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。     

基于耦合FDM-DEM方法的TBM滚刀最优化研究

为确定TBM盘型滚刀的最优布置,结合有限差分法(FDM)和离散元法(DEM)的优点,采用FDM-DEM耦合的数值模拟方法,对不同刀间距和贯入度条件下TBM双滚刀破岩过程进行三维动态仿真模拟,分析研究了不同滚刀配置对岩石破碎效果的影响。为了验证所提出方法的可行性和准确性,利用线性切割机(LCM)对科罗拉多红色花岗岩进行了切割试验,通过对比分析线性切割试验数据,验证了所提出方法的可行性。数值模拟结果表明：对于科罗拉多红色花岗,滚刀法向力和切向力会随着刀间距和贯入度比值的增加先减少后增大,当刀间距和贯入度的比值为20左右,滚刀法向力和切向力最小。线性切割试验和数值模拟结果均表明,当间距和贯入度的比值在17～20左右,岩石切割的比能量最低,此时TBM切割效率最高。文章提出方法的方法可以为TBM滚刀刀头配置提供重要依据。     

Study on the influence of joint spacing on rock fragmentation under TBM cutter by linear cutting test

Joint spacing is one of the most important geological factors influencing rock fragmentation by TBM cutters and TBM performance. In order to study the influence of joint spacing, full-scale linear cutting tests have been conducted for the Beishan granite samples with different joint spacing (i.e. one intact sample, two jointed samples with joint spacing of 100 mm and 400 mm). For different joint spacing, the influence of penetration depth on rock fragmentation was also explored by varying the penetration depth with an interval of 0.5 mm. During the test process, the three directional forces acting on the TBM cutter were recorded, and the rock chips formed by each cutting pass were weighed, respectively. By analysing the cutting force, crack initiation/propagation and rock chips, the influences of joint spacing on rock fragmentation process by TBM cutter were investigated. The test results showed that the increase of penetration depth cannot improve the TBM breakage efficiency after reaching a certain value for the intact rock sample, and the normal force for intruding the intact rock is larger than that for intruding the rock jointed samples. It is also found that the sample part below the joint plane is intact, thus joint can restrain the crack propagating cross the joint plane and facilitates the chips formation on the cutting surface. For the rock sample with joint spacing of 100 mm, two rock fragmentation modes were found during the cutting process. One mode is that the cracks initiate from the crushed zone under TBM cutter, and the cracks propagate to the joint plane, consequently form large rock chips. The other one is that the cracks initiate from the joint plane and then propagate to the rock cutting surface, and the cracks initiate before the formation of the crushed zone under the cutter. For the rock sample with joint spacing of 400 mm, there are two rock fragmentation stages, i.e., the normal rock fragmentation stage and the joint-controlled rock fragmentation stage. There is a transitional process between these two stages, and also the median crack can be promoted to propagate vertically to joint plane due to the joint existence. This study can provide useful guidance for operation optimization and performance prediction for TBM operating in jointed rock masses.     

Study on the influence of confining stress on TBM performance in granite rock by linear cutting test

Rock stress problems induced by overburden or anisotropic stresses are significant to the TBM tunneling. In this paper, the effect of different confining stressed conditions on TBM performance are investigated by using full-scale cutting tests with large intact granite specimens (1000 mm × 1000 mm × 600 mm). In these tests, the effects of confining stresses on the normal force, rolling force, the cutting coefficient and specific energy are analyzed. It is found that the confining stress has significant impact on the normal force and rolling force. Specifically, for the same cutting spacing and penetration depth, the normal force increases with increasing confining stress due to enhancement of the rock resistance strength; meanwhile the rolling force decreases gradually with increasing confining stress. The stress deviation between two confining directions affects the optimum penetration that corresponds to small specific energy. The results provide better understanding of the effect of confining stress on the TBM performance and also recommend some guidelines for TBM tunneling under stressed geological condition.     

