Kayaçların kazılabilirlik ve jeoteknik özelliklerinin kollu galeri açma makinelerinin kazı hızları üzerindeki etkilerinin incelenmesi

Abstract

ÖZET Madencilik ve inşaat sektörlerinde uzun yıllardır kullanılan klasik galeri-tünel açma yöntemi (delme-ateşle me yöntemi); ilerleme hızının sınırlı olması, işgüvenliği ve tahkimat, konularında ortaya çıkan sorunlar nedeniyle önemini kaybetmiştir. Belirtilen sakıncaları giderebilmek amacıyla kazının makine ile yapılması düşünülmüş ve bu ko nuda yoğun araştırmalar başlatılmıştır. Elde edilen bulgu lara göre, makine ile galeri-tünel açmada başarı sağlana bilmesi için kazılacak kayaç ile ilgili jeomekanik özellik lerin çok iyi bilinmesi gerekmektedir. Ancak, bu özellik - lerden hangisinin daha önemli olduğu, birbirine ne şekilde etkilediği hâlâ tartışma konusudur. Bu araştırma İstanbul'da kanalizasyon amacı ile açı - lan Haliç Tünel.' inde sürdürülmüştür. Tüneldeki kazı işlemi şildli bir kollu makine ile gerçekleştirilmektedir. Yerin de yapılan çalışmalarda, makine performansının yanısıra, aynanın süreksizlik durumu (RQD değeri) saptanmış, Schmidt Çekici ve Beton Tabancası ile ölçmeler sürdürülmüştür. Laboratuvar çalışmalarında kayaçlar ın jeomekanik özel likleri saptanmış, bu özelliklerden birbiri ile ilişkileri ve makine performansına etkisi araştırılmıştır. Ayrıca, yanal basınçların ve basınç yönünün kesme parametreleri üzerindeki rolü incelenmiştir. Sonuç olarak ; Schmidt Çekici ve Beton Tabancası değer leri ile laboratuvarda saptanan kesme enerjisi değerinin makine performansını en iyi yansıtan veriler olduğu saptan mıştır. POD değeri ve kayaçların sertliğini simgeleyen ö zellikler birlikte ele alındığında makine ilerleme hızını daha anlamlı bir şekilde ifade etmek mümkündür. viii

SUMMARY INVESTIGATION INTO CUTTABILITY CHARACTERISTICS OF ROCKS AND GEOTECHNICAL FACTORS AFFECTING THE ADVANCE RATES OF ROADHEADERS The need in the amount of underground excavation in mining and civil engineering field is increasing rapidly. Specially in coal mining it is estimated that a total amount of roadways of 19200-22400 km has to be driven every year. The economic charge of this work is around 115 - 135 x 109 DM. if the other underground excavation activities in mining and tunnelling are to be taken account, we are faced with an expenditure exceeding the annual budget of the most countries. This clearly emphasizes the importance of any improvement in roadway drivage techniques. Any underground excavation is realized either by drilling and blasting or mechanized cutting methods. The second method has many advantages upon the first; these are being, the economy, high advance rates and less overbreak. The chock vibrations are also eliminated, when roadheaders are used. It must be strongly emphasized that all these advantages are realized if the roadheaders are selected according to te cuttabili-b/ properties of the rock formations. Furthermore the initial investment, assembly and disassembly costs of these machines are rather high, these make the minimum length of tunnel to be driven at once very critical. In other words any success of the roadheaders depends on the geotechnical properties of rock formations in addition to the human and machine factors. Because of the limited information available on roadheader performance in different ground condition prediction of likely rates of advance is difficult. In particular, data on the cuttability of rock materials is required to improve prediction of roadheader performance. In order to investigate the factors affecting machine performance and to predict advance rates, a major research project was carried out in the mining Faculty of Istanbul Technical University. The widerspread use of the uniaxial compressive strength test to predict rock cuttability and abrasivity has often proved to be inadequate highligting the need to determine the influence of rock material and rock mass properties on tunnelling machine performance. Tunnel boring machines may be classified as full face machines and boom type roadheaders. Emphasis has been placed recently on the development and use of full-face ixtunnelling machines, these may be work succesfully in any hard rock formations, but they are limited to producing circularopenings. A circular opening for a large roadway could result in the excavation of considerably more rock than is really necessary and producing a space that cannot be easily utilized. Roadheaders are the type of tunnelling machine that is in widest use today in underground mining operations. They have been developed withing the European coal-mining industry to excavate multiple access to production area. As a result they employ a flexible cutting boom which unable them to selec tive excavation of mineral bands and to cut different sizes and shapes of tunnel. Disc cutters are the most commonly used tool for full- face tunnelling machines. Design and metallurgical improvements have jointly contributed to the development of the present-day toothed roller cutters in use in blast hole drilling and in the oil industry. Such cutters are now in common use on tunnel boring machines. Picks are the primary excavating tools in coal mining since they are widely used in shearers, ploughs, roadheaders etc. and are gaining application in harder and more abrasive rocks. Picks are more susceptible to wear than any type of roller cutters since each point on the cutting edge is in continu ous contact with rock. Water spraying systems are generally used with these type of cutters for cooling, this decreases in great quantity the wears of picks. The cutting spead is also limited