基于浆液–岩体耦合效应的微裂隙岩体注浆理论研究

在微裂隙岩体注浆工程中,浆液–岩体耦合效应对注浆扩散过程影响显著。基于宾汉流体浆液本构模型并引入两阶段裂隙变形控制方程,建立考虑浆–岩耦合效应的裂隙注浆扩散理论模型。利用质量守恒条件实现浆液扩散锋面追踪与注浆流量分配,通过试错法实现压力场与速度场的迭代求解,建立可完整描述注浆扩散过程的步进式算法。利用所创建的理论模型及步进式算法,分析浆液压力场及裂隙开度的分布规律,并从浆液扩散半径、裂隙变形所吸收的浆液量两个方面分析不同裂隙开度条件下浆–岩耦合效应对裂隙注浆扩散过程的影响程度。研究结果表明:在微裂隙岩体注浆工程中,裂隙宽度越小,浆–岩耦合效应对注浆扩散过程的影响越显著,注浆压力取代裂隙初始隙宽成为影响浆液扩散半径的主控因素。最后结合青岛地铁花岗岩微裂隙注浆工程实例验证了理论模型及步进式算法的正确性。     

地下工程涌突水注浆止水浆液扩散机制和封堵方法研究

 涌突水是地下工程的主要地质灾害之一。实践表明,注浆是治理涌突水的有效技术手段,但相关的动水注浆理论发展尚不成熟,尤其是裂隙动水条件下的浆液扩散和封堵机制研究不足。针对上述问题,研发准三维裂隙动水注浆模型试验台,进行裂隙岩体涌突水的动水注浆模型试验研究,通过对200余组试验数据进行分析,提出浆液的U形扩散规律和水泥浆液的分层分区扩散机制,得到浆液的快速析水沉积原理和沉积留核扩散规律,实现浆液扩散和封堵效果的定量评价。在此基础上,形成以浆水流量比为核心控制因素的裂隙涌水注浆封堵方法。室内涌水注浆封堵试验和龙固煤矿高压涌水现场注浆封堵试验进一步验证研究成果的正确性,这对发展动水注浆理论和指导工程实践有一定作用。     

厦门翔安海底隧道富水砂层注浆试验

 针对我国第一条海底隧道——厦门翔安海底隧道富水砂层段进行注浆试验，采用钻孔取芯和压水的方法对注浆效果进行检验，摸索该条件下的一些注浆规律，提出注浆量、注浆压力、注浆速度、扩散半径等注浆参数。通过试验研究海水对浆液强度的影响。研究结果表明，海水延长初凝时间、减缓浆液强度上升的速度、稀释浆液并加剧不均匀扩散。结合翔安海底隧道施工注浆的经验可以得出，以上几个问题是在海水注浆中值得深入研究的，其研究结果可为厦门海底隧道注浆的设计、施工提供指导，并可为相关工程提供重要的参考。     

基于黏度时变性的水泥–玻璃浆液扩散机制研究

工程地质灾害治理中,注浆是最常用的方法,浆液的扩散运移规律对工程设计和施工具有重要的意义。采用SV振弦式黏度计测定水泥–玻璃(C-S)浆液的黏度时变性,通过函数拟合获得黏度函数曲线;采用广义宾汉流体本构方程,推导C-S浆液在单一平板裂隙中的压力分布方程;通过平板裂隙注浆模拟试验研究,分析定注浆流量条件下的C-S浆液扩散的压力场分布规律;运用数值计算方法,研究定注浆速率条件下的浆液扩散形态及压力场时空变化规律。结合理论分析、模拟试验和数值计算结果分析C-S浆液扩散机制,希望能够为C-S浆液的工程应用提供一定的借鉴。     

裂隙岩体注浆中的浆液–岩体耦合效应分析

基于岩体卸荷–加载理论与平板裂隙浆液运移方程,建立考虑浆液对岩体单向耦合作用的裂隙岩体注浆理论模型,对注浆过程中浆液与围岩的相互作用展开研究。研究表明,裂隙岩体注浆伴随着浆液压力对岩体卸荷与重新加载过程,岩体完全卸荷后,隙宽将随浆液压力增加,对于近似水平展布的裂隙,隙宽增量随扩散距离近似呈线性衰减,裂隙越小衰减速率越快。岩体受浆液卸荷影响范围大于浆液扩散范围,裂隙越小受浆液–岩体耦合作用越显著。裂隙组中相邻的裂隙在注浆过程中相互影响,较大裂隙进一步张开,较小裂隙趋于闭合,导致浆液在微小裂隙中的扩散范围减小或无法注入,并在较大裂隙中大量无效扩散,单纯提高注浆压力不会改善对较小裂隙的注浆封堵效果。研究结论对裂隙岩体注浆工程提供了一定指导与借鉴。     

