1.Introduction of Geo-technology and Geology

Definition of Geology:

Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how Earth’s materials, structures, processes and organisms have changed over time.

Geo-technology in Construction(Tunnelling):

The problem of Civil Engineering has generally been seen either to relate to "Design" or to "Construction". Research in Civil Engineering Design has often been taken to mean the study of some static scenario so as to eliminate unwanted behaviour. Research in Civil Engineering Construction has often been taken to mean the study of management techniques for the control of construction activities.

The new challenge is to relate Design to Construction, which requires a study of the Technology used to create some facility. Spin-off should include the optimisation of construction processes, and the development of new technology, including:

minimising errors and stoppages caused by unforeseen conditions; maximising the robustness of equipment in the widest variety of ground conditions; minimising the capital cost of equipment; maximising the speed of construction; minimisingthe disturbance to neighbours, or to the environment.

Compensation grouting - the injection of grout during tunnel construction, at an intermediate level between ground surface and tunnel crown, to eliminate subsidence and collateral surface damage - has been under investigation. The basic mechanism of hydro-fracture, widely used for compensation grouting, is underongoing study, together with the global plastic mechanisms which control subsidence at the ground surface.

Various civil engineering structures are constructed every year around the world aiming to improve several aspects of our increasingly advanced lifestyles. Large-scale civil engineering structures such as dams and tunnels are often undertaken by the government, local councils, or large utility suppliers. For projects of that scale the quality and safety planning required are rated of high priority.The foundation supporting a civil engineering structure is the most important element of the structure, and will have an affect on the quality, safety and construction costs of the project. Usually, the geotechnical properties of the foundations are determined through engineering geological surveys and ground investigations, prior to construction and will, in some cases, guide the planning and design.However, it is difficult to determine the ground conditions at the required accuracy from primary geological surveys, especially when the project is a deep underground structure, which spans along an extensive area, and encounters complex geological structures. Carrying out the construction without sufficiently understanding the ground conditions may lead to small or large failures and fatal accidents. Therefore, it is considered important to

carry out geological survey prior as well as during the construction in order to monitor the ground behaviour and obtain adequate information for the construction. The raw geological and geotechnical information obtained from a ground investigation are not always directly useable from the engineer. It is therefore important for the engineering geologist to interpret the geotechnical information obtained and in a way translate it in the language of the engineer. It should be clear however from an early stage the purpose of the ground investigation in order for the appropriate methods to be used to obtain the ground properties in question.

History of geo-technology:Humans have historically used soil as a material for flood control, irrigation purposes, burial sites, building foundations, and as construction material for buildings. First activities were linked to irrigation and flood control, as demonstrated by traces of dykes, dams, and canals dating back to at least 2000 BCE that were found in ancient Egypt, ancient Mesopotamia and the Fertile Crescent, as well as around the early settlements of MohenjoDaro and Harappa in the Indus valley. As the cities expanded, structures were erected supported by formalized foundations; Ancient Greeks notably constructed pad footings and strip-and-raft foundations.The application of the principles of mechanics to soils was documented as early as 1773 when Charles Coulomb (a physicist, engineer, and army Captain) developed improved methods to determine the earth pressures against military ramparts. Coulomb observed that, at failure, a distinct slip plane would form behind a sliding retaining wall and he suggested that the maximum shear stress on the slip plane, for design purposes, was the

sum of the soil cohesion, c, and friction , where is the normal stress on the slip plane and is the friction angle of the soil. By combining Coulomb's theory with Christian Otto Mohr's 2D stress state, the theory became known as Mohr-Coulomb theory. Although it is now recognized that precise determination of cohesion is impossible because c is not a fundamental soil property,[6] the Mohr-Coulomb theory is still used in practice today.