Prediction of thrust and torque requirements of TBMs with fuzzy logic models

For successful tunnel excavations, selection of proper tunnel boring machine (TBM), optimization of design parameters and prediction of their performance are critical. Normal and rolling forces of disc cutters are used for determination of thrust, torque and power requirement of TBMs as well as prediction of their performance. Much research has been conducted to predict these parameters of disc cutters using analytical, empirical and numerical approaches. In recent years alternative methods, such as fuzzy logic, have been extensively used to deal with subjects having ambiguities and uncertainties. A model was established to predict normal forces of constant cross section (CCS) disc cutters in the rock cutting process by using fuzzy logic method. The other model which predicts specific energy requirement of disc cutter can also be used for predicting the rolling forces of these cutters. These models are based on experience and verified the database which consists of linear cutting test results generated at the Earth Mechanics Institute of the Colorado School of Mines. The models predict forces of disc cutters using uniaxial compressive and tensile strength of rocks, disc diameter and tip width, penetration and spacing of cuts.     

Correlation of rock cutting tests with field performance of a TBM in a highly fractured rock formation: A case study in Kozyatagi-Kadikoy metro tunnel,Turkey

This paper presents and discusses detailed field and laboratory studies concerning boreability prediction of tunnel boring machines (TBMs) used in Kozyatagi-Kadikoy metro tunnels in Istanbul in a highly fractured rock formation. The determination of some design parameters and performance prediction of a tunnel boring machine (TBM) are carried out using full-scale rock cutting test. The intact rock samples having minimum sizes of 1.0 × 0.7 × 0.7 m are obtained from shale and limestone (Kartal Formation) along the tunnel line. The rock samples are subjected to full-scale laboratory rock cutting tests with different depth of cut and cutter spacing values using a constant cross section (CCS) disc cutter of 330 mm in diameter. Cutter forces, i.e., thrust force, rolling force and specific energy values are recorded for each cut. The results of the tests are first used to calculate TBM design and performance parameters such as torque and thrust requirements and cutting rates. In the second part of the research, the field performance of the TBM is recorded with the aid of data acquisition system installed within TBM and the predicted performance and design values obtained from full-scale rock cutting tests are compared with the field values. It is observed that fractured characteristics of the rock formation affect tremendously TBM performance and predicted values differ from the field data in some extend. It is believed that the results will serve as a guide for efficient selection and use of TBMs.     

TBM滚刀破岩动态特性与最优刀间距研究

在对实际工况合理简化的基础上,从岩土细观角度出发,采用颗粒离散元法建立滚刀侵入岩体的二维模拟模型,研究双滚刀作用下岩体的动态响应机制,找出滚刀侵入过程中岩体裂纹、贯入度以及切削力三者的关系。在此基础上,通过数值模拟对常见切深下滚刀最优刀间距问题进行分析,得到不同切深下比能耗与刀间距的规律,并通过试验对双滚刀破岩过程中岩体动态特性以及最优刀间距问题进行验证,最后以工程实例验证研究结论。研究表明：仿真过程中,切削力随贯入度的变化与岩体的跃进破碎特性相一致,岩体破坏服从格里菲斯理论;较小切深下岩体为剪切破坏,较大切深下岩体发生拉应力破坏;切深为10 mm时比能耗有明显拐点,此时刀间距为100 mm;切深为6 mm时,60 mm刀间距下比能耗最小;切深小于2 mm时,实际工况下岩体不能产生贯穿裂纹。     

Dominant rock properties affecting the performance of conical picks and the comparison of some experimental and theoretical results

