影响盾构隧道地表沉降的多因素分析

软土中盾构施工安全一直是工程界关注的重点问题,其研究涉及水-土-结构相互作用以及由于加固引起的土体属性变化等诸多方面。基于渗流-应力耦合理论,在ABAQUS平台上通过二次开发实现盾构开挖过程中土体渗透特性的演化和注浆材料弹性模量及渗透系数的时变性,研究不同埋深、不同地下水位、不同土体特性对盾构隧道地表沉降的影响。研究结果表明:在软土地区,盾构开挖过程中注浆材料弹性模量和渗透系数的时变性对地表沉降影响较大,而土体渗透系数随应变的演化对地表沉降影响不大;隧道埋深、地下水及土体特性均影响开挖对地表的扰动,且土体弹性模量相对影响最大。     

软土地基预制桩沉桩对桩周土体扰动研究

预制桩作为挤土桩或部分挤土桩,在沉桩过程中会挤压周围土体、扰动土体结构。就软土地基预制桩沉桩对周围土体的扰动,采用有限元CEL方法对软土地基预制桩沉桩的全过程进行模拟,得到沉桩过程中和沉桩完成后桩周土体位移规律,并分析了土体弹性模量和泊松比对桩周土体位移的影响。结果表明：沉桩过程中,靠近桩身的土体受桩体拖曳作用,径向位移先增加后减小;沉桩完成后,桩周土体水平位移分布沿径向呈对数形式衰减;随着弹性模量的增加,桩周土体竖向位移逐渐增加;随着泊松比的增加,桩周土体径向位移和竖向位移均增加。     

土体物理参数及空间构形的分形研究

土是由土的颗粒组成，存在着大量的孔隙，研究表明，土体中的颗粒和孔隙表现出分形特征。本文从两个方面介绍了土体物理性质的分形研究：１．分形用于一量描述土体的密度，孔隙表面积等物理参数，２．分形用于定量描述土体的构形，如土体微观结构，孔隙尺寸分布，颗粒尺寸分布等物理性质．     

典型施工作用下的土体性质变异研究

土体受施工扰动的特性主要表现为应力状态和应力路径的改变、工程性质的变异,因此对基坑开挖、桩基施工、强夯及盾构隧道掘进等典型施工作用下,周围土体所产生的扰动影响进行了系统研究.     

超深地连墙施工对软弱地层扰动现场试验研究

为研究软土地层中超深地连墙施工对周边地层扰动影响,对苏州地铁5号线某车站地下连续墙施工进行现场监测研究.针对3幅相邻槽段施工,采用现场监测对施工过程中的土体侧向位移、地表沉降、分层土体沉降、周边建筑物沉降和土压力变化进行观测.发现单幅施工过程中,成槽开挖施工对地层扰动最大,地层变形显著;混凝土浇筑会对土体产生应力补偿,抑制地层变形;在混凝土硬化阶段,土体应力轻微释放,地层变形继续发展并趋于稳定.地层变形规律表明,浅层土体受扰动较大,土体变形较明显,最大土体侧向位移发生在地表,离槽段越近,沉降越明显,深层土体受到扰动则较小.相邻槽段施工对地层变形累积增加,但变化幅度较小.现场地连墙施工引起的周边建筑物沉降和倾斜均在可控范围内.     

管幕预筑法中钢管顶进对地面沉降的影响

为了研究管幕预筑法中密集大直径钢管群顶进对地表沉降的影响,把平行顶管的顶管间距分为3类：大间距、中间距和小间距.明确指出了3类间距范围,总结分析了各种顶管间距情况下已建顶管对新建顶管地表沉降的影响.分析表明,大间距时已建顶管对地层的扰动影响可以忽略,中间距时主要是土体扰动的影响,小间距时既有土体扰动的影响,又有先建顶管管结构的支挡影响.分析Peck公式并对其进行修正,使之可用于预测各种间距下的地面沉降.结合沈阳地铁新乐遗址站施工监测结果,比较了地表沉降监测结果与Peck公式预测值,发现两条曲线吻合情况较好.     

