围压对TBM滚刀破岩影响规律的线性切割试验研究

 随着TBM技术在深埋隧道工程领域的应用及发展,TBM开挖过程中由高埋深或各向异性引起的岩石应力问题越来越受到人们的重视。应用北京工业大学自行研制的大型机械破岩试验平台,对4组双向等围压水平下(0,5,10和15 MPa)的大尺寸(1.0 m×1.0 m×0.6 m)北山花岗岩岩样进行线性切割试验,研究不同围压条件下滚刀破岩时作用力的曲线特征,分析围压对滚刀法向力、滚动力、岩体特征掘进指数、破岩岩片厚度和破岩比能的影响效应,并探讨围压对TBM现场掘进速率的影响。研究结果可为不同地应力条件下TBM开挖时刀盘动力参数设计与施工运行参数优化提供参考。     

基于岩碴粒径分布规律的TBM破岩效率分析

岩碴的形状、大小及其粒径分布规律是综合反映TBM破岩效率的重要指标,也是TBM掘进参数与岩石性质的重要联系。根据盘形滚刀破岩机制,对TBM掘进岩碴进行了现场量测和筛分试验,获得了TBM岩碴尺寸特征和粒径分布规律。在此基础上,对实测岩碴尺寸和粒径分布数据进行了统计分析和理论分布函数拟合。分析了粗糙度指数与岩石强度、岩石耐磨性的关系,探讨了不同围岩等级下粗糙度指数随掘进推力的变化规律。研究结果表明:①片状岩碴的长轴与短轴之比约为1.5,而长轴与厚度之比则差别较大,其长轴、短轴和厚度均服从正态分布;②不同岩性条件下岩碴粒径分布均符合Rosin–Rammler函数分布;③岩碴粗糙度指数越大,TBM破岩效率越高;硬岩条件下岩碴粗糙度指数随单轴饱和抗压强度增大而减小,而中硬—软岩条件下则相反;④无论是软岩还是硬岩,岩碴粗糙度指数随岩石耐磨性增大而减小,岩石耐磨性越强,TBM破岩效率越低;⑤TBM破岩效率与围岩等级密切相关,可根据现场实测岩碴粒径分布规律,确定Ⅱ级和Ⅲ级围岩条件下TBM破岩效率最佳时的掘进推力区间。     

围压对 TBM 滚刀破岩影响机制研究

穿越高大山体的隧道TBM施工不可避免地会遇到高地应力问题,研究地应力对TBM滚刀破岩机制和掘进效率的影响具有重大的工程价值和科学意义。通过理论分析和UDEC数值模拟技术对围压作用下滚刀破岩模式进行研究,发现围压对滚刀破岩过程影响比较复杂:围压对粉碎区深度和裂纹扩展区内滚刀作用方向的裂纹扩展起到抑制作用;而对围压作用方向的裂纹扩展有促进作用,表现为边裂纹的扩展范围会更大,扩展路径会更加平直,发展更加迅速,滚刀间岩片的形成更加容易。TBM现场掘进试验表明,地应力越高,围压作用越明显,TBM破岩更加容易,掘进效率会更高。从TBM滚刀作用下岩片形成的难易程度角度考虑,理论分析、数值模拟和TBM现场掘进试验都表明围压作用促进TBM滚刀破岩。     

不同控制模式对TBM滚刀破岩性能影响的室内试验研究

为研究不同控制模式对隧道掘进机（TBM）滚刀破岩力的影响,采用盾构与掘进国家重点实验室的机械破岩平台,分贯入度控制模式和推力模式对水泥砂浆试件进行室内全尺寸旋转切削试验。分析不同控制模式下法向力、滚动力、切削系数、比能和岩体可掘进指数的变化规律,结果显示恒推力模式的岩石切削效率比恒贯入度控制模式高。     

