一种理想自膨胀浆液单裂隙扩散模型

为研究自膨胀浆液在岩体裂隙中的扩散机制,以一种已知密度随时间变化规律的理想自膨胀浆液为对象,基于黏性流体力学理论,考虑浆液初始充填范围、裂隙开度、时间、膨胀系数等因素的影响,推导无水条件下浆液在平面单裂隙中的径向扩散模型,并结合典型工况,采用通用CFD软件Fluent建立相应的轴对称分析模型,对该理论模型进行数值验证,结果显示,不同工况下求解得到的不同时刻浆液扩散半径、压力、流速分布等结果与解析解吻合良好,从而证明了所推导扩散模型的合理性与正确性。该模型的提出对于自膨胀浆液裂隙注浆理论研究具有一定参考价值。     

基于SVR的灌浆结石体强度回归预测分析

灌浆是增强地层强度、防止地基沉降和变形的工程方法 ,灌浆结石体强度是反应灌浆效果的主要因素,而灌浆结石体强度又受到浆液水灰比、浆液粘度、灌浆压力、粒径和曲率系数等因素的影响。应用支持向量回归机(SVR)对试验所得灌浆结石体强度进行回归分析,研究结果显示,浆液粘度增大结石体强度增大;介质粒径增大结石体强度降低;灌浆压力增大结石体强度增大;可运用SVR模型确定不同结石体强度下的灌浆参数。     

速凝浆液裂隙动水注浆扩散数值模拟与试验验证EI北大核心CSCD

针对动水注浆中常用的2种速凝浆液,水泥–水玻璃浆液与高聚物改性水泥浆液,考虑浆液黏度时变特性,应用有限元计算软件COMSOL Multiphysics建立动水条件下裂隙注浆扩散的数值模型,研究动水条件下裂隙注浆扩散规律并分析不同黏度时变特性、初始动水流速与注浆速率对注浆扩散过程的影响,并将数值模拟结果与模型试验进行对比,验证数值模拟方法的有效性。研究结果表明:浆液扩散形态在逆水方向和顺水方向表现出明显的差异性;进水边界处的压力逐渐趋近于远端的地下水压强,注浆初期在裂隙边界附近及绕流区内流速较高,注浆后期整个裂隙内的流速变化幅度不大;在试验条件下,初始动水流速与注浆速率的提高均会导致裂隙内压力及流速的增加,注浆速率对裂隙内压力分布的影响比初始动水流速显著;C-S浆液与GT–1浆液扩散规律类似,但由于两者黏度时变性的差异导致两者扩散规律稍有差别。     

速凝浆液裂隙动水注浆扩散数值模拟与试验验证

针对动水注浆中常用的2种速凝浆液,水泥–水玻璃浆液与高聚物改性水泥浆液,考虑浆液黏度时变特性,应用有限元计算软件COMSOL Multiphysics建立动水条件下裂隙注浆扩散的数值模型,研究动水条件下裂隙注浆扩散规律并分析不同黏度时变特性、初始动水流速与注浆速率对注浆扩散过程的影响,并将数值模拟结果与模型试验进行对比,验证数值模拟方法的有效性。研究结果表明:浆液扩散形态在逆水方向和顺水方向表现出明显的差异性;进水边界处的压力逐渐趋近于远端的地下水压强,注浆初期在裂隙边界附近及绕流区内流速较高,注浆后期整个裂隙内的流速变化幅度不大;在试验条件下,初始动水流速与注浆速率的提高均会导致裂隙内压力及流速的增加,注浆速率对裂隙内压力分布的影响比初始动水流速显著;C-S浆液与GT–1浆液扩散规律类似,但由于两者黏度时变性的差异导致两者扩散规律稍有差别。     

深隧调蓄系统中入流竖井内部流场的数值模拟

入流竖井是城市深隧调蓄系统与浅层排水系统衔接的关键部件,竖井内部流场直接影响竖井的消能、控声、排气功能,进而影响深隧系统的正常运转。为此,利用FLUENT软件中的RNG k-ε湍流模型,对跌落式入流竖井内部流场进行了数值模拟,计算了不同竖井体型和不同入口流速工况下竖井内部压力场、速度场的变化规律以及竖井的消能率。结果表明,入口流速的变化对下方渐缩管和消能管下侧的压力影响较大,低流速工况对消能管的压力较大、高流速工况对渐缩管的压力较大,入口流速的增加会导致消能管消能效果的下降;另外,适当增加消能管长度可有效提高消能效果和出水稳定性。     