软土结构性对基坑开挖及邻近地铁隧道的影响

为了研究软土地基结构性改变对基坑开挖围护墙变形、地表沉降及其邻近地铁隧道位移和弯矩的影响,针对宁波粉质黏土,采用在重塑土中掺入盐粒和不同质量分数水泥的方式制备人工结构性土,开展一维压缩试验和三轴试验研究原状土与人工结构性土的工程特性,分别通过压缩性指标、抗剪强度指标和结构屈服应力验证和建立水泥质量分数与土体结构性之间的联系;采用Plaxis2D,分析土体结构性改变对基坑开挖过程中围护墙水平位移、地表沉降及其邻近地铁隧道的影响. 研究结果表明,当水泥质量分数为2%时,其压缩性指标、抗剪强度指标和结构屈服应力与原状土基本一致;随着土体结构性降低,扰动度增加,围护墙水平位移、地表沉降和隧道位移急剧增大,其中隧道对于土体扰动度最为敏感,位移增长趋势最为明显,当扰动度为39%时,隧道位移会超过规范允许值;当隧道距离基坑较近时,由于隧道的约束作用,围护墙水平位移和地表沉降较小,但是隧道位移和弯矩会相应增大.     

软土地层盾构掘进土体稳定性模型试验研究

针对软土地层盾构掘进周围土体稳定性问题,自主研制了TJ-TBM2015多功能微型隧道掘进试验平台,通过改变外壳直径以模拟地层损失,采用动力控制系统,微型隧道掘进机可以实现盾构隧道的连续动态机械开挖。基于试验平台进行了地表无超载、地表有局部超载和隧道临近穿越群桩基础3种工况的盾构隧道掘进试验,通过传感器监测不同工况掘进过程中地表沉降变形和隧道周围土体的应力变化,研究土体的稳定性特征,并进行横向对比分析。结果表明,隧道开挖引起的土体应力重分布主要发生在隧道中心1倍直径范围内;局部超载对土体稳定性影响有限,但超载会造成其所在位置附近地表沉降增大;群桩基础对地层起到了一定的加固和隔离作用。     

顶管施工环境影响的二维有限元计算分析

通过建立二维有限元模型，计算了顶管施工中由于开挖支护作用，对土体变形和管道体应力所产生的影响并与现场试验所测得的地表变形进行了对比，通过有限元模拟，探讨了管道在偏斜5、8、10cm时所对应的管道的内力变化情况，并计算了偏斜不同量值时的地表变形情况，同时研究了顶管上层土体加固不同深度和宽度措施对减小地表变形的作用，经研究表明：偏斜对土体变形有很大的影响，通过土体加固措施，可减小地表土体的变形。     

基于土体损失模型软弱地层超大直径钢顶管施工土体变形分析

针对顶管施工引起的土体变形问题,结合深圳市超大直径钢顶管施工项目,基于非等量径向土体损失模型,对Peck公式进行修正,计算得到该地区土体损失率为1.34%,并依托工程实例分析了软弱地层钢顶管施工土体变形规律。分析结果表明：土体损失是引起土体变形的主要因素,顶管顶推力次之,摩阻力对土体变形不敏感;从纵向分析,土体变形具有衰减性,受扰动区域在掌子面前方5 m范围内;从横向分析,土体变形具有扩散性,受扰动区域主要集中在顶管左右两侧6 m及软弱地层内;数值模拟结果与修正Peck曲线、现场实测拟合曲线吻合性良好。通过以上分析认为对软弱地层超大直径钢顶管施工土体易产生变形的区域,应采取一定措施减少其扰动程度。     

Assessment of potential impacts to surface and subsurface water bodies due to longwall mining

