Discrete element simulation of mechanical characteristic of conditioned sands in earth pressure balance shield tunneling

The discrete element method (DEM) was used to simulate the flow characteristic and strength characteristic of the conditioned sands in the earth pressure balance (EPB) tunneling. In the laboratory the conditioned sands were reproduced and the slump test and the direct shear test of the conditioned sands were implemented. A DEM equivalent model that can simulate the macro mechanical characteristic of the conditioned sands was proposed,and the corresponding numerical models of the slump test and the shear test were established. By selecting proper DEM model parameters,the errors of the slump values between the simulation results and the test results are in the range of 10.3%-14.3%,and the error of the curves between the shear displacement and the shear stress calculated with the DEM simulation is 4.68%-16.5% compared with that of the laboratory direct shear test. This illustrates that the proposed DEM equivalent model can approximately simulate the mechanical characteristics of the conditioned sands,which provides the basis for further simulation of the interaction between the conditioned soil and the chamber pressure system of the EPB machine.

Optimal arrangement for pressure measurement points in working chamber of earth pressure balance shield

In order to exactly provide scientific basis for pressure dynamic balance control of working chamber of earth pressure balance shield (EPBS),study on optimal arrangement of pressure measurement points in working chamber was conducted. Based on mathematical description of optimal arrangement for pressure measurement points,fuzzy clustering analysis and discriminant analysis were used to divide pressure regions of nodes on bulkhead. Finally,the selection method of optimal measurement points was proposed,and by selecting d6.28 m EPBS as study object,the case study was conducted. By contrast,based on optimal arrangement scheme of pressure measurement points,through adopting weighted algorithm,the absolute error mean of equivalent pressure of working chamber is the smallest. In addition,pressure curve of optimal arrangement points presents parabola,and it can show the state of pressure distribution on bulkhead truly. It is concluded that the optimal arrangement method of pressure measurement points in working chamber is effective and feasible,and the method can provide basis for realizing high precision pressure control of EPBS.

Evaluation and prediction of earth pressure balance shield performance in complex rock strata:A case study in Dalian,China

This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.

Feasibility study of tar sands conditioning for earth pressure balance tunnelling

This paper presents the results of laboratory test on the feasibility of soil conditioning for earth pressurebalance （EPB） excavation in a tar sand, which is a natural material never studied in this respect. Thelaboratory test performed is based on a procedure and methods used in previous studies with differenttypes of soils, but for this special complex material, additional tests are also conducted to verify particularproperties of the tar sands, such as the tilt test and vane shear test usually used in cohesive materials, anda direct shear test. The laboratory test proves that the test procedure is applicable also to this type of soiland the conditioned material can be considered suitable for EPB excavations, although it is necessary touse a certain percentage of fine elements （filler） to create a material suitable to be mixed with foam. Thetest results show that the conditioned material fulfils the required standard for an EPB application.

Earth pressure balance control for EPB shield

This paper mainly deals with the critical technology of earth pressure balance (EPB) control in shield tunneling. On the assumption that the conditioned soil in the working chamber of the shield is plasticized, a theoretical principle for EPB control is proposed. Dynamic equilibrium of intake volume and discharge volume generated by thrust and discharge is modeled theoretically to simulate the earth pressure variation during excavating. The thrust system and the screw conveyor system for earth pressure control are developed based on the electro-hydraulic technique. The control models of the thrust speed regulation of the cylinders and the rotating speed adjustment of the screw conveyor are also presented. Simulation for earth pressure control is conducted with software AMESim and MATLAB/Simulink to verify the models. Experiments are carried out with intake control in clay soil and discharge control in sandy gravel section, respectively. The experimental results show that the earth pressure variations in the working chamber can be kept at the expected value with a practically acceptable precision by means of real-time tuning the thrust speed or the revolving speed of discharge system.