2. ROLE OF GEOTECHNOLOGY IN PLANNINGEach tunnel project is unique! This paper provides broad-based guidelines for the conduct and use of siteinvestigations for planning and design of tunnels. It provides an overall approach or perspective rather than cookbook solutions. Inflexible rules or cookbook solutions often work for some situations in design of civil works but not in geotechnical investigations. This paper, which is intended for owners, as well as the planners, engineers and contractors, concentrates primarily on the aspects of geotechnical issues and investigative methods, which are important to tunnelling. Much of this paper is based on tunnelling practice in the United States but the concepts and procedures are applicable worldwide with appropriate modifications for local conditions and methods. For the tunnel designer and builder, the rock or soil surrounding a tunnel is effectively a construction material. Think of it this way; when the excavation is made, the strength of the surrounding ground keeps the hole open until the tunnel supports are installed. Moreover, even after the supports are in place, the ground, through arching, continues to provide a substantial percentage of the total load-carrying capacity.

The geology along a tunnel alignment plays a dominant role in many of the major decisions that must be made in planning, designing, and constructing a tunnel. Geology dominates the feasibility, behavior, and cost of any tunnel. Although difficult to appreciate, the engineering properties of the geologic medium and the variations of these properties are as important as the properties of the concrete or steel used to construct the tunnel structure. In a tunnel, the ground acts not only as the loading mechanism, but also as the primary supporting medium. Thus, it is vital that the most appropriate geotechnical investigation is conducted early in the planning process for any tunnel.

3. WHEN TO CONDUCT GEOTECHNICAL INVESTIGATIONSThe sooner that geotechnical information is obtained and evaluated, the greater the potential for optimization of the alignment and profile and for greater cost savings. The abundant geotechnical uncertainty requires tunnel exploration and design to be iterative. Without reliable geological information, planning decisions may be incorrect.The author is aware of numerous cases where tunnel projects benefited because either the horizontal or vertical alignment was dramatically changed as a result of geotechnical information.The planning of each exploration phase should be based on the results of the previous phase. Most importantly, the geotechnical exploration, including evaluation and report, must be available to the decision makers on the design team in a timely manner.Significant geotechnical work will be necessary during the early portions of preliminary and of final design interspersed with relatively low levels of effort. During the latter stages of final design when contract documents are finalized, there should be a significant geotechnical effort to support the preparation of the Geotechnical Baseline Report (GBR) and the rest of the contract documents. A genuine need for geotechnical input then extends into the bidding, construction, and post-construction phases.

Selected Challenges of the Underground:• Underground projects have vast uncertainty• The cost, and indeed feasibility, of the project is dominated by geology• Every aspect of the geologic investigation for tunnels is more demanding than investigations for traditional foundation engineering projects• Regional geology and hydrogeology must be understood• Groundwater is the most difficult condition/parameter to predict and the most troublesome during construction• The range of permeability is significantly greater than the range of any other engineering parameter (roughly 10-7 to 10+3 a factor of 10,000,000,000)• Even comprehensive exploration programs recover a relatively minuscule drill core volume that is less than 0.0005 percent of the future excavated volume of the tunnel• Engineering properties change with a wide range of conditions, such as time, seasons, rate and direction of loading, etc.; sometimes drastically• It is guaranteed that the actual stratigraphy, groundwater flow, and behavior observed during construction will be compared to your predictions.

4. TUNNELLING GEOLOGICAL INFORMATION EVALUATION TECHNIQUEIt is important to predict the likely geological conditions ahead of the tunnel face. Various techniques are available to assist in these kinds of predictions. When the survey results are being utilized, the accuracy and reliability of the investigations must be evaluated sufficiently, because the characteristics of these investigations may vary by investigation principle or by characteristics of the research objects. Generally, the geological properties of a tunnel are complex even though the ground conditions of adjacent tunnels may be alike. Therefore, evaluation of the ground investigation results should be performed for every tunnel.It is often possible that the obtained geotechnical classification based on the ground investigation, results are often not as good as required for the construction. Considering that the most important thing is the usability of the obtained geological information for tunnel construction, the ground investigation purpose should be established beforehand, and evaluation classification of the survey results should be done accordingly. By accumulating the data on the characteristics of each geological survey method it is possible to use the geological information more rationally.The ground investigation flowchart for geological evaluation under tunnelling is shown in Figure.