基于牛顿流体的海底隧道穿越裂隙岩体注浆扩散半径计算

在分析胶州湾海底隧道注浆方案及浆液特性的基础上,采用牛顿流体类的刘嘉才公式进行裂隙岩体注浆扩散半径计算。计算结果表明:当设计注浆压力为3～4MPa、注浆孔半径为5cm和注浆时间为1800～3600s时,浆液的扩散半径能满足设计要求;浆液的扩散半径随着注浆时间的增加而增大,在注浆时间相同时,浆液的扩散半径随着裂隙宽度的减小而减小;浆液的扩散半径随着注浆压力的增加而增大,但在注浆压力相同时,浆液的扩散半径随着裂隙宽度的减小而减小。     

岩体裂隙网络注浆模拟试验系统研制及应用

为研究浆液在岩体裂隙网络内的扩散迁移规律,研制了可视化裂隙恒压注浆试验系统。该系统由供压设备、恒压出浆设备、裂隙模拟设备以及监测设备组成,可根据试验要求设计特定岩体裂隙网络,模拟不同注浆压力、浆液黏度、裂隙开度等多种参数影响下的浆液流动过程,并可研究裂隙岩体中浆液-水/气驱替作用机制。通过单一裂隙注浆理论与试验结果的对比,验证本试验系统的可靠性。基于此,进一步研究随机裂隙网络注浆扩散机制,结果表明:(1)裂隙内同一点压力随注浆压力的增大而增大,随裂隙开度的增大而减小,不随浆液黏度的变化而变化;(2)浆液在裂隙网络内由总流分散为支流后,压力显著下降,流速放缓,且各支流压力与流量分配系数受交叉(分叉)裂隙夹角影响较大。试验系统的研制及研究成果对岩体工程注浆具有一定指导价值。     

围岩性质对于注浆压力变化规律及浆液扩散模式的

采用注浆模拟试验及理论分析研究了围岩性质对于注浆压力变化规律及浆液扩散模式的影响。试验采用在注浆模型架内分区充填不同孔隙比土体的方法模拟被注围岩显著的向异性及非均质性;采用多个注浆管依次注浆的方法模拟实际注浆工程中的不同注浆施工阶段。通过开挖揭露浆脉(浆泡)特征研究围岩性质对于浆液扩散形式的影响;通过分析注浆过程中注浆压力数据研究围岩性质对于注浆压力的影响;通过对注浆前后围岩试样进行室内试验测试,获取注浆对于围岩孔隙比及压缩系数的影响规律。研究结果证实：注浆压力变化规律及浆液扩散模式与围岩性质密切相关,通过分析注浆压力变化规律与浆液扩散模式可判定围岩性质,从而为注浆施工过程中的注浆参数动态调整提供依据。相关研究结论在永莲隧道帷幕注浆工程中进行了现场试验,进一步验证了其正确性。     

围岩性质对于注浆压力变化规律及浆液扩散模式的影响研究

采用注浆模拟试验及理论分析研究了围岩性质对于注浆压力变化规律及浆液扩散模式的影响。试验采用在注浆模型架内分区充填不同孔隙比土体的方法模拟被注围岩显著的向异性及非均质性;采用多个注浆管依次注浆的方法模拟实际注浆工程中的不同注浆施工阶段。通过开挖揭露浆脉(浆泡)特征研究围岩性质对于浆液扩散形式的影响;通过分析注浆过程中注浆压力数据研究围岩性质对于注浆压力的影响;通过对注浆前后围岩试样进行室内试验测试,获取注浆对于围岩孔隙比及压缩系数的影响规律。研究结果证实:注浆压力变化规律及浆液扩散模式与围岩性质密切相关,通过分析注浆压力变化规律与浆液扩散模式可判定围岩性质,从而为注浆施工过程中的注浆参数动态调整提供依据。相关研究结论在永莲隧道帷幕注浆工程中进行了现场试验,进一步验证了其正确性。     