Deviation correction strategy for the earth pressure balance shield based on shield–soil interactions

The control system presently used in shield posture rectification is based on driver experience,which is marginally reliable.The study of the related theory is flawed.Therefore,a decision-making approach for the deviation correction trajectory and posture rectification load for an earth pressure balance(EPB)shield is proposed.A calculation model of posture rectification load of an EPB shield is developed by considering the interactions among the cutter head,shield shell,and ground.The additional position change during the shield attitude correction is highlighted.The posture rectification loads and shield behaviors results can be solved by the proposed method.The influences of the stratum distribution(i.e.,bedrock height in the upper-soft and lower-hard strata)on shield behaviors and posture rectification loads are analyzed.Results indicated that the increase of pitch angle in the upper-soft and lower-hard strata causes a sharp rise in vertical displacement.The bedrock height increases the magnitudes of the required posture rectification moments when hr/D>0.5.For a tunnel with hr/D≤0.5,the variation of hr/D has little effect on the posture rectification moments.Finally,the posture rectifying curves based on the theoretical model are compared with the target ones based on the double circular arc interpolation method.The required results can be obtained regardless of the soil–rock compound stratum distribution.The maximum rectification moment in the rock layer is almost 12.6 times that in the soil layer.Overall,this study provides a valuable reference for moment determination and the trajectory prediction of posture rectification in compound strata.

EPB盾构刀盘泥饼成因分析及评价模型构建

目前土压平衡(EPB)盾构机刀盘结泥饼的研究大都聚焦在单一因素上,缺少整体的、量化的评价标准,难以满足工程上对刀盘结泥饼的预测需求。针对以上问题,文中从地质条件、盾构选型、施工因素3个层面出发,系统总结了导致土压平衡盾构机刀盘泥饼形成的23个主要因素;将土压平衡盾构机在掘进过程中的刀盘结泥饼风险划分为4个等级:高风险、中风险、低风险和无风险。同时提出了结泥饼的风险因子量化标准,并结合层次分析法构建了土压平衡盾构的刀盘结泥饼风险评价模型;基于广州地铁14号线马创区间右线115-165环盾构隧道工程的掘进数据,计算出盾构机掘进过程中不同环的刀盘结泥饼风险程度,验证了刀盘结泥饼风险评价模型的预测性能。研究结果表明:结泥饼风险评价模型的23个影响因子中,以塑性指数、刀盘扭矩、液性指数、总推力的影响权重最大,启动扭矩的影响权重最小;结泥饼风险评价模型表现出了良好的预测性能,计算得到的结泥饼风险变化曲线与现场施工情况基本吻合;盾构掘进参数的变化能很好地反映掘进过程中泥饼的形成,其中总推力对泥饼产生最敏感,刀盘扭矩、土仓压力、推进速度和螺旋机转速的敏感度依次降低。研究成果可适用于类似工程中的土压平衡盾构机刀盘结泥饼的评价分析。

EPB盾构信息化管理系统在广州地铁的应用

针对广州地铁二号线赤岗-鹭江区间盾构隧道工程,在分析盾构法隧道施工过程以及工程特点、施工扰动引起周围土体变形的规律、土压平衡盾构各种施工参数对施工变形的影响程度、盾构隧道土体及相关构筑物的沉降监测方法的基础上,对盾构隧道工程数据进行合理的分类,开发了“盾构隧道施工多媒体监控与仿真系统”软件。建立了工程信息数据库、施工监控与施工参数自动采集、地面沉降预测、盾构施工参数控制和地表沉降三维可视化显示等功能,通过多种数据查询器对工程信息实行集中维护和查询,进行地层及相关构筑物和管线沉降的预测、报警,并根据监测数据对盾构施工参数进行控制。

二次调节技术在盾构EPB模拟系统惯性能回收中的应用

提出一种基于二次调节技术的盾构土压平衡系统,系统制动过程中调节二次元件的排量作泵工况,在螺旋输送机的惯性带动下向系统回馈能量。模拟实验表明,这种基于二次调节技术的盾构土压平衡系统能取得明显的惯性能回收效果,系统能量回收效率受二次元件的排量、系统油源压力及转速等参数的影响,在能量回收过程中实行恒转矩控制能使系统制动过程平缓,并能满足制动时间等要求。