Case study:The condition of headrace channel tunnel with large water inflow occurred under tunnel excavation is shown in Figure(Shiozakiet al., 2000). In this case the water inflow arose near the fractured zone which was not observed during the ground investigation, causing the tunnel face to collapse putting the excavation on a halt, introducing financial implications.

Furthermore, the amount of oxygen dissolved in the water inflow was rather small and the oxygen concentration in the tunnel was temporarily lowered to 16%, causing safety

construction problems

5. CASE STUDY OF TUNNELING INFORMATION: The outline of the case study of tunnelling information Utilization of geological information based on TBM machine data Geological structure prediction by seismic reflection method (called

TSP method)

The outline of the case study of tunnelling information: Case study on various ground investigation methods during tunnel construction was carried out in order to confirm the suitability of the evaluation flow. In this case, the established purpose of the ground investigation was to ensure the quality and safety under tunnel construction. Therefore, all geological structures supposed to be effective for quality and safety of the tunnel under construction, such as faults, fractured zones, water contained zones, large-scale cavities etc., became the researched survey object. And, the scale of fractured zone was supposed to be equivalent to the tunnel cross section as several metres width.In this case study, the researched survey method includes a technique for estimating ground conditions near the tunnel face under construction by continuously collecting machine data of tunnel boring machines (TBM), as well as a technique for predicting geological conditions ahead of the tunnel face by TSP (Tunnel Seismic Prediction) method – a kind of seismic reflection method carried out in tunnel. Furthermore, based on obtained geological information from that survey, the tunnelling method is also examined.

Utilization of geological information based on TBM machine dataOutlines of utilization of geological information based on TBM machine data:The TBM (Tunnel Boring Machine) method is defined as machine controlled excavation of full cross section tunnelling method. Since the TBM method enables a tunnel progress of several decade meters, a rapid tunnelling construction is possible compared to conventional method. Typical features of the TBM method are as following:Since excavation cross section of the tunnel is of a round shape, the stability of the tunnel wall is high due to the arch effect; As the excavation energy is dispersed, there would be less damage to the tunnel wall.Therefore, the TBM method is a rational tunnelling method because the tunnel support work is minimum. However, the disadvantage of the TBM method is that it is unable of conducting geological observation of the tunnel face because the cutter head is fixed with a disk cutter, which is pressing against the tunnel face during the excavation. And keeping the excavation without understanding the change in the geology of the tunnel face may cause collapse of the tunnel face and the tunnel wall. On the other hand, auxiliary method for stabilizing the tunnel face, like the forepiling is difficult, while simple investigations such as drilling are also often constrained by construction space.In excavation and construction of a tunnel using a TBM, the risk of accident is existed, though there is a merit for quality assurance, etc… Therefore, it is important to reduce the risk of the TBM method by clarifying the ground conditions around and ahead of the tunnel face, and incorporating this information in the construction management plan.Considering that the excavation abilities of a TBM are related to the ground conditions of the tunnel, Fukui et al. (1997) had undertaken an advanced study to clarify tunnel geological conditions from TBM machine data. He resultedthat the selection of the parameters used in the geological evaluation had not been found reasonable, and the usage tothe construction has not yet been established.Geological characteristic evaluation according to TBM machine data:In evaluating the ground conditions according to the TBM machine data, each machine data item is subjected to examination. The excavation function of the TBM consists of drilling, by rotating of the cutter head, as well as a driving mechanism that promotes TBM machine ahead while promotion reaction force supports construction. During excavation, machine data are acquired. Within the acquired raw data, the following data were examined:Cutter electric current: current of the cutter head rotating motorPure penetration rate: intrusion speed of the cutter headThrust: pressure of the promotion jackBearing capacity: oil pressure of gripper jack which ensures reaction forceFurthermore, examination was performed on following parameters, whose values were calculated from multiple raw data.Rock mass strength Excavation energyWork volumeRotational energy.Still, it is necessary to remind that the TBM machine data are affected by the field conditions, including the interaction of excavation and rotation, the resistance by the TBM main body and the vehicles for power supply equipment, the artificial control by the operator, etc.

