Visualization and early warning analysis of damage degree of surrounding rock mass in underground powerhouse

Based on the underground powerhouse of Shuangjiangkou hydropower station,Octree theory is adopted to define the indices of the microseismic(MS)spatial aggregation degree and the deviation values of MS count and energy.The relationship between the MS multiple parameters and surrounding rock mass instability is established from three aspects:time,space,and strength.Supplemented by the center frequency of the signal evolution characteristics,A fuzzy comprehensive evaluation model and the evolution trend of the MS event center frequency are constructed to quantitatively describe the early warning state of the surrounding rock mass instability.The results show that the multilevel tree structure and voxels generated based on the Octree theory fit relatively well with the set of MS points in threedimensional space.The fuzzy comprehensive evaluation model based on MS spatial aggregation and MS count and energy deviation values enables three-dimensional visualization of the potential damage area and damage extent of the surrounding rock mass.The warning time and potential damage zone quantified are highly consistent with the characteristics of MS precursors,with wide recognition and field investigation results,which fully validate the rationality and applicability of the proposed method.These findings can provide references for the early warning of surrounding rock mass instability in similar underground engineering.

Key rock mechanical problems of underground powerhouse in Shuibuya hydropower station

The complicated rock structures and the stability of surrounding rocks of the underground powerhouse were the key rock mechanical problems in Shuibuya hydropower station.In order to overcome the related rock mechanical problems encountered during its construction,a comprehensive research was carried out for the underground powerhouse in Shuibuya hydropower station based on a detailed geological survey.It covers the investigations on the initial in-situ stress distribution features,rock mechanical properties,engineering rock mass classifications by different methods,numerical modeling for stability and support analysis,proper measures for rock excavation and support.The results show that the rock excavations of the underground powerhouse under the given geological conditions can be controlled effectively.Some measures,suggested by the designers,are proved to be rational and effective.These measures mainly consist of:(1) the soft rock replacements by concrete in local area below the crane beam,(2) the shotcrete and reinforcement by rock bolts and anchor cables in surrounding rocks,and (3) 2 m concrete placement on the rock bench between adjacent tailrace tubes.The engineering practice shows that the treated surrounding rocks have a good overall stability.The deformation behaviors observed by safety equipments are within the designing limits.The research conclusions on the related rock mechanical problems,prior to the underground powerhouse excavations,are reliable.

Stability analysis of surrounding rock mass in underground powerhouse considering damage effect of microfractures

A high-precision microseismic(MS)monitoring system was built to monitor surrounding rock microfractures in the underground powerhouse on the left bank of Shuangjiangkou Hydropower Station.The surrounding rock damage area with spatiotemporal clustering of MS activities was studied for qualitative analysis of the damage mechanism of surrounding rock microfractures,based on the source parameters of MS events.The surrounding rock microfracture scale characterized by the source radius of MS events was considered to establish the constitutive relation.MS information was imported into the model for numerical analysis using fast Lagrangian analysis of continuain 3 dimensions(FLAC^(3D)).The results indicated that the numerical simulation results considering MS damage can better reflect the actual situation of the field.The surrounding rock microfractures mainly showed mixed failure characteristics.Shear failures appeared in localized areas while the fracture scale of sections from K0e33 m to K0e15 m on the vault was large.The deformation increment caused by microfracture damage in the shallow surrounding rock of the top arch accounted for 10%e13%,and the stress decrement in the surrounding rock caused by microfracture damage accounted for about 10%.

Engineering rock mechanics practices in the underground powerhouse at JinpingⅠhydropower station

Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station, a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted. The distribution of strata, lithology, and initial geo-stress, the excavation process and corresponding rock mass support measures, the deformation and failure characteristics of the surrounding rock mass, the stress characteristics of anchorage structures in the cavern complex, and numerical simulations of surrounding rock mass stability and anchor support performance are presented. The results indicate that the underground powerhouse of Jinping I hydropower station is characterized by high to extremely high geo-stresses during rock excavation. Excessive surrounding rock mass deformation and high stress of anchorage structures, surrounding rock mass unloading damage, and local cracking failure of surrounding rock masses, etc., are mainly caused by rock mass excavation. Deformations of surrounding rock masses and stresses in anchorage structures here are larger than those found elsewhere： 20% of extensometers in the main powerhouse record more than 50 mm with the maximum at around 250 mm observed in the downstream sidewall of the transformer hall. There are about 25% of the anchor bolts having recorded stresses of more than 200 MPa. Jinping I hydropower plant is the first to have an underground powerhouse construction conducted in host rocks under extremely high geo-stress conditions, with the ratio of rock mass strength to geo-stress of less than 2.0. The results can provide a reference to underground powerhouse construction in similar geological conditions.

Comparative analysis of deformation and failure mechanisms of underground powerhouses on the left and right banks of Baihetan hydropower station

The stability of the surrounding rocks of large underground powerhouses is always emphasized during the construction process,especially in large-scale underground projects under construction,such as the Baihetan hydropower station in China.According to field investigations,numerical simulations and monitoring data analysis,we present a comparative analysis of the deformation and failure characteristics of the surrounding rocks of underground powerhouses on the left and right banks of the Baihetan hydropower station.The failure characteristics and deformation magnitude of the underground powerhouses on the left and right banks are quite different.Under the disadvantageous condition where the maximum principal stress intersects the axis of the powerhouse at a large angle,the left bank underground powerhouse shows prominent stress-controlled failure characteristics such as spalling,slack collapse and concrete cracking.Although the maximum principal stress is in the favorable condition which intersects the right bank powerhouse at a small angle,the relatively high intermediate principal stress with an angle subvertical to the right bank powerhouse plays an essential role in its deformation and failure,indicating that the influence of high intermediate principal stress cannot be ignored.In addition,structural plane-controlled failure and large deformation are also more evident on the right bank due to the extensive distribution of weak structural planes and complex surrounding rock properties.

Dust Diffusion Simulation in the Third Layer Construction of Underground Powerhouse

Under forced ventilation,the dust diffusion of underground powerhouse construction is investigated using a 3D high Reynolds number k-ε model.The interfacial momentum transfers and the wall roughness in the wall function are considered.Ventilation in the third layer of underground powerhouse of Xiangjiaba hydropower station is used as a case.The geometric structure has a decisive effect on the airflow distribution.It is concluded that the dust concentration decreases gradually with the increase of the ventilation time.However,iso-concentration curves have the same tendency after 1 800 s.The dust concentration meets the ventilation and dust-prevention health standard after 2 300 s.The prediction by the present model is confirmed by the experimental measurement by Nakayama.

某工程浅埋大跨度地下厂房围岩块体稳定性分析

通过块体理论对某水电站工程浅埋大跨度地下厂房围岩进行块体稳定性分析,结果表明不稳定块体主要分布于顶拱部位,地下水对块体稳定影响较大;随着地震动参数的增加,块体安全系数会随之降低,但降幅不大;地应力对顶拱块体稳定性影响较大;喷混凝土与锚杆相结合的支护措施对不稳定块体加固效果较好。

大型抽水蓄能电站地下厂房结构自振特性分析

自振特性分析是抽水蓄能电站地下厂房结构振动研究的基础。以丰宁抽水蓄能电站地下厂房为计算实例,建立了变速机组段地下厂房结构的三维有限元模型。首先采用模态分析方法研究了不同边界条件对地下厂房整体结构及楼板、立柱、楼梯、风罩和机墩等局部结构自振特性的影响,然后分析了丰宁地下厂房可能存在的振源,并对厂房整体及局部结构进行了共振复核。结果表明,上下游边墙弹簧约束条件的增强可以有效提高厂房整体结构自振频率,但对楼板局部自振频率的大小影响不大,对楼梯自振频率也无影响。固定边界使厂房整体结构各阶自振频率显著增大,对楼板、立柱、风罩和机墩等局部结构自振频率影响也较大。在可能的振源作用下,厂房整体结构和各局部结构发生共振的可能性很小。