考虑重力和黏度时变性的隧道围岩水泥浆液扩散规律研究

浆液重力和黏度时变性对浆液有效扩散范围及扩散形态的影响显著,而浆液扩散范围对隧道安全性起着决定性的作用。基于流固耦合理论和渗流力学理论建立了考虑浆液重力与黏度时变性耦合效应下的注浆浆液扩散方程,依托多物理场耦合软件COMSOL Multiphysics实现了在建旧寨隧道工程中风化板岩管棚注浆扩散过程的数值模拟,并由此分析了注浆压力、浆液黏度时变性与注浆时间对浆液有效扩散范围及注浆加固圈形成的影响规律。研究结果表明：考虑水泥浆液重力后,浆液在岩土体中的扩散形态呈椭球型,注浆压力越小且注浆时间越长,浆液重力对扩散形态的影响越显著;在注浆孔水平面以上浆液扩散范围远小于注浆孔水平面以下浆液扩散范围,且在注浆孔左、右两侧浆液扩散范围呈对称分布,与重力作用机制相符;浆液黏度时变性对浆液扩散距离的影响效果显著;注浆加固圈的分布形态与注浆管的埋设角度密切相关,注浆管埋设角度越小,注浆加固圈的厚度越大,合理布设小导管是获得有效注浆加固圈的关键。     

Numerical evaluation of strength and deformability of fractured rocks

Knowledge of the strength and deformability of fractured rocks is important for design, construction and stability evaluation of slopes, foundations and underground excavations in civil and mining engineering. However, laboratory tests of intact rock samples cannot provide information about the strength and deformation behaviors of fractured rock masses that include many fractures of varying sizes, orientations and locations. On the other hand, large-scale in situ tests of fractured rock masses are economically costly and often not practical in reality at present. Therefore, numerical modeling becomes necessary. Numerical predicting using discrete element methods(DEM) is a suitable approach for such modeling because of their advantages of explicit representations of both fractures system geometry and their constitutive behaviors of fractures, besides that of intact rock matrix. In this study, to generically determine the compressive strength of fractured rock masses, a series of numerical experiments were performed on two-dimensional discrete fracture network models based on the realistic geometrical and mechanical data of fracture systems from feld mapping. We used the UDEC code and a numerical servo-controlled program for controlling the progressive compressive loading process to avoid sudden violent failure of the models. The two loading conditions applied are similar to the standard laboratory testing for intact rock samples in order to check possible differences caused by such loading conditions. Numerical results show that the strength of fractured rocks increases with the increasing confning pressure, and that deformation behavior of fractured rocks follows elasto-plastic model with a trend of strain hardening. The stresses and strains obtained from these numerical experiments were used to ft the well-known Mohr-Coulomb(MC) and Hoek-Brown(H-B) failure criteria, represented by equivalent material properties defning these two criteria. The results show that both criteria can provide fair estimates of the co     

Thermally induced mechanical and permeability changes around a nuclear waste repository—a far-field study based on equivalent properties determined by a discrete approach

A numerical investigation is conducted on the impacts of the thermal loading history on the evolution of mechanical response and permeability field of a fractured rock mass containing a hypothetical nuclear waste repository. The geological data are extracted from the site investigation results at Sellafield, England.A combined methodology of discrete and continuum approaches is presented. The results of a series of simulations based on the DFN–DEM (discrete fracture network–distinct element method) approach provide the mechanical and hydraulic properties of fractured rock masses, and their stress-dependencies. These properties are calculated on a representative scale that depends on fracture network characteristics and constitutive models of intact rock and fractures. In the present study, data indicate that the large scale domain can be divided into four regions with different property sets corresponding to the depth. The results derived by the DFN–DEM approach are then passed on to a large-scale analysis of the far-field problem for the equivalent continuum analysis.The large-scale far-field analysis is conducted using a FEM code, ROCMAS for coupled thermo-mechanical process. The results show that the thermal stresses of fractured rock masses vary significantly with mechanical properties determined at the representative scale. Vertical heaving and horizontal tensile displacement are observed above the repository. Observed stress and displacement fields also shows significant dependency on how the mechanical properties are characterized. The permeability changes induced by the thermal loading show that it generally decreases close to the repository. However, change of permeability is small, i.e., a factor of two, and thermally induced dilation of fracture was not observed. Note that the repository excavation effects were not considered in the study.The work presented in this paper is the result of efforts on a benchmark test (BMT2) within the international co-operative projects DECOVALEX III and BENCHPAR.     