盾构EPB模拟实验系统的建模与仿真

采用功率键合图方法,建立了盾构土压平衡模拟实验系统的数学模型,利用模拟实验系统实验数据,辨识出了模型的参数。实验证明该模型的数字仿真结果与模拟实验相吻合,表明所建立的模型可以代替模拟实验系统。利用该模型进行数字仿真,不受物理模拟实验系统的限制,可以拓宽模拟实验研究范围,为盾构土压平衡系统的动态分析和优化设计提供理论支持。

EPBS施工地下水压对气泡改良砂土渗透性影响

通过自制的压力舱模型对水压力对气泡改良砂土渗透性的影响进行了试验研究,分析了水头压力对气泡改良砂土渗透性的影响规律,并对不同砂样进行了比较,明确了砂土的级配对试验结果的影响,从而可以进一步清楚在这种富水砂层中应选用怎样的改良方案。

EPB盾构机工作面土压力和油缸推力合理优化

基于Rankine的主动和被动土压力理论,采用解析方法建立了合理确定EPB盾构机工作面压力方法,给出了EPB(Earth Pressure Blance)盾构机随埋深和土体力学参数的变化关系。根据力的平衡原理,推导了EPB盾构机推力与盾构机埋深、土体力学参数和盾构机几何尺寸的解析表达式。数值计算结果表明,所提出的推力计算方法与现场实际采用的数值基本一致。

Real-time analysis and prediction of shield cutterhead torque using optimized gated recurrent unit neural network

An accurate prediction of earth pressure balance(EPB)shield moving performance is important to ensure the safety tunnel excavation.A hybrid model is developed based on the particle swarm optimization(PSO)and gated recurrent unit(GRU)neural network.PSO is utilized to assign the optimal hyperparameters of GRU neural network.There are mainly four steps:data collection and processing,hybrid model establishment,model performance evaluation and correlation analysis.The developed model provides an alternative to tackle with time-series data of tunnel project.Apart from that,a novel framework about model application is performed to provide guidelines in practice.A tunnel project is utilized to evaluate the performance of proposed hybrid model.Results indicate that geological and construction variables are significant to the model performance.Correlation analysis shows that construction variables(main thrust and foam liquid volume)display the highest correlation with the cutterhead torque(CHT).This work provides a feasible and applicable alternative way to estimate the performance of shield tunneling.

富水砂卵石地层EPB盾构衡盾泥辅助施工关键技术研究

以长沙市某电力盾构隧道为背景,针对富水砂卵石地层中传统泥膜护壁工艺和地表沉降控制技术的不足,通过室内试验和现场实践的方法,进行了富水砂卵石地层衡盾泥辅(HDN)助带压换刀和盾构掘进地表沉降控制关键技术研究。现场实践表明:在衡盾泥辅助带压换刀施工中,注入衡盾泥后在富水砂卵石地层的开挖面形成的泥膜质量好,泥膜护壁效果非常明显,有效解决了渗水透气问题;在衡盾泥辅助盾构掘进中,衡盾泥可有效填充盾体与土体之间的开挖间隙,显著提高了同步注浆及二次注浆效果,累计地表沉降最大值仅为5.75 mm,达到了盾构推进时的沉降控制目标。

基于机器学习的EPB盾构土仓压力预测方法研究

为了避免因土压平衡盾构(EPB)土仓压力失衡造成的掌子面失稳、地层缺失和地表沉降等后果,将GA算法嵌入到PSO算法进行参数优化,结合灰色理论建立基于灰色最小二乘支持向量机的土仓压力预测模型,并以实际工程为案例进行了验证。研究结果表明:GA-PSO-GLSSVM土仓压力预测模型将总推力、刀盘扭矩、推进速度、螺旋机转速、螺旋机扭矩、注浆量6种掘进参数作为输入集,综合考虑了盾构掘进参数之间的相互影响,使预测模型更符合实际;该预测模型综合了GA算法的全局搜索能力、PSO算法的快速收敛能力和GM模型抗扰动能力,提高了复杂地层EPB土仓压力预测的精度;与其他预测模型预测结果的对比表明,GA-PSO-GLSSVM模型预测结果的均方根误差(RMSE)、平均绝对误差(MAE)、平均绝对百分比误差(MAPE)、可决系数(R^(2))明显优于其他模型,预测结果拟合优度和精确度更高,对砂卵石这类复杂地层中EPB盾构土仓压力的预测具有显著的适用性。研究结果可为砂卵石地层EPB盾构施工掘进参数控制提供参考。