Conical picks are the essential cutting tools used especially on roadheaders, continuous miners and shearers and their cutting performance affects directly the efficiency and the cost of rock/mineral excavation. In this study, in order to better understand the effects of dominant rock properties on cutter performance, 22 different rock specimens having compressive strength values varying from 10 to 170 MPa are first subjected to a wide range of mechanical tests. Then, laboratory full-scale linear cutting tests with different depth of cut and cutter spacing values are realized on large blocks of rock specimens using one type of conical pick. Specific energy, cutting and normal force values for relieved and unrelieved cutting modes are recorded using a triaxial force dynamometer with capacity of 50 tonnes and a data acquisition system. Cutter force and specific energy values are correlated with rock properties and theoretical force and specific energy values obtained from widely used theoretical approaches.The results indicate that uniaxial compressive strength among the rock properties investigated is best correlated with the measured cutter performance values, which is in good agreement with previous studies. However, it is also emphasized in this study that Brazilian tensile strength, Schmidt hammer rebound values, static and dynamic elasticity modulus are also dominant rock properties affecting cutter performance.Theoretical specific energy defined by different researchers has a meaningful relationship with the experimental specific energy, which is an essential parameter for predicting the instantaneous cutting rates of mechanical excavation systems. It is also demonstrated that the experimental cutter forces obtained for 5 mm depth of cut are in good agreement with theoretical force values, if the friction angle between rock and cutting tool is included in the theoretical formulation. It is emphasized that, to some extend, laboratory tests can help to minimize high cost of a trial–error approach in the field.     

An experimental research on the rock cutting process of the gage cutters for rock tunnel boring machine (TBM)

This paper proposed an experimental method to investigate the rock cutting process of TBM gage cutters based on the full-scale rotary cutting machine (RCM). The key point of this method is to reconstruct the RCM by inserting three wedges with angles of 10°, 20° and 30° respectively into the space between the cutter base and cutter box. As a result, the rock cutting process of gage cutters with tilt angles of 10°, 20° and 30° can be proceed. Using this method, rock cutting experiments were conducted with penetrations of 2 mm, 4 mm, 6 mm and 8 mm respectively. The testing results were analysed on the rock cutting force, rock debris dimension, specific energy and cutting surface profile, and it was found that: (1) the cutting forces and specific energy of the gage cutter were lower than those of the normal cutter respectively; and (2) the depth of the rock broken zone was smaller than the cutting depth. The testing results can also be used to validate corresponding numerical models and design the layout of gage cutters.     

The use of water jets to assist free-rolling cutters in the excavation of hard rock

Earlier work has shown that the use of water jets at moderate pressure enhances mechanical cutting in hard rock. To assess the potential of this technique for use in conjunction with free-rolling cutters, a series of laboratory tests was conducted with disc and button cutters to determine the effect of variations in the jet and cutting parameters on the cutter performance. In these tests, it was found that the use of water jets at pressure in the range of 5–40 MPa can reduce the forces on a free-rolling cutter by 40 per cent, which represents a significant improvement in cutting performance. The reduction in thrust force was found to be dependent on jet pressure: the greater the pressure, the greater the reduction. The reduction in rolling force was independent of jet pressure over the range investigated. The results indicate that no additional improvements in cutting performance of any significance are to be gained by an increase in jet pressure above 40 MPa. The most effective jet configuration for the reduction of cutter forces was found to be four coherent water jets, two laterally disposed on each side of the cutter and directed at the arc of contact between the cutting edge and the rock.     

Disc cutter wear prediction for a hard rock TBM cutterhead based on energy analysis

Disc cutter wear is a crucial problem that influences the working efficiency and security of hard rock tunnel boring machines (TBMs). This wear results from friction energy accumulation and conversion. In this study, the process of hard rock TBM disc cutter wear is identified and analyzed by quantifying the collective energy change. This study starts with an analysis of the friction process between the disc cutter and hard rock. The relationship between the rolling force work and thrust force work of the disc cutter is examined. As a result, the disc cutter energy equation is determined, and the meaning of the upper and lower bounds of this equation are discussed. Based on the above results, the hard rock TBM cutterhead energy equation is then deduced. A method to identify the friction work is developed. According to the energy wear theory, the cutter wear law on hard rock for a TBM cutterhead is revealed, and a method for predicting disc cutter wear for a hard rock TBM cutterhead is advanced. Furthermore, the validity of this prediction method is confirmed by utilizing data from project cases.     