Numerical determination of the equivalent elastic compliance tensor for fractured rock masses using the distinct element method

The purpose of this paper is to establish a methodology to determine the equivalent elastic properties of fractured rock masses by explicit representations of stochastic fracture systems, and to investigate the conditions for the application of the equivalent continuum approach for representing mechanical behavior of the fractured rock masses. A series of numerical simulations of mechanical deformation of fractured rock masses at different scales were conducted with a large number of realizations of discrete fracture networks (DFN), based on realistic fracture system information and using the two-dimensional distinct element program, UDEC. General theory of anisotropic elasticity was used for describing the macroscopic mechanical behavior of fractured rock masses as equivalent elastic continua. Verification of the methodology for determining the elastic compliance tensor was conducted against closed-form solutions for regularly fractured rock mass, leading to very good agreements. The main advantage of the developed methodology using the distinct element method is that it can consider complex fracture system geometry and various constitutive relations of fractures and rock matrix, and their interactions. Two criteria for the applicability of equivalent continuum approach were adopted from the investigations: (i) the existence of a properly defined REV (representative elementary volume) and (ii) the existence of an elastic compliance tensor. For the problems with in situ conditions studied in this paper, the results show that a REV can be defined and the elastic properties of the fractured rock mass can be represented approximately by the elastic compliance tensor through numerical simulations.     

Numerical calculations for prediction of grout spread with account for filtration and varying aperture

Grouting as a mean to reduce the ingress of water to underground facilities has been used for decades. With an increased demand for tightness and cost efficiency, the incentive to improve the method has also increased, and the need to understand the governing factors has been focused. The knowledge concerning grouting involves several fields of research, for instance flow in fractured rock and the behaviour of the grouting material. An understanding of these fields is essential in grouting research. Numerical modelling of grout propagation in fracture geometries is one means of achieving such understanding. The paper presents how numerical calculations of grout spread and sealing effect can be used for predictions of the grouting result. The calculation concerns flow of grout in a network of conductive elements, representing a fracture geometry with the scope to understand the governing parameters when grouting. The spread of grout is significantly affected by the spatial variability of the fracture aperture. Measurements on grout properties and laboratory experiments show that the grout possesses a limited penetration ability and that filtration of the grout occurs if the aperture of a constriction is smaller than a critical value, i.e. when a filter cake forms in front of constrictions in the flow and the grout that passes is filtered. In the paper, a model for filtration of grout is presented. When filtration and limited penetration ability are incorporated in the calculations, additional strong effects are observed. This underlines the need of both a representative geometry, including the fracture variability, and measurements of grout properties.     

基于有限元方法的裂隙岩体等效强度参数研究

 利用等效连续介质力学方法分析裂隙岩体中工程稳定性时,选择合理的裂隙岩体等效强度参数是取得可靠分析结论的前提。依据建立的裂隙岩体网格,结合岩石统计损伤模型和结构面损伤模型,通过有限元数值方法研究裂隙岩体加载中的渐进破坏过程,以及裂隙岩体等效抗压强度的尺寸效应和各向异性。分析结果表明,从岩块到岩体,岩体等效抗压强度很快降低至稳定幅度,岩体抗压强度的各向异性也不显著。最后,对10 m尺寸的岩体进行不同围压下抗压强度的数值分析,得到裂隙岩体的强度参数,并和Hoek-Brown经验准则进行对比。文中的分析方法对于工程裂隙岩体的宏观参数取值具有参考价值。     

裂隙岩体非饱和渗流本构关系

基于连续介质的方法，通过裂隙非饱和渗流的二维数值模拟，对裂隙岩体非饱和渗流中应用Van Genuchten(VG)模型和Brooks-Corey(BC)模型进行评价并建立了改进的本构关系。VG模型虽然可以与持水曲线匹配得很好，但是VG模型和BC模型都对相对渗透率估计过低。模拟结果表明：改进的BC相对渗透率-饱和度的关系和VG毛管压力-饱和度的关系结合，可以较好地描述非饱和渗流的本构关系。     