砂土注浆的颗粒流细观力学数值模拟

灌浆工程隐蔽性较强,浆液扩散机理远不成熟。基于细观力学理论的PFC2D数值仿真试验技术,可以从细观角度研究灌浆过程中土颗粒的位移、变形运动及与浆液的耦合作用过程,为注浆机理研究开辟了一条新的途径。基于流固耦合原理的PFC2D颗粒流数值模拟程序,运用其内置FISHTANK函数库和FISH语言,分别定义流体域的流动方程和压力方程,对灌浆过程中浆液在地层中的扩散过程和形态进行了数值模拟计算。通过调节PFC命令流中的注浆压力、时间步长、水力传导系数等参数对浆液的注浆过程进行了模拟计算。模拟结果表明,灌浆过程中浆液与地基土的作用形式与灌浆压力大小密切相关,为达到理想的劈裂灌浆效果需要适当提高注浆压力,但过高注浆压力会对地层结构造成一定的破坏。对钻孔周围土体的应力状态进行了理论推导和分析,指出土体环向拉应力的增加导致钻孔周围产生劈裂缝,浆液由渗透作用方式向劈裂作用方式转变,数值模拟结果与理论推导结果相符。劈裂灌浆作用发生时,孔隙率和应变率均增加。流动性能差的稠浆适于压密灌浆和劈裂灌浆,流动性能好的稀浆则适于渗透性灌浆,而浆液的渗透性能对高压劈裂灌浆的作用效果影响不明显。     

全风化花岗岩地层脉动灌浆控制防渗机理研究

针对全风化花岗岩地层的基础防渗加固,传统灌浆工艺限制于结构松散难以成孔起压,加剧了地基处理的难度。提出采用"钻灌一体,脉动灌浆"技术工艺;并利用数值模拟实现了不同脉动周期压力、钻灌时间控制参数下浆液渗透扩散规律及脉动周期压力下地层应力–应变的过程分析,通过脉动和稳压灌浆的浆液扩散与防渗影响范围对比,揭示了脉动灌浆防渗控制机理,得出了灌浆参数;结合黏土水泥浆灌浆材料进行了现场工程试验,现场试验验证了控制参数的合理性。试验表明,1.5~2.0 MPa脉动灌浆压力下,单排孔布设间距1 m,常规吕荣试验检查孔段次统计,透水率<2 Lu的占70%;疲劳吕荣试验透水率<3 Lu的比例为97%,透水率稳定区间为0.5~2.4 Lu;破坏吕荣试验透水率稳定区间为2~8.5Lu。灌浆后全风化、强风化地层的岩体完整性均有不同程度的提高,声波提升幅度范围为17.3%~52.5%。检查孔取出的芯样较完整,芯样抗压强度平均达7.3 MPa,且灌浆过程地层抬升小。研究成果对于全风化花岗岩以及同类地层具有较强的应用性,为此类地层防渗处理提供了一个可借鉴的工程案例。     

劈裂灌浆扩散机理研究

劈裂灌浆在实际工程中应用相当广泛。由于影响浆液扩散的因素众多,劈裂灌浆扩散机理尚不明确,尤其是不同给压方式(稳压和脉动)对浆液扩散的影响研究很少,对这两种方式下的劈裂灌浆机理进行了探讨。对于稳压灌浆方式,基于水力劈裂缝的扩展形态来考虑浆液的运动,视劈裂注浆扩散形态为平面辐射椭圆,采用恒缝高矩形断面模型,推导出宾汉流体的劈裂灌浆扩散方程,并分析了灌浆压力、浆材黏度、土体弹性模数、劈裂通道宽度对浆液扩散范围的影响。对于脉动灌浆方式,由于施加给受灌体荷载的延滞效应和脉动叠加作用,多次脉动灌入的浆液会使劈裂通道宽度逐渐增大,采用扁球体的劈裂灌浆模型,推导出脉动方式时的浆液扩散方程,分析了脉动灌浆频率等与浆液扩散距离的相互关系;结果表明,浆液的扩散距离与脉动频率的关系曲线存在一个极小值,发生在脉动频率为10 min次时,这一参数可作为脉动灌浆方式的控制参数。最后将前人的稳压灌浆模型与本文的脉动模型与相互比较,研究两种灌浆方式劈裂扩散机理的差异,得到脉动灌浆时浆液扩散距离要远短于稳压方式的,表明通过采用脉动灌浆,调节相关参数能有效控制浆材扩散范围,相关规律可为工程实际提供理论依据。     

非水反应型材料灌浆堵漏模型研究

灌浆是解决工程渗漏问题的重要技术手段,堵漏材料是灌浆技术的核心。水泥浆液、水泥膏浆、速凝膏浆、改性沥青、低热沥青等非水反应型浆液是最常用的堵漏材料。根据浆液流变性质、在宽大孔(裂)隙中的扩散方式和封堵机理以及灌浆工艺参数建立了非水反应型灌浆材料的堵漏模型,对不同浆液在不同开度、不同流速地层的堵漏效率和堵漏效果进行了计算分析,可以为非水反应型浆液在堵漏工程中的选择使用提供依据。     