Analysis on the damage behavior of mixed ground during TBM cutting process

Accurate prediction of rock cutting forces of disc cutters is especially significant for the design and construction of tunnel boring machine (TBM). Through the analysis of motion trajectory of TBM disc cutters, a three-dimensional model of rock breaking process of disc cutters is established. In terms of the rock strain which is resulted from the interaction between disc cutters and rock during the process of rock breaking, a three-dimensional cutting forces model is proposed with disc cutters set at certain parameters and in certain sizes. Subsequently, the equation of contacting forces between rock and disc cutter is derived. Moreover, a new method has been presented for the study of the rock breaking theory of the disc cutter and it also provides guidance for the design and application of TBM in tunnel excavation. The three-dimensional model for the rock breaking mechanism is used for predicting the cutting force for the situation of mixed ground.The damage field and the rock failure zone induced by disc cutter for mixed ground are also discussed in this study. In detail, the rock damage zones are divided into two parts, one is the left damage field which located in the outside of disc cutter. The other is the right damage field which located in the outside of disc cutter. The influence of the rock ground dip on the rock failure zone was also studied by parameter analysis.     

A fuzzy logic model to predict specific energy requirement for TBM performance prediction

Prediction of tunnel boring machine performance is a critical key for successful tunnel excavations. Specific energy requirement of disc cutters, which is defined as the amount of energy required to excavate a unit volume of rock, is one of the important parameters used for performance prediction of these machines. Much research has been conducted to predict cutting parameters of disc cutters using analytical, empirical and numerical approaches. In recent years alternative methods, such as fuzzy logic, have been extensively used to deal with subjects having ambiguities and uncertainties. In this study, a model was established to predict specific energy requirement of constant cross-section disc cutters in the rock cutting process by using fuzzy logic method. This model is based on experience and the database which consists of linear cutting test results that were generated over for many years at the Earth Mechanics Institute of the Colorado School of Mines. The model predicts specific energy requirements of disc cutters using uniaxial compressive and tensile strength of rocks, disc diameter and tip width, penetration and spacing of cuts.     

Evaluation of cutting efficiency during TBM disc cutter excavation within a Korean granitic rock using linear-cutting-machine testing and photogrammetric measurement

In TBM excavation, estimation of cutting performance is of great importance in design stage as well as during construction. The performance is highly dependent on the geological conditions, i.e. characteristics of rock and discontinuities, and operational conditions, i.e. selection of cutter, cutting forces, cutter spacing, etc. For performance estimation, full scale test is most reliable and accurate since it takes full advantage of using real cutter and real size specimen. Linear cutting machine (LCM) is usually used for a full size test to evaluate the cutting performance. This paper presents the results of LCM tests carried out under various cutting conditions to assess the cutting performance of a TBM disc cutter for granitic rock in Korea. In LCM test, the excavated rock volume was determined by ShapeMetrix3D photogrammetric measurement system. This system was employed to ensure the accurate determination of cutting volume and subsequently calculated specific energy (SE). The optimum cutting condition for the Korean granitic rock was obtained at the minimum value of SE. In addition, three-dimensional numerical analysis was performed to simulate the rock cutting behavior in the LCM test. The results of the numerical simulation were closely comparable with the results of the LCM test. This study presents the cutting performance of a disc cutter by LCM test for a Korean granitic rock and demonstrates the applicability of numerical analysis as an alternative for the prediction of the cutting performance.     

岩石隧道掘进机的施工预测模型

分析了岩石隧道掘进机的破岩机理,介绍了自上世纪70年代以来发展的一系列施工预测模型,包括单因素预测模型、综合预测模型(CSM模型和NTNU模型)、岩体分类预测模型(QTBM模型)、概率模型、模糊神经网络模型。单因素预测模型中包括的主要岩石材料参数有岩石单轴抗压强度、抗拉强度及岩石的总硬度;CSM模型主要是基于线性切割试验机岩石试验数据,其初始预测模型中包括岩石单轴抗压强度及抗拉强度;NTNU模型是一套完整的预测模型,包括掘进速度、进度预测、刀具的磨损预测及经济分析,在它的施工进度预测模型中,考虑到了岩石的可钻性、孔隙度及岩体节理的密度及方向;QTBM模型源自于Q系统,加入了一些与隧道掘进机及与掘进速度相关的参数;概率模型是基于一个庞大数据库的类比模拟模型;模糊神经网络模型是一种黑箱模型,克服了输入与输出之间的不确定性关系。     

