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.     

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.     

Air leakage measurement and analysis in duct systems

Air ducts and related equipments are used in a large number of buildings having thermal comfort. In this study, energy loss related with air leakage is studied. The leakage measurement setup was produced according to NEN-EN standards and the evaluation of data have been conducted by using power law model. The measurements were made on 300 and 1000 mm diameter single circular ducts, 300 mm × 250 mm and 1000 mm × 500 mm flanged joint rectangular ducts, 300 and 630 mm diameter circular beaded slip joint ducts, 300 mm × 200 mm and 500 mm × 300 mm rectangular flanged and drive slip joint ducts, and an branched air distribution system having different diameters for positive internal pressures. Test results have showed that the most of air leakage is from the joints. The seam contribution to air leakage is relatively lower than the joints. Using sealing gaskets help to improve the air leakage by about 50%.     

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.     

Experimental study of the effect of fracture size on closure behavior of a tensile fracture under normal stress

Tensile fractures that measured from 37.5 mm×37.5 mm to 260 mm×260 mm were created in sandstone perpendicular to the bedding plane by intending steel wedges, and closure of these fractures under normal stresses of up to 10 MPa was measured in the laboratory to investigate the effect of fracture size on closure behavior. Prior to the tests, the aperture distributions were determined by measuring the topography of the upper and lower surfaces using a non-contact surface profile measurement system with a laser profilometer, and the power spectral densities (PSDs) of the initial aperture and the surface heights were calculated by using a standard fast Fourier transform (FFT). The experimental results showed that at a given normal stress, closure significantly increases with an increase in fracture size. However, the relation between normal stress and closure, normalized by the standard deviation (SD) of the initial aperture, is almost independent of the fracture size, since the SD of the initial aperture also increases with fracture size. Thus, the size effect on the closure of a fracture under normal stress is governed by that on the SD of the initial aperture.     

Multiaxial tensile–compressive strengths and failure criterion of plain high-performance concrete before and after high temperatures

Multiaxial tensile–compressive tests were performed on 100 mm × 100 mm × 100 mm cubic specimens of plain high-performance concrete (HPC) at all kinds of stress ratios after exposure to normal and high temperatures of 20, 200, 300, 400, 500, and 600 °C, using a large static–dynamic true triaxial machine. Friction-reducing pads were three layers of plastic membrane with glycerine in-between for the compressive loading plane; the tensile loading planes of concrete samples were processed by attrition machine, and then the samples were glued-up with the loading plate with structural glue. The failure mode characteristic of specimens and the direction of the crack were observed and described, respectively. The three principally static strengths in the corresponding stress state were measured. The influence of the temperatures, stress ratios, and stress states on the triaxial strengths of HPC after exposure to high temperatures were also analyzed respectively. The experimental results showed that the uniaxial compressive strength of plain HPC after exposure to high temperatures does not decrease completely with the increase in temperature, the ratios of the triaxial to its uniaxial compressive strength depend on brittleness–stiffness of HPC after different high temperatures besides the stress states and stress ratios. On this basis, the formula of a new failure criterion with the temperature parameters under multiaxial tensile–compressive stress states for plain HPC is proposed. This study is helpful to reveal the multiaxial mechanical properties of HPC structure enduring high temperatures, and provides the experimental and theory foundations (testing data and correlated formula) for fire-resistant structural design, and for structural safety assessment and maintenance after fire.     

Field performance of concrete pipes during jacking in cemented sandy silt

Although many field investigations into pipe-jacking installation have been reported within the literature, there are few reports on the rebar stress in jacking pipes. This paper presents the field performance of concrete pipes during the jacking carried out under the Guan River in Jiangsu, China. Rebar stresses at two wings (the left and right side), the top crest, and the base in the longitudinal and circumferential directions for four different pipes were monitored. The maximum rebar stresses during the jacking were 37.1 MPa in the longitudinal direction and 36.6 MPa in the circumferential direction. However, the maximum rebar stresses after construction were only 18.5 MPa in the longitudinal direction and 20.3 MPa in the circumferential direction. A normalized jacking force “α” is proposed to evaluate the additional rebar stress in jacking pipes. The range of α is from 0.04 to 0.25. The relationship between the rebar stress and the construction procedure is presented and discussed. An excessive jacking force, an alignment deviation or an increased penetration rate would generate a large incremental rebar stress.     