膏浆平面裂隙动水注浆扩散模型研究

为探究膏浆平面大密度裂隙动水注浆扩散模型,首先以宾汉姆流体为研究对象,基于广义达西定律并运用相关力学理论,推导得出考虑膏浆自重的浆液扩散半径计算公式;其次,采用室内模型试验对浆液扩散半径计算公式进行验证,得出扩散半径试验值同理论公式计算值的误差小于10%。以地铁车站基坑堵漏工程为背景,根据浆液扩散半径计算公式,对不同参数进行单因素影响分析,结果表明,灌浆压力差、浆液屈服应力、裂隙半径对浆液扩散影响显著,扩散半径变化率大于60%;同时进行原位试验,对比得出扩散半径试验值同理论公式计算值误差小于10%。因此,在一定误差范围内,建立的扩散模型对平面大密度裂隙动水注浆工程具有指导意义。     

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。     

分形插值不规则断层的浆液扩散规律研究

为研究浆液在不规则断层内的扩散规律,基于自仿射分形插值曲面理论构建不规则断层,结合裂隙岩体注浆理论对断层形态、浆液黏度和注浆孔的布置对浆液扩散的影响进行了深入研究。研究结果表明：断层凹凸不平使得断层宽度呈随机分布,导致浆液呈非圆（柱）形扩散,不能依据浆液扩散半径公式来设计和布置注浆孔间距;在断层窄处,节点注浆压力等值线间距小,压力梯度大,反之亦然;浆液黏度越大,浆液所谓的惰性越强,扩散距离明显缩短,在断层注浆工程中,应结合浆液流变试验和浆液扩散数值分析成果,来优化浆液选型及配比。     

注浆扩散与浆液若干基本性能研究

浆液流型、流变参数的时变性、可灌性、塑性强度和可重复注浆性是影响浆液扩散的基本性能。试验表明,各种浆液分别属于三种不同流型;水泥基浆液在注浆过程中流型不变;浆液粘度的时变性规律符合指数函数。研制了平板裂隙注浆装置进行试验,结果表明,普通水泥浆的最小可灌裂隙宽度并非 0.18 mm 或 0.2 mm。在重复注浆时,后注浆液克服先注浆液的粘聚力,在流道中间冲开新通道继续注入,而不是推动先注浆液向前整体移动。“塑性强度”概念可以推广到一般浆液,用这一指标可以预知浆液的可注期。基于以上试验研究成果,尤其是粘度时变性规律,建立了稳定性浆液注浆扩散模型。     

考虑浆液自重的盾构隧道管片注浆浆液渗透扩散模型

为研究盾构隧道管片注浆的渗透扩散模型,以宾汉姆浆液流体为研究对象,基于广义达西定律(毛管组理论),并运用相关流体力学理论,推导了考虑浆液自重的盾构隧道管片注浆渗透扩散模型的计算公式,并分析了其适用范围及各参数的确定方法。结合具体计算案例,讨论了注浆参数(注浆压力、注浆时间)、地层特性(地层渗透系数)等主要因素对浆液扩散半径的影响及浆液对管片总压力的影响。结果表明:考虑浆液自重后,浆液的扩散范围呈椭球形;相同的注浆压力下,顶部注浆孔的浆液扩散范围小于底部注浆孔浆液扩散范围(顶部注浆孔出现最小扩散半径,底部注浆孔出现最大扩散半径);注浆压力、注浆时间及地层渗透系数增大,浆液扩散半径也增大,但其增长速率均减小;注浆压力增大,管片所受的注浆压力增大,单位管片所受的浆液压力呈线性增长,考虑浆液自重后,上部单位管片所受的浆液压力大于下部单位管片所受的浆液压力;注浆压力越大,注浆时间越长,地层渗透系数越大,最大扩散半径与最小扩散半径的差值越大,即浆液自重对浆液扩散半径的影响越大。     

Stop mechanism for cementitious grouts at different water-to-cement ratios

Cementitious grouts are the most commonly used grouting material in the world. The general concept of grouting is to propagate the grout in a sufficiently large volume in the grouted medium and hence to have a controlled penetration. This study has been performed in order to determine and test the different mechanisms that result in stoppage of the penetration of cementitious grouts. This is performed as sand column tests in a laboratory study, coupled with grouting in the field. The result shows that three different stop mechanisms can be identified depending on the ratio between the grain size of the grout and the available opening. At an opening up to three times the size of the largest grout grains, penetration does not occur due to clogging of the grains. For an opening larger than five times the largest grain the penetration is unrestricted and stoppage occurs due to equilibrium between the driving and resistance forces. Between these ratios, a transition area exists where the water content determines the penetrability and the stoppage is governed by a filtration process for the grout grains. This implies that grouting with higher water-to-cement ratios results in a larger penetration area and hence by applying the mixture-thickening method during grouting an increased sealing efficiency can be obtained.     