Effect of cutting tool blunting on the performances of various mechanical excavators used in low- and medium-strength rocks

Full-scale laboratory cutting tests that measure the specific energy (SE) are widely used to evaluate rock cuttability by mechanical excavators, and in particular roadheaders fitted with radial or drag-type bits. Radial or drag-type bits are often changed during operation as they wear and become blunt. In this study, full-scale cutting tests were carried out on different rock types using bits with varying degrees of wear in order to assess the impacts of pick bluntness on cutting forces and the SE. The relationships between wear flats and cutting forces, SE, and various rock properties such as uniaxial compressive strength, tensile strength, indentation index, Shore hardness, Schmidt hammer hardness, and density were examined and are discussed in this paper. The mean cutting force increased 2- to 3-fold and the cutting SE rose 4- to 5-fold with a 4-mm wear flat as compared to a sharp pick. Critical wear flats were plotted for different rock property values, and 25 MJ/m³ was considered the threshold SE above which cutting performance was considered to be poor. Best-fit predictive models based on statistical analysis of the laboratory cutting test results are introduced as a means to estimate SE as a function of bit type, wear condition, and various mechanical properties of the rock. These models can be used to predict the performances of mechanical excavators that use radial tools, especially roadheaders, continuous miners, and longwall drum shearers.     

Influence of rock mass fracturing on the net penetration rates of hard rock TBMs

Penetration rates during excavation using hard rock tunnel boring machines (TBMs) are significantly influenced by the degree of fracturing of the rock mass. In the NTNU prediction model for hard rock TBM performance and costs, the rock mass fracturing factor (k_s) is used to include the influence of rock mass fractures. The rock mass fracturing factor depends on the degree of fracturing, fracture type, fracture spacing, and the angle between fracture systems and the tunnel axis. In order to validate the relationship between the degree of fracturing and the net penetration rate of hard rock TBMs, field work has been carried out, consisting of geological back-mapping and analysis of performance data from a TBM tunnel. The rock mass influence on hard rock TBM performance prediction is taken into account in the NTNU model. Different correlations between net penetration rate and the fracturing factor (k_s) have been identified for a variety of k_s values.     

Clearance angle and evolution of depth of cut in actuated disc cutting

This paper investigates the effect of cutter clearance angle on variation of depth of cut and cutting process with an actuated disc cutting(ADC). ADC is a cyclic cutting method with two main characteristics:(i) a disk-shape cutter is used to attack the rock in an undercutting mechanism; and(ii) the cutter is dynamically actuated as it is moved across the rock. Hence, the cutting process of such system is periodic, each recurrence known as actuation cycle. The first ADC model, developed in 2016, represented an idealization of the technology with a flat disc cutter, where no clearance angle was considered. The evolution of the contact between the disc and the rock was, therefore, computed only on horizontal x-y plane, ignoring the effect of normal component of the force acting on cartridge. This article reports on a study that incorporates the cutter inclination angle in derivation of cutter/rock interface laws. It extends the proposed kinematic and geometry based model to take into account the variable depth of cut in estimating the forces associated with cutting in one actuation cycle. Experiments were conducted using Wobble to test the predictions of the improved model at various operating conditions. The model predictions are matched with the experimental results and effects of various factors are analysed.     

旋进式触探机制研究

 通过切削机制的引入,对角片式探头切削刃的受力进行分析,除建立轴向负荷与扭矩之间的数学模型外,还建立作用在探头上轴向负荷、扭矩与探头的运行参数(探入速度和旋转速度)及岩土体物理力学参数间的数学模型,并通过室内试验验证数学模型的存在性。根据数学模型分析轴向负荷、扭矩的影响因素,明确旋进式触探技术的理论依据：当机械运行参数,探头直径、材料及型式都相同时,轴向负荷和扭矩只与岩土体物理力学性质有关。将静力触探的轴向负荷与旋进式触探进行比较,从根本上解释旋进式触探技术能在岩体中得到应用的原因。