不同层厚层状岩体对TBM开挖的影响

 TBM的开挖效果在很大程度上受到节理间距的影响,TBM掘进速度随节理间距变小而增大,但节理间距过小,会造成掌子面岩体不稳,不利于TBM开挖。锦屏II级水电站引水隧洞洞段主要以层状大理岩为主,沿洞轴线方向大理岩层层厚变化较大,从几厘米到几米不等,层面是岩体中主要的不连续面,且层面与隧道轴线大角度相交。TBM的破岩过程主要受到高地应力条件和岩体层厚的影响。从TBM破岩机制角度,分析在高地应力条件下TBM在薄层面、中薄层面和厚层面大理岩层状岩体中的开挖表现,研究岩层厚度对TBM开挖的影响。     

复合岩体的TBM破岩机理数值模拟

为了指导TBM刀盘刀具的研制和不同地质条件下刀盘刀具的选型,TBM破岩机理的研究成为核心。在TBM滚刀的作用下,岩体中裂纹的生成、扩展和连接规律是深刻理解TBM破岩机理的前提,因此,TBM滚刀破岩机理的研究具有重要的工程应用价值。目前,TBM滚刀破岩机理的研究主要集中在单一岩体中,但在TBM施工过程中会遇到各种复杂的地质条件。笔者采用离散元方法,研究了复合岩体的破岩机理,复合岩体中岩片的形成不同于单一岩体,其裂纹的最终连接是由起裂于复合岩体交界面上的微裂纹的扩展,将两滚刀之间的赫兹裂纹连接,最终形成岩片。因此,在一定情况下复合岩体更有利于TBM隧道施工。     

围压对TBM滚刀破岩影响的数值模拟研究

采用一种新的无网格数值计算方法—广义粒子动力学法(GPD),研究了水平方向围压为0,5,10,15,20 MPa条件下,全断面隧道掘进机(TBM)滚刀的破岩过程及破岩模式,分析了围压对岩体可掘性的影响。得到:(1)围压的存在抑制中央裂纹的扩展;(2)随着围压的增加,赫兹裂纹的扩展方向发生偏转,与水平面的夹角变小;(3)相同贯入度下,随着围压的增加,滚刀法向力及其掘进指数均增加。利用GPD法分析了锦屏二级水电站隧道施工中,含节理的岩层中高地应力对TBM滚刀破岩的影响,成功模拟出高地应力下节理岩体的板裂化现象,得到高地应力能够使岩体产生板裂化促进滚刀破岩。     

大坡度斜井TBM溜渣试验研究及TBM优化设计

对山东文登抽蓄电站TBM渣片粒径、含水率、溜渣临界倾角等因素进行分析,对山东文登抽蓄电站TBM渣片粒径重新级配,开展利于出渣的渣片最优级配研究.基于试验结果,对斜井TBM刀盘、刀具布置、喷水及掘进参数进行优化,使斜井TBM出渣的粒径分布与含水率满足斜井自溜出渣的要求.研究结果对斜井TBM优化设计及掘进管理具有参考意义.     

节理间距对滚刀破岩影响的线性破岩试验研究

掘进机(TBM)开挖过程中受到各种地质因素的影响,其中节理间距是影响TBM滚刀破岩的一个重要因素。设计节理间距为100mm和400mm两组试验方案。试样为甘肃北山花岗岩,应用北京工业大学自行研制的大型机械破岩实验平台,选用17英寸(432mm)的常截面盘形滚刀进行线性切割破岩试验。试验过程中记录滚刀三向力、滚刀下岩样裂纹扩展并收集了岩片。从三向力、裂纹的扩展模式和岩片等角度分析节理间距对滚刀破岩的影响。结果表明:节理间距100mm的岩体切入所需要的推力小于完整岩石的推力,节理间距400mm的岩体破岩过程中推力有一突变的过程。节理间距100mm岩体滚刀作用下存在两种破坏模式,节理间距400mm的岩体破岩过程则包括了正常破岩和节理面影响破岩两个过程,并且节理对竖向主裂纹向节理面扩展有加剧的作用。节理面下方岩石较完整,节理面阻碍裂纹朝节理面下方岩石传播。     