EPB盾构机刀盘工况分析与结构优化

在确定不同工况条件下EPB(土压平衡式)盾构机刀盘载荷边界条件的基础上,对刀盘的强度和刚度进行有限元模拟分析,提出采用加强筋的方式增强刀盘面板强度的方法,最终结果表明改进后的刀盘变形均匀,强度和刚度均有大幅度提升。

基于恒压网络的双圆盾构EPB模拟实验系统建模及仿真

采用功率键合图法建立基于恒压网络的单圆盾构土压平衡模拟实验系统仿真模型,并验证模型的有效性。在此仿真模型基础上,利用仿真模型不受物理条件限制的优点,建立了基于恒压网络的双圆盾构土压平衡模拟实验系统仿真模型,并进行了仿真研究。仿真结果表明,模型可基本实现双圆盾构土压平衡模拟实验系统的工况模拟,对建立基于恒压网络的双圆盾构土压平衡模拟实验系统有借鉴作用。

复杂地层EPB/TBM双模式盾构掘进性能分析

为探究EPB/TBM双模式盾构在土层、土岩结合地层、长距离硬岩等复杂地层中掘进性能的优势及不同模式下各种地层中掘进参数变化、刀具消耗的规律,从怀福区间左线掘进各项施工参数分析入手,收集自盾构始发至模式转换到出洞完整施工周期的施工参数,对比双模式盾构在相同模式下不同地层、不同模式下相同地层的参数变化、掘进工效的变化情况,分析每个影响施工效率的参数因素。得到:1)在EPB施工模式下,土压力和刀盘转速对掘进参数影响明显,在软土地层中,要保证地面变形在设计范围内,应尽可能降低土压力;在岩石地层中,应尽量减少积渣高度,提高刀盘转速,以提高推进速度,从而得到更高的施工效率。2)在TBM施工模式下,掘进参数主要受岩体节理发育程度影响,应及时根据岩体的节理发育调整转速、贯入度等参数,以此提高TBM模式下的施工效率。通过分析在硬岩掘进过程中对应不同地质情况、不同模式下刀具消耗的位置及消耗的原因,得到在全断面硬岩掘进条件下降低刀具正常损耗的主要因素在于降低土舱内存渣量对滚刀的二次磨损的施工建议。

EPB隧道掘进对软岩地层地表影响分析

以城际快速轨道南京南站至禄口机场站1号盾构井工程为依托,分析土压平衡盾构模式掘进对软岩地层地表影响,减小城市环境下土压平衡盾构模式掘进对下穿建筑物影响,确保隧道施工安全。为此,运用FLAC显式有限差分软件进行建模,通过对土仓压力、同步注浆效果和出碴量等影响因素的分析,研究了土压平衡盾构模式掘进对软岩地层地表沉降的影响,确定了合理的掘进控制参数。

考虑推进过程的土压平衡盾构渗流场解析解及喷涌判别

考虑推进过程中盾构正面附加推力产生的超孔隙水压力,用解析的方法分析了盾构喷涌问题。将土舱渗流场划分成两个区域,利用叠加原理和分离变量法得到土舱水头显式级数解,将螺旋输送机内流场视为一维渗流,通过土舱与螺旋输送机交界面的连续条件确定盾构渗流场解析解。通过数值模拟结果验证了解的正确性,并进行了参数分析。参数分析表明:正常掘进状态下的盾构推力波动频率与渣土固结系数比值近似为0.1~10 m^(-2),可对应于渗透系数10^(-3)~10^(-5)cm/s,当比值大于20 m^(-2),可以忽略超孔隙水压力的影响,比值小于0.01 m^(-2)时,水压力分布近似稳态渗流状态,但比值在1 m^(-2)附近时,超孔隙水压力将存在显著的影响。结合已有的喷涌研究,给出了典型盾构在不同推力波动频率与土体固结系数比值下的临界渗透系数。通过对盾构喷涌实例进行对比,证明了解析解的喷涌判别是有效的。