Ground movements due to longwall mining operations have the potential to damage the hydrological balance within as well as outside the mine permit area in the form of increased surface ponding and changes to hydrogeological properties. Recently, the Office of Surface Mining, Reclamation and Enforcement(OSMRE) in the USA, has completed a public comment period on a newly proposed rule for the protection of streams and groundwater from adverse impacts of surface and underground mining operations(80 FR 44435). With increased community and regulatory focus on mining operations and their potential to adversely affect streams and groundwater, now there is a greater need for better prediction of the possible effects mining has on both surface and subsurface bodies of water. With mining induced stress and strain within the overburden correlated to changes in the hydrogeological properties of rock and soil, this paper investigates the evaluation of the hydrogeological system within the vicinity of an underground mining operation based on strain values calculated through a surface deformation prediction model. Through accurate modeling of the pre- and post-mining hydrogeological system, industry personnel can better depict mining induced effects on surface and subsurface bodies of water aiding in the optimization of underground extraction sequences while maintaining the integrity of water resources.     

Simulation experiment of AE-based localization damage and deformation characteristic on covering rock in mined-out area

The localization damage and deformation characteristics of multiple rock in mined-out area under thick soil layer were investigated by acoustic emission (AE)-based physical similar simulation experiment and damage test combined with the AE theory on rock damage. During different mining courses, the degree of wall rock suffered from mining disturbed process in mined-out area was different, so did the AE density of initial damage and fracture. Some characteristic parameters, including large events, total events, and energy rate, presented fluctuations with temporal and spatial change and take on a certain extent statistic relation. Subse-quently, the percent of damage degree was defined and divided into 4 stages, and the localization damage and deformation character-istics of surrounding rock in mined-out area and coal pillars were analyzed quantitatively.     

对地下空间进行开发利用的研究

针对当前城市化进程中出现的土地资源不足、环境不断恶化的情况，提出了开发地下空间、发展地下建筑的重要策略；分析了土壤的物理性能、热工条件以及对地下空间的需求量，并用一个具体的地下空间利用的设计方案来论证开发地下空间的必要性和可行性。分析表明，开发地下空间从可持续发展的角度为城市发展指出了一条新途径。     

分级循环荷载下保护层开采扰动煤岩强度及裂隙特性研究

针对回采时反复采动作用下的保护层开采扰动煤岩极易诱发巷道围岩失稳的问题,采用分级循环荷载模拟实际回采工程中采动应力的长期作用,研究保护层开采扰动煤岩在循环荷载作用下的力学强度及变形破坏特性.试验结果表明,在加卸载过程中,受保护层开采扰动煤样的体积膨胀变形明显,煤样内部结构破坏程度比未受保护层开采扰动煤样更高.在加卸载后期,受保护层开采扰动煤样表现为塑性破坏,未受保护层开采扰动煤样发生明显的脆性破坏.相比于未受保护层开采扰动煤样,受保护层开采扰动煤样的峰值强度下降,单位体积（直径为50 mm,高度为100 mm）内的煤样裂隙体积显著增加,峰值强度和裂隙体积占比均沿煤层走向分布较为均匀.处于断层带的未受保护层开采扰动煤样的彼此物性差异较大.受保护层开采扰动煤样比未受保护层开采扰动煤样更符合“煤岩破坏时,裂隙空间复杂程度与峰值强度存在反向对应分布”规律.     

露天煤矿复垦土壤物理特性的空间变异性

土壤空间变异性是影响土壤生产能力的重要因素。本文在大量田间测试的基础上,引入地质统计学分析倒堆法露天采煤复垦土壤物理特性的空间变异性,得出了复垦土壤物理特性空间变异大、压实严重且压实最严重深度为20～40cm的结论;同时也发现土壤空间变异性与采矿方向密切相关;土壤剖面内的空间变异呈明显的规律性;空间变异性与压实成正比等重要结果。这些研究结果为改良土壤和改进采矿与复垦方法提供了依据和方向。     