花岗岩地层中双护盾TBM掘进参数变化规律分析

TBM在掘进过程中,掘进参数在不同的围岩条件中需要不断地进行调整,合理选择掘进参数以满足施工安全与质量的要求。文章以青岛地铁4号线鞍山路站~错埠岭站区间双护盾TBM施工为背景,收集TBM总推力、刀盘扭矩、掘进速度、刀盘转速等掘进参数,并结合不同里程段花岗岩地层的单轴饱和抗压强度、完整性系数、抗拉强度、弹性模量、泊松比等岩体指标进行统计分析。通过掘进参数统计分析、各参数间单因素相关性分析、总推力与饱和单轴抗压强度和完整性系数间的回归拟合分析,得出TBM掘进参数变化区间与规律,为相似工程TBM掘进参数的预测提供参考。     

In situ TBM penetration tests and rock mass boreability analysis in hard rock tunnels

Boreability is popularly adopted to express the ease or difficulty with which a rock mass can be penetrated by a tunnel boring machine. Because the boreability is related to the rock mass properties, TBM specifications and TBM operation parameters, an accurately definable quantity has not been obtained so far. In order to analyze and compare rock mass boreability, a series of TBM shield friction tests were conducted in a TBM tunneling site. Two sets of TBM penetration tests were performed in different rock mass conditions during tunneling in rock. In each step of the penetration test, the rock muck was collected to perform the muck sieve analyses and the shape of large chips was surveyed in order to analyze the TBM chipping efficiency under different cutter thrusts. The results showed that a critical point exists in the penetration curves. The penetration per revolution increases rapidly with increasing thrust per cutter when it is higher than the critical value. The muck sieve analysis results verified that with increasing thrust force, the muck size increases and the rock breakage efficiency also increases. When the thrust is greater than the critical value, the muck becomes well-graded. The muck shape analysis results also showed with the increase of the thrust, the chip shape changes from flat to elongated and flat. The boreability index at the critical point of penetration of 1 mm/rev. defined as the specific rock mass boreability index is proposed to evaluate rock mass boreability.     

Analysis and prediction of TBM performance in blocky rock conditions at the Lötschberg Base Tunnel

This paper focuses on the analysis of the TBM performance recorded during the excavation of the Lötschberg Base Tunnel. The southern part of the tunnel was excavated by two gripper TBMs, partly through blocky rock masses at great depth. The jointed nature of the blocky rock mass posed serious problems concerning the stability of the excavation face. A detailed analysis has been carried out to obtain a relationship between the rock mass conditions and the TBM performance, using the Field Penetration Index (FPI). In blocky rock conditions, the FPI is defined as the ratio between the applied thrust force and the actual penetration rate. A database of the TBM parameters and the geological/geotechnical conditions for 160 sections along the tunnel has been established. The analysis reveals a relationship between the FPI and two rock mass parameters: the volumetric joint count (J_v) and the intact rock uniaxial compressive strength (UCS). Through a multivariate regression analysis, a prediction model for FPI in blocky rock conditions (FPI_blocky) is then introduced. Finally, other TBM performance parameters such as the penetration rate, the net advance rate and the total advance rate are evaluated using FPI_blocky.     

Correlation of tunnel convergence with TBM operational parameters and chip size in the Ghomroud tunnel, Iran