in order to decrease the wear. Many research works are being carried out in order the increase the productivity and the performance of roadheaders. Water assisted jet cutting is in a prime concern. It is claimed that some cammerically available water assisted roadheaders may successufully cut even hard rock formations having a compressive strength up to 1^0 MPa, this covers mainly all the coal measures stones. It is also claimed that a water jet prersure of 20-140 MPa is necessary for a succesfull excavation. Water jet is also advantageous for supressing dust generated from cutting operations, and cooling overheated cutters. Many studies are also being carried on improving the design of cutting booms, the computer assisted cutting head design being the most investigated subject. Many laboratory and insitu testing methods are used for rock cuttability determination. Roxborough in his recently published article emphasized on the importance of direct and indirect testing methods, rock mass properties and rock abrasivity on the rock cuttability of rock forma tions. However Ghose's machineability classification of rock sfrata mainly included, rock abrasivity, point load strength index, briteleness, kiruna factor and water income. The insitu testing methods may be mainly mentioned as; M.R.D.E. penetrometer, expanding bolt seam tester, expanding wedge tester, insitu rock cutting machine, drillability test and Schmidt hammer test.Laboratory rock cutting experiments are considered to be most successful in predicting the roadheaders cutting performance. In order to investigate the main factors governing the insitu and laboratory rock cutting mechanism a laboratory rock cutting rig has been developed for our research work. A 15 kw shaping machine was used to conduct the experiments. This has a maximum stroke of 600 mm, a speed range of 0.15 - 0,65 m/sec and a work table which could be raised, lowered and traversed horizantally. The experimental cutting tool which has -5° rake angle and 5° clearance angle is clamped in the tool holder of a Kistler 9257 A model piezoelectric dynamometer. The output from the dynamometer is amplified using a Kistler 5001 type charge amplifier and Kistler 5211A type galvo ampli fier system and a Bryans Ultra Violet Chart Recorder. In the process of chip formation, there are wide fluctua tions of forces. In a recorded trace a peak force corres - ponds to a chip formation. The mean values are obtained by calculating the area between peak and minimum forces fey a planimeter. Using this technique, specific energy, cutting and normal force components acting on cutting tool were recorded using different rock samples taken from Halic Tunnel and Amasra Coalfield. Specific energy is defined as the work done to excavate a unit volume of rock, and it is obtained by dividing the mean cutting force by the volume of the material excavated per unit distance cut. Satifactory calibration results for measuring systems have been obtained prior to rock cutting experiments. Halic Sewer tunnel was choosen as a pilot tunnel in order to carry out insitu measurements and to investigate the geotechnical factors affecting roadheader performance,. Analysis of shift data, overall machine performance and geotechnical properties of the rock formation in the zones examined are first detailed and later a statistical analysis has been carried out in order to find a correlation between machine cutting performance and rock mass properties. Halic Tunnel is a part of a new combined interceptor sewerage system for south Halic. The project is prepared by Istanbul Water and Sewerage Autority (ISKI) to renew the inadequate sewerage network of Istanbul and to clean the very polluted Golde n Horn. The tunnel has a length of 2640 m. and an external diameter of 3270 mm. Tunnelling activities are carried out with a 3 shifts a day working programme. One shift is usually consisted of 17 men. Shield mounted German Herrenknecht Roadheader was used throughout tunnelling operations. The machine is supplied with 95 H.P hydraulically driven booms given a variable cutting speed of up to 90 rev/min and cutting boom is built as an integral part of shield body. The roadheader was equipped with methane detectors. The tunnel lining erector has also proved fast and sensitive. Exhaust ventila tion is provided by a 50 cm diameter fan and plastic pressure ducting to the surface. A supply of fresh air was also introduced behind the machines. Precast concrete segments for supporting systems were cast in the site casting plant. The same plant supplied also the necessary xiamount of concrete for the secondary lining. An inner pvc protection lining is also supplied in the inner crown of the tunnel. During Halic Tunnelling operations a total amount of 26500 m3 rock material was excavated and an amount of 3634 pick cutters was used, the economical charge of this pick consuption is around 2380 TL/m3 (2 #/m3). An average machine available time of 78 %, operating time of 74 I, machine reliability factor of 22 % and utilisation factor of 60 % were recorded th.rougho.nt the tunnel excavation. Rock formations of carbonne fferous age are found in the area, these are fine to coarse graine strongly fractured muds tone, shale, sandstone and conglomerate. Some diabase dykes have also been encountered while driving the tunnel and these affected pragress rate as they have been significantly harder than rock being excavated along majority of the route. It was strongly taken care of col lecting data covering all the geological conditions. It is widely accepted that when measuring strata properties, insitu