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。     

Large-scale triaxial tests of dense gravel material at low confining pressures

The results of a series of large-scale triaxial tests performed on dense, prismatic gravel specimens, with a height of 50 cm and a cross-section of 23 cm×23 cm, are described. The specimens were prepared at a density equal to approximately 95% of the maximum density at the optimum moisture content. Deformations were measured locally using vertical and horizontal local deformation transducers. Stress conditions with selected levels of very low confining pressure were used to simulate specific conditions in the case of road and railway embankments. Particular attention was paid to the bedding error at the top and the bottom ends of the specimens, and to fixing transducers onto the membrane to be used under low confining pressure. The confining pressure was applied by vacuum and varied from 10 kPa to 75 kPa. Unsaturated specimens were tested under drained triaxial compression using monotonic and cyclic loading with frequencies in the range of 0.5–5 Hz. The effects of a large number of load cycles and of specimen preloading were investigated.     

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。     

Fracture behavior of a four-point fixed glass curtain wall under fire conditions

The cracking and subsequent fallout of glazing could significantly affect compartment fire dynamics by creating a new opening for air to enter. Twenty-four 1200×1200×6 mm³ soda-lime glass panes in eight different fixing forms were heated by a 500×500 mm² N-heptane pool fire to investigate the influence of fixing conditions on glass breakage and fallout. The time of crack initiation, behavior of crack propagation, heat release rates, central gas temperatures, glass surface temperatures and loss of integrity of the glazing assembly were investigated. The relationship between fixing form and crack behavior is discussed, based on the experimental results. The results show that all the cracks initiated at the supporting point and intersected rapidly, causing glass fallout. Mechanical stress caused by supporting pins and thermal stress caused by glass temperature difference (ranging from 48 °C to 159 °C) are the causes of breaking for this kind of curtain wall. It is concluded that various fixing locations have a significant effect on glass breaking. Among the eight cases, the glass panes whose supporting points were located at 10 cm (Case 1) or 5 cm (Case 8) from the edges performed best: these support locations are recommended in practical engineering because of the good fire resistance and structural beauty of such panes.     

Experiences of TBM operation in gas bearing water condition – A case study in Iran

The Nowsud tunnel (Lot 2B) project is a 25.7 km length water conveyance tunnel which was bored with a 6.73 m diameter double shield TBM. The tunnel consisting of 6.0 m inside diameter which lined with 25 cm thick, 4 pieces honeycomb precast segments. The geology is consisted of limestone, limy shale, black shale and Shally limestone of Cretaceous Garu and Pliocene Gurpi formations. During heading of tunnel, it was encountered with CH₄ gas emission and H₂S bearing water inrushes, up to 890 l/s. A source which could not be plugged with grouting and the heading had to be stopped for several days and months. As far as the author is aware, this condition has not been seen in double shield TBM tunneling.This case study attempts to discuss firstly the quality and origin of poison gases and water ingress into the excavations. Then, the destructive effects of the poison gases and water ingress on different parts of TBM, concrete corrosion, considerable delay in tunnel progresses and negative impact on tunnel personals productivity have been evaluated.Finally, with respect to restricted space in TBM and back up, a executable solution methods have been pursued to abatement and prevention of the poison gases and water ingress into the excavations, while the construction is in progress by double shield TBM.     