A robust method to determine the shear strength of cement-based injection grouts in the field

There is no standardised method to directly determine the shear strength of grouts in the field. Determining the shear strength would make it possible to calculate the penetration length of cement-based grouts and hence establish a design of the grouting procedure. By developing a new robust method that consists of a stick sinking in the grout, a direct measurement of the shear strength can be made, using the same set up as the separation test. The sink of the stick depends on the shear force interaction between the grout and the stick, and hence the shear strength of the grout can be determined. To verify the results, the shear strengths obtained with the stick are compared with measurements of the shear strength made with a rotational rheometer in the laboratory. The comparison shows good agreement; hence the stick can be used in the field to determine the yield strength of cement-based grouts.     

Effect of grout pressure and grout flow on soil physical and mechanical properties in jet grouting operations

Jet grouting is a method for improving soil characteristics. In this method, grouting of cement slurry with high pressure and velocity causes damage to soil structure. Excavated grains of soil are then removed from the borehole and are replaced with cement slurry. The grains that remain around the borehole mix with cement slurry and produce an improved soil mass of soil. This mass is called “soilcrete”. Soilcrete has special characteristics such as high strength, low deformability and very low permeability. The jet grouting process and its results are affected by various parameters of the soil material and jet grouting system. This paper discusses the effects of jet grouting process on the soil properties before and after the operations, and the effects of grout pressure and grout flow on soilcrete's uniaxial compression strength (UCS). For these purposes, five types of the laboratory tests have been done on the jet grouted soil: uniaxial compression, triaxial compression, direct shear, Brazilian indirect tension, and Schmidt hammer tests. According to the numerical results obtained from experiments, by increasing the grout pressure and flow, the UCS (MPa) of soil increases logarithmically. In addition, jet grouting dramatically increases properties such as cohesion and friction angle.     

Estimating the groutability of granular soils: a new approach

This paper evaluates different parameters that affect the grouting of soil, and presents a new approach to predict the groutability of granular soil. An accurate prediction of the groutability of granular soils has always been complicated due to the effects of different soil parameters. We know that these parameters are the grain-size of soil and cement-based grouts, the relative density and fine contents of soil, the water/cement ratio of grout mixture and grouting pressure, which directly affect the groutability of soil media. However, the relative density, fine contents of soil, the water/cement ratio, and grouting pressure are seldom considered as the prediction of groutability. In order to study the effects of the parameters on groutability, an alternative empirical formula to estimate the groutability of granular soils is presented in this paper and supported by experimental results obtained from the grouted sand samples prepared with various relative densities. The newly developed approach will help for the more accurate prediction of the groutability in granular soils and may also be used to provide first-hand information about the groutability of soils.     

流变参数时变性幂律型水泥浆液的柱形渗透注浆机制研究

 幂律型水泥浆液的流变参数时变性特征对注浆效果具有非常重要的影响。采用理论分析与实验研究等方法,研究了时变性幂律型水泥浆液的流变方程与渗流运动方程,推导了流变参数时变性幂律型水泥浆液的柱形渗透注浆扩散机制,分析了其适用范围及参数的确定方法,探讨了注浆管侧面注浆孔的设计依据。通过设计注浆试验对其进行了验证,结果表明：实际测量计算的幂律型水泥浆液在被注砾(砂)石体中的等效横向扩散半径值与由流变参数时变性幂律型水泥浆液的柱形渗透注浆扩散机制公式计算出的扩散半径理论值间虽有20%-30%范围内的差异,然它们都处于可接受的范围内;因此,能较好地说明幂律型水泥浆液在被注材料中随时间变化的柱形渗透注浆特征与规律。由于目前国际国内对流变参数时变性幂律型流体的柱形渗透注浆机制的研究还鲜有相关的文献报道,因此,本文研究成果可为实际注浆施工提供理论支撑与指导作用。     

Laboratory testing of chemical grouts

The range of chemical grout uses in civil and underground engineering has increased rapidly, along with requirements on special sealing and reinforcing grouting technologies with high target parameters. Connecting demands of knowledge of grout properties and behaviour during grouting process and after curing are necessary for the design and control of the grouting technologies. In the past, the laboratory research on grouts was mainly directed at concrete mixtures. Recently, the laboratory testing methods for chemical grouts have been developed; the methods are often different, and the chemical grouts used have different properties. The paper deals with methods used an developed in the laboratories of the Institute of Geonics in Ostrava, Czech Republic, and present the results of laboratory tests connecting to well-known projects in the Czech Repuvlic (e.g. underground gas storage Háje).