Evaluating the impact of rock mass properties on a tunneling operation is crucial, especially when using a tunnel boring machine (TBM). It is an integral part of machine selection and performance prediction in the design and bidding stage. Monitoring and analysis of ground conditions during the construction is also essential to allow the operator to take precautionary measures in adverse geological conditions. This involves adjusting TBM operational parameters such as machine thrust and penetration to avoid potential problems caused by face collapse or excessive convergence and subsequent machine seizure that can cause long delays. Tunnel wall convergence is a function of rock mass characteristics, in situ stresses, size of excavation, and rate of penetration (ROP). It is one of the main factors in determining the use of shielded machines in deep rock tunnel projects. The case study of the Ghomroud water conveyance tunnel project, under construction by a double shield TBM, is used to examine the effect of rock mass parameters on tunnel convergence and hence on the need for over excavation and shield lubrication to avoid problems such as shield seizure. Results of a preliminary analysis of field observations show that the amount of the tunnel convergence can have a direct relationship with the percentage of powder and large rock fragments in the muck. In addition, tunnel convergence has shown a strong relationship with the TBM thrust/torque and rate of penetration (ROP). These relationships have been examined and the results of the analysis as well as the resulting formulas will be explained in this paper.     

Study on rock mass boreability by TBM penetration test under different in situ stress conditions

Rock mass boreability is a comprehensive parameter reflecting the interaction between rock mass and a tunnel boring machine (TBM). Many factors including rock mass conditions, TBM specifications and operation parameters influence rock mass boreability. In situ stress, as one of the important properties of rock mass conditions, has not been studied specifically for rock mass boreability in TBM tunneling. In this study, three sets of TBM penetration tests are conducted with different in situ stress conditions in three TBM tunnels of the Jinping II Hydropower Station. The correlation between TBM operation parameters collected during the tests and the rock mass boreability index is analyzed to reveal the influence of in situ stress on rock mass boreability and TBM excavation process. The muck produced by each test step is collected and analyzed by the muck sieve test. The results show that in situ stress not only influences the rock mass boreability but also the rock fragmentation process under TBM cutters. If the in situ stress is high enough to cause the stress-induced failure at the tunnel face, it facilitates rock fragmentation by TBM cutters and the corresponding rock boreability index decreases. Otherwise, the in situ stress restrains rock fragmentation by TBM cutters and the rock mass boreablity index increases. Through comparison of the boreability index predicted by the Rock Mass Characteristics (RMC) prediction model with the boreability index calculated from the penetration test results, the influence degree of different in situ stresses for rock mass boreability is obtained.     

复杂岩石地层隧道掘进机操作特性分析

为提高掘进效率,改进掘进机与地层的匹配性设计,对掘进机的操作特性进行研究。基于重庆越江隧道盾构掘进试验,分析复杂岩石地层盾构刀盘扭矩、刀盘推力及转速的参数选用原则,在此基础上,分析主掘进参数与切深的关系。随后,对不同地层条件下刀盘扭矩与推力之间的匹配性进行分析,绘制了刀盘扭矩与推力之间的操作特性曲线,并用于分析和制定不同地层条件下的主掘进参数匹配方案。对于较软的泥岩,刀盘扭矩先达到最大值,而推力却不能发挥其最大能力;岩石强度增高,所需推力增加,在发挥扭矩能力的前提下,推力也能发挥其功能,从而使二者达到最佳操作关系;若岩石强度过高,推力保持在最大值,但切深很浅,滚刀旋转阻力减小,刀盘扭矩很难发挥最大能力。因此,应视地层软硬,根据刀盘推力与扭矩的操作特性对刀盘的主掘进参数进行合理设计,并在掘进过程中实时调整其匹配关系。     

高地应力区双护盾TBM隧道围岩性态即时判示分析

青藏高原及其东缘高山区的交通建设和能源开发,需要修建众多的深埋长大隧道,采用TBM掘进具有显著优势.依托西藏雅鲁藏布大峡谷DXL隧道双护盾TBM掘进施工,就隧址区工程地质环境、基于尾渣的围岩特征信息的即时获取方法以及围岩性态判别等进行了研究.结果表明:(1)高地应力环境下,隧址区裂隙性硬质围岩微细观破裂,造成宏观大变形...     