四川省大渡河金川水电站地下厂房岩壁吊车梁岩台超挖处理措施及锚杆注浆时机研究

为了解决金川水电站地下厂房岩壁吊车梁岩台超挖严重问题,综合考虑现场地质状况、开挖现状、施工条件以及后续开挖可能进一步加剧围岩劣化等因素,对岩台超挖部分实施混凝土回填,并与岩壁吊车梁同期施工。通过建立岩壁吊车梁和回填混凝土及围岩三维有限元数值模型,计算分析了洞室下部开挖过程中的洞壁应力释放和桥机轮压、受拉锚杆注浆时机对岩壁吊车梁受拉锚杆应力以及壁吊车梁应力影响。结果表明:岩壁吊车梁锚固锚杆应力主要受洞壁应力释放影响,轴向拉应力最大值位于岩体中,桥机轮压影响幅度仅为0.32~3.15 MPa;岩壁梁锚固锚杆不宜与系统锚杆同时注浆。岩壁吊车梁运行状态良好,满足稳定要求。

白鹤滩水电站地下厂房排水系统特点及可靠性分析

基于白鹤滩水电站地下厂房排水系统结构及其特点进行可靠性分析,采用集水井集中排水的方式,结合排水量大小,充分考虑电站的长期稳定运行工况,选择型号合适的排水泵,既具备较好的排水功能,又尽量减少了岩体的开挖量。并对水淹厂房的意外应急措施进行了可行性分析,为后期运维提供充分准备,可供大型水电站地下厂房排水系统设计借鉴。

高地应力下双江口地下厂房围岩破坏特征及影响因素分析

双江口水电站作为大渡河流域水电梯级开发的上游控制性重点水库工程,受深山峡谷地域条件影响,地下厂房存在埋深大且地应力高的工程特点。以主厂房为研究对象,统计归纳了爆破开挖中现场围岩变形及破坏特征,并阐释了高地应力条件下岩体破坏机制及影响因素。研究结果表明,双江口水电站地下厂房爆破开挖过程中围岩主要发生板裂、板片状破裂、V型破裂以及应力与结构协同作用破坏四种主要类型。其中,板状破裂主要发育在边墙、顶拱及掌子面;板片状破裂和V型破裂主要发育在拱肩部位,破裂深度一般大于40 cm;应力与结构协同破坏围绕断层或节理聚集区,破坏规模不等且可预见性较差。

改性环氧灌浆料在水电站地下厂房渗水修补中的应用研究

水电站地下厂房是其关键性的建筑物,若是在施工或者设计环节出现问题导致渗漏,就会对水电站厂房的使用年限、功能产生影响。地下厂房渗漏水主要为厂房周围墙、底板地基出现渗漏,前者还包括孔洞、砼蜂窝渗漏。环氧树脂灌浆材料则是对从基础防渗强化、砼裂缝应用颇为广泛的灌浆材料,相较于溶剂型环氧灌浆材料而言,水性环氧灌浆材料优点更为突出,呈现出可以用水进行清洗,运用具有安全性,气体较少,挥发性颇低等。按照环保要求,该水化材料的应用前景更为广阔。

长垂直母线热压耦合厂房通风研究

大型地下电站发电机引出大多采用长垂直离相封闭母线(IPB),但在长垂直条件下因高度差产生的“烟囱效应”会导致母线上下温差过大,甚至超过母线最大运行工况下的温升限值,带来一定的安全隐患,并限制了地下电站封闭母线引出方式的运用。结合三峡地下电站等长垂直、大电流封闭母线竖井的特点,对长垂直封闭母线在不同影响因素下的热平衡特性进行了理论分析与数值计算。通过工程实践,探索出长垂直母线热平衡和地下厂房母线竖井通风的耦合模型及规律,并在此基础上提出了基于“热压耦合”的长垂直离相封闭母线的应用与通风设计的新思路。