裂隙岩体渗流–损伤–断裂耦合模型及其应用

 从岩体结构力学和细观损伤力学的角度出发,根据裂隙发育与工程尺度的关系,建立合理且适用的裂隙岩体渗流–损伤–断裂耦合数学模型,该模型能真实反映渗流场与应力场耦合作用下裂隙岩体的损伤演化特性,并能模拟由于渗透压的存在和变化引起的拟连续岩体内翼形裂纹的开裂、扩展和贯通等损伤演化特性和高序次贯通裂隙的张开、闭合。建立考虑渗透压力的三维含水裂隙岩体弹塑性断裂损伤本构方程和损伤应力状态作用下流体渗流方程,给出该数学模型的求解策略与方法,开发裂隙岩体渗流–损伤–断裂耦合分析的的三维有限元计算程序DSDFC.for。该计算程序能模拟岩体分步开挖、应力和渗流边界的动态变化,对裂隙岸坡蓄水加载过程进行渗流–损伤–断裂耦合分析,发现水库蓄水后岸坡山体的竖向抬升,随水位上升岸坡破损区增大,断层塑性区向岸坡深部扩展,与裂隙渗流比较,拟连续岩体渗流滞后。     

黄岛地下水封洞库库区三维裂隙网络模拟

 低渗透性的裂隙岩体是地下水封石油洞库建库的最佳选址区,裂隙网络模拟技术是研究离散裂隙渗流的有效手段。以黄岛地下水封洞库库区渗透性研究为出发点,在地表裂隙调查与钻孔裂隙统计的基础上,运用离散裂隙模拟软件DFN对洞库区进行三维裂隙网络模拟,得出模拟区导水系数分布图以及ZK13钻孔连通性分布图,通过将模拟结果与野外试验结果对比,认为模拟结果合理可信。实例分析表明,模拟结果能较为深刻地揭示裂隙水渗流的本质,可为后续的洞库水封效果及涌水量评价提供参考。     

Determination of three dimensional hydraulic conductivities using a combined analytical/neural network model

Analysis of groundwater flow through fractured rock masses is an essential step in many engineering and environmental problems, such as in safety assessment of radioactive waste storages, hydrocarbon storage caverns and hydropower projects. The most important hydrological parameter in groundwater flow analysis is the hydraulic conductivity which is anisotropic and heterogeneous in the fractured rock masses. To analyze the groundwater flow correctly, some site investigations through boreholes must be carried out. One of the challenges in seepage analysis for an engineering project is how to determine the anisotropic and heterogeneous hydraulic conductivities of the fractured rock masses using the limited in situ investigation data. In this study, a new practical approach for the determination of three dimensional hydraulic conductivities of fractured rock masses is presented. Starting from rock fracture properties surveyed in six boreholes, the anisotropic hydraulic conductivities are estimated using the in situ injection test results and Oda’s theoretical model. A neural network method is then utilized to generate the three dimensional heterogeneous hydraulic conductivities based on the anisotropic hydraulic conductivities along the six boreholes. In order to evaluate the reliability of this approach, a 3D numerical seepage model using code FLAC3D is performed for a real project. The inflow values in a shaft obtained with the 3D numerical analysis are compared with the in situ measured flow. The result indicates that the derived hydraulic conductivity is acceptable.     

Effects of fracture distribution and length scale on the equivalent continuum elastic compliance of fractured rock masses

fracture systems have strong influence on the overall mechanical behavior of fractured rock masses due to their relatively lower stiffness and shear strength than those of the rock matrix.Understanding the effects of fracture geometrical distribution,such as length,spacing,persistence and orientation,is important for quantifying the mechanical behavior of fractured rock masses.The relation between fracture geometry and the mechanical characteristics of the fractured rock mass is complicated due to the fact that the fracture geometry and mechanical behaviors of fractured rock mass are strongly dependent on the length scale.In this paper,a comprehensive study was conducted to determine the effects of fracture distribution on the equivalent continuum elastic compliance of fractured rock masses over a wide range of fracture lengths.To account for the stochastic nature of fracture distributions,three different simulation techniques involving Oda's elastic compliance tensor,Monte Carlo simulation(MCS),and suitable probability density functions(PDFs) were employed to represent the elastic compliance of fractured rock masses.To yield geologically realistic results,parameters for defining fracture distributions were obtained from different geological fields.The influence of the key fracture parameters and their relations to the overall elastic behavior of the fractured rock mass were studied and discussed.A detailed study was also carried out to investigate the validity of the use of a representative element volume(REV) in the equivalent continuum representation of fractured rock masses.A criterion was also proposed to determine the appropriate REV given the fracture distribution of the rock mass.