Longwall mining under gateroads and gobs of abandoned small mine

Due to the use of outdated mining technology or room and pillar mining process in small coal mines, the coal recovery ratio is only 10–25%. In many regions of China, the damage area caused by the small coal mines amounted to nearly one hundred square kilometers. Therefore, special mining techniques must be taken to reclaim the wasted resource in disturbed coal areas. This paper focuses on the different mining methods by analyzing the longwall panel layout and abandoned gateroad(AG) distribution in the abandoned area of Cuijiazhai coal mine in northwestern China. On the basis of three-dimensional geological model, FLAC3 D numerical simulation was employed. The abutment pressure distribution was simulated when the panel face passed through the disturbed areas. The proper angle of the inclined face was analyzed when the panel face passed through the abandoned gateroads. The results show that the head end of the face should be 13–20 m ahead of the tail end. The pillars on both sides of abandoned gateroads had not been damaged at the same time, and no large-area stress concentration occured above the main roof.Therefore, the coal reserves of disturbed areas can be successfully recovered by using underground longwall mining.     

井工开采对边坡稳定性影响的有限元分析

边坡下方井工开采是一个露天煤矿普遍存在的问题。本文采用有限元方法针对某一具体实例进行了数值模拟。模拟考虑了岩体力学特性及岩体结构特征,并模拟了井采过程。通过井采前后边坡岩体应力分析、位移分析,对边坡下方井工开采对边坡稳定性影响获得了一些认识。     

矿产资源开发中矿山地质环境问题响应差异性研究——以陕西潼关、大柳塔及辽宁阜新矿区为例

以陕西潼关、大柳塔及辽宁阜新矿区为例,采用对比分析的方法研究矿产资源开发中矿山地质环境问题差异性响应的主要因素。上述3个矿区矿产资源开发中矿山地质环境问题主要包括:20世纪90年代以前,陕西潼关金矿区是中国矿产资源开发秩序十分混乱的矿区之一,地下开采的采矿废石随意堆排导致了极为严重的矿山泥石流地质灾害及其隐患,“三废”无序排放导致土壤、河水及其底泥的重金属及氰化物污染严重,严重影响人体健康;地处生态环境脆弱带的陕西大柳塔煤矿区,20年大型机械化地下煤炭资源开采导致大面积地面塌陷及其链生的地下水含水层破坏严重,但矿区土地沙漠化程度总体没有呈现加重的趋势,水土环境重金属呈轻度污染;具有百年开发历史的辽宁阜新煤矿区,露天开采使土地生态破坏严重、边坡滑坡灾害频发、土地压占与破坏突出,地下开采引起的地面塌陷对地表建筑物及人居安全影响严重,但相对于金属矿区,该矿区水土环境重金属污染相对轻得多。对比上述3个矿区矿山地质环境问题,得到其差异性响应主要因素:矿产资源种类、原生地质环境条件、开采方式及矿山环境保护意识等。     

煤矸石用于跨基填筑的探讨

通过煤矸石基本物理力学性质的研究,对其在路基填筑中应用的主要问题进行了探讨,认为煤矸石是一种良好的筑路材料。根据这种材料的特点,提出了煤矸石作为筑路材料时压实度的检测方法。实践表明,道路建设中利用煤矸石在技术上是可行的,并具有明显的技术、经济和社会效益。     

Optimization model of unascertained measurement for underground mining method selection and its application

An optimization model of underground mining method selection was established on the basis of the unascertained measurement theory. Considering the geologic conditions, technology, economy and safety production, ten main factors influencing the selection of mining method were taken into account, and the comprehensive evaluation index system of mining method selection was constructed. The unascertained evaluation indices corresponding to the selected factors for the actual situation were solved both qualitatively and quantitatively. New measurement standards were constructed. Then, the unascertained measurement function of each evaluation index was established. The index weights of the factors were calculated by entropy theory, and credible degree recognition criteria were established according to the unascertained measurement theory. The results of mining method evaluation were obtained using the credible degree criteria, thus the best underground mining method was determined. Furthermore, this model was employed for the comprehensive evaluation and selection of the chosen standard mining methods in Xinli Gold Mine in Sanshandao of China. The results show that the relative superiority degrees of mining methods can be calculated using the unascertained measurement optimization model, so the optimal method can be easily determined. Meanwhile, the proposed method can take into account large amount of uncertain information in mining method selection, which can provide an effective way for selecting the optimal underground mining method.