深埋地下洞室动态安全监测设计——以白鹤滩右岸地下厂房为例

针对白鹤滩水电站右岸地下厂房的地质情况、结构布置以及变形和应力分布特点,从监测断面布置、监测手段选择、重点监测部位等方面着眼,建立起一套包括地下厂房围岩变形、支护结构应力、错动变形、岩壁吊车梁应力与变形等监测项目在内的深埋地下洞室监测系统,对重点监测部位和不良地质洞段,提出专门监测方案并实施自动化监测,同时根据开挖揭示和反馈分析,及时进行动态设计,达到预警预报以及指导施工等。实施结果表明该监测系统对指导工程安全施工及运行起到了重要作用。

抽水蓄能电站地下厂房岩壁吊车梁开挖爆破试验研究

针对抽水蓄能电站地下厂房岩壁吊车梁开挖技术,文章以河南某抽水蓄能电站为背景,结合厂房地质条件及岩壁吊车梁结构特点,通过开展现场爆破试验确定爆破参数,确保该部位的开挖质量满足设计及规范要求。结果对比表明:选择装药密度65g/m作为岩壁吊车梁开挖爆破参数,半孔率94.3%,局部最大超挖4cm,岩台完整且平整度控制良好。试验结果可为抽水蓄能电站岩壁吊车梁开挖施工提供工程实例和技术参考。

精细化管理在绩溪蓄能电站岩壁梁施工中的应用

岩壁梁是地下厂房开挖施工中难度和质量要求最高的部分。融入精细化施工理念于绩溪水电站地下厂房岩壁梁施工中,通过合理分层、规划开挖顺序及对各道关键工序的精密把控和调整,总结岩壁梁开挖操作要点,实现对岩台开挖过程的质量控制,完善岩壁梁开挖阶段的安全监测与保护措施,确保精细化管理在绩溪水电站地下厂房岩壁梁开挖过程中取得了良好的应用效果,保障了工程的开挖质量。

旭龙水电站地下厂房主要工程地质问题分析

通过分析潜在工程地质问题,为旭龙水电站地下厂房围岩支护设计提供地质依据,应用现场调查、室内外试验和三维数值模拟相结合的方法,对地下厂房围岩稳定问题及相应机理进行了深入分析。结果表明:围岩以花岗岩等硬岩为主,岩石类别主要为Ⅱ类,少量Ⅲ类。潜在工程地质问题主要包括不稳定块体、缓倾角结构面、小夹角长大结构面、局部高地应力、洞室涌水等,可能引起局部围岩片帮、掉块、崩落或塌方等变形破坏;大方量不稳定块体可能导致部分洞段整体失稳;洞室涌水会降低局部围岩稳定性,不利于施工。研究成果明确了旭龙水电站地下厂房主要工程地质问题,为围岩开挖和支护设计提供了理论支持。

大型抽水蓄能电站地下厂房岩锚梁施工技术

清原抽水蓄能电站通过对岩锚梁岩台爆破开挖、锚杆安装及混凝土施工等质量工艺的精细化管控,岩锚梁开挖轮廓成型规整,锚杆质量符合设计标准,混凝土质量综合评价为优良,满足电站安全稳定运行要求,其成果为国内地下厂房岩锚梁施工提供了工程实例和技术经验。

抽水蓄能电站地下厂房监测设计浅析

目前,抽水蓄能电站地下厂房监测设计无专门的设计规范,笔者结合相关设计规范及手册,总结十余座抽水蓄能电站地下厂房监测设计工程实践,提出厂房系统安全监测设计的目的和原则,以及围岩、支护结构、岩壁吊车梁等部位的监测设计方法,为抽水蓄能电站地下厂房安全监测设计提供参考。

复杂工况下地下厂房三维动力响应特性及安全评价

为了得到复杂工况下地下厂房的真实动力响应,考虑地下厂房结构、边界条件和受力特性的复杂性,采用三维动力有限元法开展地下厂房的动力特性分析。计算成果表明:动位移最大值发生在地下厂房的两侧,但各方向的动位移相对都比较小,说明良好的约束可以有效的减小振动位移;正常工况的动力系数比较小,基本上呈静态响应,其他工况的动力系数相对较大,不会发生共振;不同荷载组合下的结构振幅能满足规范设计要求。其成果为有效优化地下厂房整体动力特性、改进抗振设计提供了技术手段。