characteristics and the intact strength of the rock are required. The insitu rock mass property which has the most influence on cutting performance is discontinuity spacing and this may be measured by a system known as R.Q.D. For our research studies these values were calculated from discontinuity spacing throughout the Halic Tunnel using- the formula RQD = 115-3,5 Jv, RQD si 100 Jr< 4.5. This equation is suggested by International Society of Rock Mechanics in the case of borecore is unavailable. In this equation RQD is rock quality designation and Jr is volumetric joind count. The calculation of Jr is based on the mean spacing. The occasional random disconti- nuties does not noticeably affect the value Jr unless the spacing of the systematic joints is wide or very wide (i.e 1.10 m). Thin sections prepared from rock samples belonging to Halic Tunnel were carefully examined under microscope for abrasive mineral determination. It is found that quartz content of the samples were high. The samples were also subjected to a wide range of physical and mechanical tests including the uniaxial and triaxial test, tensile strength, elasticity modulus, ultrasonic wave velocity. It is found that the density of the samples ranged from 21.1 to 28 kN/m3, porosity from 1,3 % to 6,2 %, impact strength index from 81.9 to 88.6, cone indenter hardness from 1.15 to 8.73, point load strength index from 1.42 to 7.18 MPa and sclerescope Hardness from 26,3 to 81.9. The previously developed relationships by the N.C.B. research workers between the uniaxial compressive strength ^c and cone indenter hardness Is was also found to be valid for rock formations encountered in Halic Tunnelling Side? i.e. 0C = 24.8 Is. Statistical analysis carried out on rock cutting test results shoved that specific energy values were well xiicorrelated with coarseness index, shore sclerescope hardr nes, ultrasonic wave velocity and point load strength in dex values respectively. Specific energy values were found to be varry between 18 and 39 Mj/m3, these being upper limits for the application of roadheaders. Laboratory test results were found not to be very suitable in predicting roadheader cutting performance, therefore some insitu testing methods were also included in the research programme. An Impex impact penetrometer and N type Schmidt hammer were used for this purpose, the values changed from 20 to 65 for Schmidt hammer and from 1.7 to 7,7 cm for impact penetrometer. Penetrometer was found to be very suitable in giving the insitu strength properties of the rock formations. Further tests carried out on concrete blocks showed that penetrometer values were well correlated with uniaxial compressive test values, this equation being y= 70-0,059 x;.y being the penetrometer value in cm and x compressive strength in MPa. The effect of sideways and font'vrays confining pressure on rock cutting parameters were also.investigated carefully using core samples from Amasra coalfield and block samples from Halic Tunnelling Side. From this investigations it is conluded that sideways confining pressure has a conclusive effect on pick cutting and normal forces and also on specific energy values. However in frontways confining pressure the cutting parameters were found to decrease. Thereafter the cutting test conditions are standardized according to these results. The results are also verified using Schmidt hammer and stressed cock Samples under testing machine. Machine advance rate was carefully recorded during tunnel drivage operations and the net cutting rate was found to be varry between 2 and 23 m3/h. Furthermore a statistical analysis has been carried out in order to find a correlation between machine cutting performance and rock geotechnical properties. For many years the most common means of assesing the likely performance of boom tunnelling machines were the use of uniaxial compressive strength, however it has now shown that in many cases specially in high fractured and jointed rocks compressive strength alone does not give a good indication of rock machineability, rock quality designation (R.Q.D) being the most dominant factor in these conditions. A linear relationship is found between R.Q.D. and machine cutting rate. Specific energy values are also correlated well with cutting rates, the equation being SE = 44.75 - Q/0,8, in this equation S.E. is in Mj/m3 and Q in m3/h. Schmidt hammer and impact penetrometer values are also related lineerly to machine advance rates, however if R.Q.D. values are combined with previously mensioned rock properties, the correlation coefficient of the statistical relationship improved con siderably. The correlation coefficients between roadheader cutting xiiirate and some intact rock properties were found to be poor, these properties are uniaxial compressive strength, tensile * strength, ultrasonic wave velocity, Shore Sclerescope, point load strength index, cone inden ter hardness and impact strength index. However as previously mensioned the correlation coeffi cients of these relationships improved notably when R.Q.D. values are combined with these intact rock properties. This thesis is imainly concerned with the geotechnical factors affecting roadheader performance^ Halic Sewer Tunnel. It is mainly concluded that rock mags cuttability index defined as a product of rock properties and R.Q.D. is the main factor governing the roadheader advance rate, it is,. also concluded that accumulated data and the relationship established will serve as a useful guide to engineers and machine manufacturers prior to any new tunnel project in Istanbul or elsewere. xiv