Tunnel Boring Machines

TBM:Tunnel construction by means of TBM (Tunnel Boring Machine) has become a preferred method of construction nowadays. In addtion, this is well accepted by the environmentalist and the green groups. This state-of-art technology limits all works underground in building the tunnel to keep the distrubance to land, wildlife and mankind activities at ground level to a minimum throughout the period of construction.Tunnel construction by TBM is quite different from the traditional Drill and Blast Method.The tunnel is excavated by means of a machine instead of blasting with explosive. The tunnel lining is put in place at the back of the machine immediately following a ring length of TBM advancement. A well thought engineering survey scheme is devised to integrate with the operating system and working sequence of the TBM.For the TBM tunnel of the Lok Ma Chau Spur Line, firstly the TBM took a break in from thelaunching shaft at SheungShui and travelled 1.7Km to reach Kwu Tung East. The TBMmoved ahead 300m by jacking and took a second break in from Kwu Tung West and travelled another 1.4 Km to reach the extraction shaft at Chau Tau to complete the down track tunnel.

Tunnels under seismic loading: a review of damage case histories andprotection methods:INTRODUCTIONFor a long time it has been generally believed that earthquake effects on underground structures are not very important. This is because these structures have generally experienced a low level of damage in comparison to the surface engineering works. Nevertheless, some underground facilities were significantly damaged during recent strong earthquakes (Hashashet al.2001).In modern urban areas, underground space has been used to store a wide range of underground structures. Most underground structures are essential to human life and include many utilizations: pipelines for water, sewage, gas, electricity and telecommunication; subways; underground roads. For these reason it is very important to study how tunnels are damaged during earthquakes to protect human life and the service efficiency.

CASE HISTORIES COLLECTIONVery few data are available concerning damage to underground structures and tunnels after earthquakes before 70’s. In fact damages and failures were accurately documented only after strong earthquakes: after San Fernando earthquake (1971), ASCE (1974) published some data about the damage to underground structures in the Los Angeles area. Moreover

in many cases an accurate monitoring of lining cracks existing before the earthquake was missing.Therefore the real damage suffered by structures during the earthquake was unknown.After 1974 a systematic data collection of tunnel damages concerning different earthquakes was carried out, for the purpose of recognizing common features and similar causes.

Dowding&Rozen(1978) collected 71 cases of damage concerning both American (7) and Japanese (6) earthquakes. Such a database includes both railway and roadway tunnel and

water pipelines. Most of the cases are in compact rock (12), other in fractured rock (11) and only 3 cases concern tunnel in soil.Owen & Scholl (1981) updated the work by Dowding&Rozen, collecting 127 cases of damage to underground structures. An important adding came from the cut-and-cover tunnels damaged during the San Francisco (1906) and San Fernando (1971) earthquakes. These structures were shallow and generally constructed in poor soil.Sharma & Judd (1991) enlarged the collection of the previous Authors reaching a total number of 192 cases for 85 different earthquakes. To correlate seismic vulnerability of a tunnel to some relevant factors, six parameters were examined: tunnel cover, subsoil type, peak ground acceleration, magnitude of the earthquake, distance from the epicentre and type of lining support. Most of the damages (60%) affect shallow tunnels (depth lower than 100m); Many cases (42%) concern unlined tunnels in rock.

