick quaternary unconsolidated layer, its subsidence deation prevention was critical to predict the shaft repeat fracture. Application of fiber optic sensing technology in subsidence monitoring of unconsolidated layer made the unconsolidated layer deation behavior research, unconsolidated layer subsidence deation calculation and prediction possible. The fiber optic sensing technology and the research of unconsolidated layer subsidence deation mechanism and behavior provided the theoretical foundation and the engineering basis to the thick quaternary unconsolidated layer subsidence deation monitoring caused by water loss in eastern China mining area, it had important significance to prevent unconsolidated layer subsidence deation and predict the shaft fracture. This dissertation aimed at the compression subsidence caused by water loss at the bottom of the thick quaternary unconsolidated layer in eastern China mining area, combined with the geological structure, the dynamic hydrological characteristics and the unconsolidated layer subsidence monitoring technology based on fiber optic sensing, the rheological characteristics 万方数据 of different lithological soils of unconsolidated layer, the subsidence mechanism and the unconsolidated layer deation behavior have been studied at several aspects which summarized below. 1 The unconsolidated layer deation mechanism was studied by high pressure consolidation test and sand particle size screening test, three kinds of lithology soils of thick quaternary unconsolidated layer in eastern China mining area were tested, which were sand soil, clay soil and sandy clay soil. In this paper, the creep properties of unconsolidated layer in eastern China mining area were studied, and the stress-strain-time nonlinear rheological model of unconsolidated layer at different lithology was built. The tests showed that the unconsolidated layer had instantaneous elasticity and viscosity properties, the sand soil had the larger proportion of elastic deation in a single load, then the sandy clay soil, the clay soil had the smaller elastic deation, and the sandy clay soil had an obvious elastic aftereffect. The effect of different stress history on rheology property was investigated, the deation rate of soil mass at a load bellowed the average stress level was less than it at a load above the average stress level. The subsidence deation mechanism of the unconsolidated layer in eastern China mining area was studied, which showed that the particles breakage and particles slippage have been impacting the subsidence deation together. 2 The physical model test device based on fiber optic sensing technology for unconsolidated layer subsidence deation monitoring was designed and manufactured independently. The model test of thick quaternary unconsolidated layer subsidence deation monitoring based on distributed fiber optic sensing technology was implemented. Deation behaviors of the thick quaternary unconsolidated layer under water injection condition were studied, and the associated parameter to retarding the unconsolidated layer subsidence was obtained too. Then the deation behaviors of the bottom of thick quaternary unconsolidated layer under water loss condition were studied. The relations of the effective stress increment and strain under water loss and water injection of unconsolidated layer were researched. An experienced prediction model of unconsolidated layer subsidence was built based on nonlinear rheology constitutive model and strain model, which completed the expression of unconsolidated layer subsidence deation behaviors in eastern China mining area which was based on the water level lowering-settlement experiential fitting model. Experimental studies showed that water injection effectively improved the stress state of unconsolidated layer; the influent height of the upside of the water injection layer was about 0.024 times as the water head. The water injection depth would be under the 万方数据 compression layer. The stress state changed from tensile stress to compressive stress when the unconsolidated layer loss water, the vertically compress extended from the lower group aquifer to the middle group aquiclude with the water level continually decreasing, and there would generate tensile stress concentration areas at the upper water injection layers and the junctions of unconsolidated layers in different lithology. The stress state of unconsolidated layer water injection process met an elastic-elastoplastic-plastic, 1-2 kPa stress relaxation presented at the initial stage of the water loss process. 3 The strain transfer function of embedded fiber Bragg grating sensors for unconsolidated layer settlement deation detector was theoretically elicited, and the temperature compensation of fiber Bragg grating sensing monitoring was investigated by field test. In this paper, the assumed condition of embedded fiber Bragg grating sensor was presented, and a new mathematical model of strain transferring of the unconsolidated layer and FBG sensors which considered borehole radius and elasticity modulus of the borehole sealing materials, and the relations of strain transfer with borehole radius and borehole sealing material was proposed. It shows that the strain transfer rate would be higher when the elasticity modulus was in the range of 8-15 GPa. 4 A field test was carried out based on er theoretical and experimental studies, and the unconsolidated