Hard rock tunnel boring machine penetration test as an indicator of chipping process efficiency

The transition from grinding to chipping can be observed in tunnel boring machine(TBM) penetration test data by plotting the penetration rate(distance/revolution) against the net cutter thrust(force per cutter) over the full range of penetration rates in the test.Correlating penetration test data to the geological and geomechanical characteristics of rock masses through which a penetration test is conducted provides the ability to reveal the efficiency of the chipping process in response to changing geological conditions.Penetration test data can also be used to identify stress-induced tunnel face instability.This research shows that the strength of the rock is an important parameter for controlling how much net cutter thrust is required to transition from grinding to chipping.It also shows that the geological characteristics of a rock will determine how efficient chipping occurs once it has begun.In particular,geological characteristics that lead to efficient fracture propagation,such as fabric and mica contents,will lead to efficient chipping.These findings will enable a better correlation between TBM performance and geological conditions for use in TBM design,as a basis for contractual payments where penetration rate dominates the excavation cycle and in further academic investigations into the TBM excavation process.     

Predicting penetration rate of hard rock tunnel boring machine using fuzzy logic

Predicting the penetration rate of a tunnel boring machine (TBM) plays an important role in the economic and time planning of tunneling projects. In the past years, various empirical methods have been developed for the prediction of TBM penetration rates using traditional statistical analysis techniques. Soft computing techniques are now being used as an alternative statistical tool. In this study, a fuzzy logic model was developed to predict the penetration rate based on collected data from one hard rock TBM tunnel (the Queens Water Tunnel # 3, Stage 2) in New York City, USA. The model predicts the penetration rate of the TBM using rock properties such as uniaxial compressive strength, rock brittleness, distance between planes of weakness and the orientation of discontinuities in the rock mass. The results indicated that the fuzzy model can be used as a reliable predictor of TBM penetration rate for the studied tunneling project. The determination coefficient (R ²), the variance account for and the root mean square error indices of the proposed fuzzy model are 0.8930, 89.06 and 0.13, respectively.     

掘进机刀盘滚刀间距对北山花岗岩破岩效率的影响实验研究

掘进机(TBM)开挖隧道过程中,其刀盘上滚刀间距设计的合适与否关系着破岩效率的高低。由于岩石非均匀、非连续、各项异性的特性,使用数值模拟方法研究滚刀破岩过程存在局限性。现场掘进实验主要是针对特定的掘进机做出机械运行参数优化,无法研究不同刀间距对破岩的影响。全尺寸滚刀破岩实验可以人为调整刀间距,且实验中采用大体积岩石可以避免尺寸效应的影响,因此受到了广泛的关注。采用北京工业大学自制的机械破岩试验平台,安装17英寸(432 mm)盘形滚刀,选取尺寸为1000 mm×1000 mm×600 mm的北山完整花岗岩试样,进行了5组刀间距的线性切割试验。实验中采集滚刀三向力,分层收集岩片且对其进行称重。对不同刀间距作用下的平均法向力、平均滚动力和比能进行了分析研究。当贯入度较小时,刀间距对平均法向力和平均滚动力的影响都不明显,随着贯入度的增加,刀间距对平均法向力和平均滚动力的影响增加。对于所有的刀间距而言,增加贯入度会产生更多的岩片,但并不一定会提高破岩效率,对于北山花岗岩而言,当刀间距与贯入度的比值为30左右时,比能值最低,此时破岩效率最高。     

复杂岩石地层盾构掘进效能影响因素分析

基于现场掘进试验和岩石点荷载强度试验,对泥岩、砂岩交互地层条件下泥水盾构的掘进效能及其影响因素进行研究.利用现场采集的数据,运用回归分析的方法,主要分析盾构掘进效能与岩石强度、刀盘推力及刀盘扭矩的关系.研究成果表明,岩石强度越高,刀盘每转切深和掘进速率就越低,二者呈幂函数曲线关系;随着刀盘推力的增大,切深呈幂函数关系增加;而随着刀盘切深的增加,刀盘扭矩则呈线性增加.对比两种地层的掘进特性,相对而言,泥岩地层掘进效能较高,但需要较大的扭矩,而在砂岩地层掘进需要较大的推力才能获得理想的掘进效能.