CRACK DISTRIBUTION ALONG THE TUNNEL LININGWang et al. (2001) suggest several patterns of cracking induced into the tunnel lining during an earthquake The six patterns are (Fig.):a) Sheared off lining: it occurs for tunnel passing through active faults;b) Slopes failure induced tunnel collapse: it occurs when the tunnel runs parallel to slopes generating landslides passing through the lining;c) Longitudinal cracks: it occurs when the tunnels subjected to higher deformations dueto surrounding ground;d) Traverse cracks: it occurs when the tunnel has weak joints;e) Inclined cracks: it occurs for a combination of longitudinal and transversal cracks;f) Extended cracks: it occurs when there is the partial collapse of linings for seismic intense deformation;g) Wall deformation: it occurs when there is a transverse reduction due to the invert collapse;h) Spalling of lining: it occurs when the transversal section completely collapses.

Types of damage: sheared off lining (a); slopes failure (b); longitudinal cracks (c); transversecracks (d); inclined cracks (e); extended cracks (f); wall deformation (g); spalling of lining (h)

The behaviour of a tunnel is sometimes approximated to that of an elastic beam subject to deformations imposed by the surrounding ground. Three types of deformations (Owen and Scholl, 1981) express the response of underground structures to seismic conditions (see Fig.)1) axial compression and extension2) longitudinal bending3) ovaling/racking

Deformation modes of tunnels due to seismic waves (after Owen and Scholl, 1981)

Geological structure prediction by seismic reflection method (called TSP method)Outline of the geological structure prediction by TSP methodSattelet al. (1992) proposed a technique, which carries out VSP exploration in the tunnel, and developed prospecting system called TSP202 including the data analysis software. This technique is called the TSP method, and it has been introduced in some construction companies in Japan. When TSP method is applied, the tunnel wall surface is equipped with exploration traverse line, which is parallel to the tunnel shaft. A receive point is set at 50m away from the tunnel face, and within this distance usually 24 shot points by explosion are set. Array measurement is carried out between the receiver and shot points. As an output in the TSP method may show the reflection event crossing position ahead of the tunnel face, the change of property of reflection plane can be judged from the change of the phase. The TSP method image is simple, but there is a little information on characteristic of geological structure such as the reflection event, so it becomes a difficult situation when the effect of the tunnel on quality and construction is being estimated. Experience of utilizing geophysical exploration in tunnel construction management is little, while the technique of utilizing exploration geological information ahead of tunnel face for construction management has not yet been established. In this paper, investigation characteristic of the TSP method was accumulated, and the utilization to the construction was tried. And a technique of utilizing geological information ahead of tunnel face for tunnel construction management was examined.

Geological structure evaluation by the TSP methodThe fundamental principle of the TSP method requires propagation velocity of elastic wave (P wave) and the distance to reflection plane from the time-of-arrival, and the position of the reflection plane is established by an array measurement. The reflection of an elastic wave in the underground is generated on the boundary surface of the media with different acoustic impedance based on the Snell law (1). This time, it is possible to show the energy of reflectedwave in the reflection coefficient (2).

Zi=piVi

zi: Acoustic impedance

ri= ------------------------

ri: The reflection coefficientIn case of ri<0, the reflected wave phase will reverse positive and negative, so the change of a medium acoustic impedance can be estimated from the phase change of reflected wave._ In case of zi+1>zi, phase of the reflected wave is coordinate._ In case of zi+1<zi, phase of the reflected wave is opposite.In case of high acoustic impedance (zi), it is necessary that the velocity of elastic wave (Vi) or the density _i (or both of them) should be high. Generally, when acoustic impedance increases, a change to the hard rock is assumed because both the density and the velocity of elastic wave in the hard rock are high. Therefore, it seems possible to estimate the change of the property in the reflection plane from the pattern of the phase change of reflected wave. Geological structure of 4 patterns, including fault, dyke and two kinds of rock type boundary are estimated from the reflection pattern as shown in Table .