layer subsidence deation in eastern China mining area was investigated. The relation of unconsolidated layer strain and time was analyzed, the dynamic water level and the corresponding layer strain changes was studied. Characteristics of unconsolidated layer vertical settlements were researched, the compressive strain increased when the unconsolidated layer was near the bed rock. Determination and prediction of main compressive layer in thick quaternary unconsolidated layer was put forwarded, it would comprehensively considered the thickness, deation rate and unit deation value, the determination should on the basis standard of contribution ratio that the layer subsidence to the total subsidence. The results showed that the middle group sandy clay layer was at a long-term creep deation stage, little water level rise could not offset the long-term creep deation. The lower group clay soil layer and the lower segment of middle group sandy clay soil layer were the main compressive layer at the present stage, the research extended the cognition that the thick quaternary unconsolidated layer subsidence in eastern China mining area occurred in the lower group or lower bottom group, and the impacts of middle group subsidence to the shaft fracture should be taken serious. The lower segment sandy clay in middle group and lower bottom layer of the thick unconsolidated would be the main subsidence layer, the shaft depth corresponding to unconsolidated layer which the creep 万方数据 deation occurred should be paid attention to and enhance the deation monitoring and maintaining of these vertical shafts. Key Words Thick Quaternary Unconsolidated Layer; Rheological Characteristics; Subsidence Model; Settlement Characteristics; Compressive Layer Location and Lithology Thesis Applied Research * This paper is financially supported by the National Nature Science Foundation 41027002 and Specialized Research Fund for the Doctoral Program of Higher Education 20126121110003 万方数据 目录 I 目 录 主要符号表 ............................................................................................................................ I 1 绪论 ....................................................................................................................................1 1.1 研究背景 ..................................................................................................................1 1.2 国内外研究现状 ......................................................................................................2 1.2.1 松散层沉降机理研究 ....................................................................................2 1.2.2 松散层沉降变形特征研究.............................................................................7 1.2.3 松散层沉降监测研究 .................................................................................. 11 1.3 兖州矿区厚松散层沉降研究当前存在的问题及研究意义 ................................... 16 1.4 本文主要研究内容及研究方法 ............................................................................. 18 1.4.1 研究内容 ..................................................................................................... 18 1.4.2 研究方法及技术路线 .................................................................................. 18 2 第四系厚松散层土体沉降机理研究 ................................................................................ 20 2.1 试验概况 ................................................................................................................ 20 2.1.1 土样选取 ..................................................................................................... 20 2.1.2 松散层土体单轴高压固结试验 ................................................................... 22 2.1.3 松散层土体基本物理性质试验 ................................................................... 24 2.2 砂土变形特性研究 ................................................................................................. 24 2.2.1 砂土物理性质分析 ...................................................................................... 24 2.2.2 砂土蠕变特性研究 ...................................................................................... 25 2.2.3 砂土非线性流变模型 .................................................................................. 27 2.2.4 应力历史对砂土变形特性的影响 ............................................................... 30 2.3 黏土变形特性研究 ................................................................................................. 31 2.3.1 黏土物理性质分析 ...................................................................................... 31 2.3.2 黏土蠕变特性研究 ...................................................................................... 32 2.3.3 黏土非线性流变模型 .................................................................................. 34 2.3.4 应力历史对黏土变形特性的影响 ............................................................... 37 2.4 砂质黏土变形特性研究 ......................................................................................... 38 2.4.1 砂质黏土物理性质分析 .............................................................................. 38 2.4.2 砂质黏土蠕变特性研究 .............................................................................. 38 2.4.3 砂质黏土非线性流变模型........................................................................... 40 2.4.4 应力历史对砂质黏土变形特性的影响 ....................................................... 43 万方数据 西安科技大学博士学位论文 II 2.5 松散层沉降机制研究 ............................................................................................. 44 2.6 本章小结 ......................................................................................