Effect of alkali-silica reaction and freezing and thawing action on concrete–steel bond

An experimental program was conducted to investigate the effect of stresses and cracks, caused by alkali-silica reaction (ASR) and freezing and thawing (F/T), on bond between reinforcing steel and concrete. Pullout test cylinders, reinforced with 18 mm steel bars, were used to evaluate bond behavior. Concrete prisms (50 × 50 × 300 mm) were also cast to evaluate expansion and reduction in ultrasonic velocity due to ASR and F/T cycles, respectively. Specimens were cured for 40 days before being either immersed in sodium hydroxide solution of 0.5 normality in order to accelerate ASR, or subjected to different cycles of F/T. Bond behavior, expansion, and ultrasonic pulse velocity tests were carried out as ASR progressed or under F/T cycles.The progress of ASR resulted in significant losses in critical bond stress and ultimate bond strength capacity reaching as high as 44% and 24%, respectively, accompanied by a significant increase in free-end slip at failure. The loss in bond due to ASR was higher for specimens prepared using concrete with lower concrete strength and higher percentage of reactive aggregate. F/T action caused a significant reduction in critical bond stress and ultimate bond strength that reached as high as 100% and 55%, respectively, and an increase in free-end slip at failure. Neither ASR nor F/T cycles affected trends in the behavior of bond stress versus free end slip curves.     

Some contributions on the estimation of performance and operational parameters of raise borers – A case study in Kure Copper Mine,Turkey

Excavation of shafts and other vertical structures in mining and civil engineering fields for material and human transportation and ventilation purposes is a difficult job taking quite long time to realize. Raise boring provides a safe means of excavating shafts between two levels of underground structures without using explosives. A Raise Boring Machine (RBM) operates by the principle of first drilling a small diameter pilot hole and then, reaming the hole in one or more stages to the desired size. Raise boring system is the most up-to-date, secure and fast way for boring large diameter shafts. This paper concerns about the estimation of the performance and operational parameters of a RBM used to excavate ventilation shafts in a copper mine located at the city of Kastamonu, Kure Province, on Northern Turkey. Length and diameter of the ventilation shaft are 22 m and 2.6 m, respectively. Borehole samples were collected during pilot hole drilling operation for performing physical and mechanical tests in the laboratory. Excavation performance parameters of RBM such as, penetration rate, cutterhead torque, and total thrust force were theoretically estimated based on the experimental results. Then, the realized and predicted values were compared to serve a useful guide for future applications. The main points emerging from this study is that Tunnel Boring Machines (TBM) and RBM cuts the rock applying the same basic principles of rock cutting mechanics. Specific energy values for both machines are in the same order for similar depth of cut and similar rock formation enabling to predict penetration rates of RBM from huge data of TBMs already published in the literature. It is also proved that the thrust forces for RBM may be predicted in massive rock as it is done for TBM based on projectile area of the cutter and rock compressive strength.     

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。     

Slate flexural and anchorage strength considerations in cladding design

This paper describes an experimental investigation on the flexural and anchorage strength of slate for cladding. The study has been conducted on sawed slate specimens, all showing the same surface finishing. Slate flexural strength was compared for two distinct situations: (i) using a 3-Point flexure loading configuration in batches of materials with larger cross-sectional specimen dimension (50 × 30 mm²); and (ii) using a 4-Point flexure loading configuration in the same batch of materials but with smaller cross-sectional dimensions (30 × 25 mm²). The 4-Point bending specimens were tested in three different directions considering slate anisotropy planes. Load was applied along the direction perpendicular to the planes of schistosity; and also along two directions parallel to the planes of schistosity. Slate anchorage strength has been determined on slate slabs with 400 × 200 × 30 mm³ with dowel anchorage in 8 mm diameter cylindrical holes with 35 mm depth. Test load was applied perpendicularly to the schistosity planes. Cladding stone in building facades and its supporting systems must be compatible with the behaviour and performance of other interfacing systems, such as curtain walls and superstructure frames. In this sense, a properly executed dimensional stone cladding should be designed and installed within the capabilities and limitations of the slate’s support system to resist all active forces or actions. The results of this work reveal the importance of complementary characterization techniques for dimension stone cladding, particularly for anisotropic rocks as slates. From the results it is possible to conclude that schistosity planes have an utter influence on either anchorage or flexural strength.     