CONCLUSIONSIn this paper, different ground investigation techniques that utilized geological information during and after a tunnel construction were examined. A flowchart was established as a guide for the execution of the investigation. Based on this flowchart initially the purpose of the investigation is set, then the research method is selected and the characteristic evaluation for the investigation is carried out. A case study about acquiring geological information by utilizing the TBM machine data as well as by using the TSP method (a kind of

Zi+1-Zi

Zi+1+Zi

elastic wave reflection method) was presented. It was found effective to utilize the information obtained by those methods in the construction of a tunnel.As the data were accumulated for appropriate evaluation of the characteristic of the ground investigation, a database was developed. By improving this database, it is considered possible to quickly and accurately utilize the geological information attained from the ground investigation of a tunnel construction.The geology along a tunnel alignment plays a dominant role in many of the major decisions that must be made in planning, designing, and constructing a tunnel. Geotechnical services, data collection, and evaluation should begin very early in the conceptual planning of any project and should continue through construction and even after construction to document the as-built conditions and the behavior of the tunnel in service.There is a fundamental difference between the ways geotechnical investigations are conducted for undergroundconstruction than for any other project. This is related to the fact that, in order to predict costs, the geotechnicalengineer must estimate the behavior of the tunnel under several anticipated excavation and lining scenarios. Thus, the investigative program must be directed toward the goal of predicting behavior and estimating costs.Geotechnical investigations should be carefully planned to take into account the significance of geology as well as the vast uncertainty associated with underground design and construction. There is wide latitude for determining what should be done during an investigation. Each project is unique; there is no fixed standard or check-off list that can be used to determine the scope and how to do geotechnical investigations. Past practices in the United States resulted in the cost of geotechnical investigations being on the order of one percent of the total cost of the tunnel.USNC/TT recommended that the cost of geotechnical investigations be increased to 3% of the total cost of the tunnel. However, some investigations, especially those involving hazardous waste have been as high as 8% or more in the case of nuclear waste. No matter what the final magnitude of cost, there is a need to fund more geotechnical investigative work at earlier stages of a project.

REFERENCES:1. http://www-civ.eng.cam.ac.uk/geotech_new/people/bolton/geotechnology.html 2. http://geology.com/articles/what-is-geology.shtml 3. Research paper on “PLANNING AND SITE INVESTIGATION IN TUNNELLING” by “Harvey W. Parker”4. Research paper on “Tunneling information - An oriented construction technique using geological

information” by“KAZUHIRO ONUMA, HIROYOSHI KASA, HIROYUKI YAMAMOTO and SHINJI UTSUKI”5. Research paper on “Tunnels under seismic loading: a review of damage case histories and

protection methods” by “ G. Lanzano+, E. Bilotta, G. Russo” Department of Hydraulic, Geotechnical and Environmental Engineering (DIGA).(University of Naples Federico II, Italy and+ SAVA Department, University of Molise, Campobasso, Italy ).

6. Research paper on “Effects of Seismicity on Rock Support in Tunnels of Different Sizes” by “ RajinderBhasin& Amir M. Kaynia” (Norwegian Geotechnical Institute), “D.K.Paul, Y. Singh and Shilpa Pal” (Department of Earthquake Engineering, IIT, Roorkee)

7. Research paper on “Engineering Survey System for TBM (Tunnel Boring Machine) Tunnel Construction” by “Andrew Hung Shing Lee, Hong Kong”

Serial no.

Contents Signature

1. Introduction of geology and geotechnology

Difinition of geology

Geotechnology in contruction of tunnelling

History of geology

2. Role of geotechnology in planning

3. When to conduct geotechnical investigations

4. Tunnelling geological information evaluation techniqueFlow chart

Case study

5. Case study of tunnelling information

The outline of the case study of tunnelling informationUtilization of geotechnology information of geological information based on TBM machine dataGeoloical structure prediction by seismic reflection TBM

6. Tunnels under seismic loading

Crack distribution along tunnel lining

Conclusion

references