Design considerations for an underground room in a hard rock subjected to a high horizontal stress field at Rana Gruber,Norway

Rana Gruber AS is an iron mining company in the North of Norway, and it operates Kvannevann mine 30 km east of Mo i Rana. The Kvannevann mine is located in a foliated gneiss host rock, with an ore body about 70 m wide and more than 300 m deep. The mine has been in operation for many years using sublevel stoping, and is now changing to sublevel caving. Experience from past mining activity in the infrastructure preparation for the new mining method indicates that the mine is located in a hard, brittle rock mass with high horizontal stresses. Stress measurements have been made from time to time. The measurement results indicate a major principal stress of 20 MPa perpendiculars to the strike of the ore, and a minor principal stress of 10 MPa parallel to the strike of the ore, which is 10–15 times higher than the theoretical vertical stress caused by gravity at the measured location. In addition to the high horizontal stress, lessons learned regarding failure and rock support during the underground excavation need to be considered for designing and excavating a new canteen room (B × H = 9 × 8 m) at the mine. Numerical modelling is utilised to be able to include all of the adverse conditions for consideration.     

Residual compressive behaviour of pre-heated high-performance concrete with blast–furnace–slag

An experimental program was designed and carried out to study the residual compressive behaviour of high-performance concrete (HPC) with blast–furnace–slag (BFS) at elevated temperatures ranging from 20 to 800 °C. The residual cube compressive strength is examined and the relationship between the residual compressive strength and temperature is investigated based on the heated cube specimens (100×100×100 mm³) tested on a universal test machine. In addition, on the basis of the heated prism specimens (100×100×300 mm³) tested on an electro-hydromantic rigidity servo test machine, the complete stress–strain curves are obtained, and the effects of temperatures on the residual prism compressive strength, the strain, and the elastic modulus etc are analysed. An approximate formula for the stress–strain relationship of HPC–BFS after exposure to temperatures is proposed.     

Improvement of residual compressive strength and spalling resistance of high-strength RC columns subjected to fire

This paper investigates the spalling properties of high-strength concrete in order to improve the residual compressive strength and spalling resistance in specimens subjected to 3 h of unloading fire conditions. This study consists of three series of experiments with eighteen different specimens varying in fiber type and content, finishing material and simultaneous fiber content and lateral confinement. They were fabricated to a 300 × 300 × 600 mm mock-up size. Results of the fire test showed that the control concrete was explosive, while the specimens that contained more than 0.1 vol% of polypropylene (PP) and polyvinylalcohol (PVA) fibers were prevented from spalling. One specimen, finished by a fire endurance spray, exhibited even more severe spalling than the control concrete. The specimen containing 0.1 vol% of PP fiber and using a confining metal fabric at the same time, showed the most effective spalling resistance; in particular, the residual compressive strength ratio was even higher than that of the control concrete before the fire test. It was demonstrated that adding fibers in concrete prevented the spalling occurrence and confining metal fabric around the main bars of concrete specimens can secure the strength of structures during the conditions of elevated temperature.     

Experimental research on water retention and gas permeability of compacted bentonite/sand mixtures

Highly compacted bentonite-based materials are often considered as buffer or sealing materials for deep high-level radioactive waste repositories. In situ, the initial state of bentonite-based materials is only partially saturated, which has a very high suction that will promote water absorption from the host rock. In addition, a gradient of water saturation will be formed between the external part and the central part of the compacted bentonite blocks. In this paper, water retention tests, under both constant-volume and free-swelling conditions, were performed to investigate the suction behavior of a compacted bentonite/sand mixture. In order to investigate the sealing ability of the partially saturated bentonite/sand mixture, gas permeability tests were also carried out under the in situ confining stress. It was found that the confining conditions have a limited effect on the water retention capacity of the compacted bentonite/sand mixture at lower levels of relative humidity (RH), while this influence is significant at higher RH levels. The results of gas permeability tests show that gas permeability is very sensitive to the water content and the confining pressure. When the sample (stable at RH=98%) was subjected to a in situ confining pressure (7–8 MPa), the gas permeability was very low (1.83×10^–14 m/s) which indicates that gas tightness can be obtained even though the sample is not fully saturated.