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Tunnel sectionsTunnels range in dimensions of cross-sections from those of small galleries driven by miners working with hand tools, to tunnels large enough to accommodate railroad trains, double lane of highway traffic, or to transport very large volume of water as in diversion structures in dams. A minimum size of tunnel is 9 ft high and 4 ft wide at the working face. Designed shapes or sizes of tunnels in x-section conform to a planned uses to tunnel and some extent to the nature of the material that is anticipated will be encountered during excavation, x-sectional shapes vary from square or rectangular as for example in mining operations in strongly bedded sediment rocks, to circular. A common type of x-section is horseshoe shaped to provide maximum stability in the roof portion of the tunnel. Geological explorationThe geological conditions that are likely to meet in any given work of construction must be predicted. The line of the tunnel and the neighboring ground is geologically surveyed and sub-surface data obtained by exploratory boring. Careful control of such trial boring operations is necessary in order to extract the maximum amount of information from the ground. The cost of tunneling in general is least where construction is carried out in sound rock, and in one kind of rock throughout. Straight forward geological conditions such as simply dipping strata allow cost to be estimate easily; more uncertainties arise in connection with folded and faulted beds. Geological structures such as faults and joints should be mapped along the line of a tunnel. Strongly developed joints systems are potential channels for underground circulation and should be recorded. Badly fractured ground is to be avoided if possible. If unavoidable it may require special timbering or other treatment, and a prediction of where faults are likely to meet underground is therefore of greater importance. Hard rocks where excavated may stand with little support (some tunnels are unlined throughout) because they are strong enough to withstand the lateral pressure exerted by surrounding rocks but if soft bands are present there may be a tendency to slipping on these weaker layers and suitable support for the walls of the excavation will be necessary. Inter- bedded hard and soft rocks, such as sand-stones and shales may give rise to many difficulties. Ground-water percolating through the sand-stones soaks into the shales and softens them and hence the slipping is promoted.

Rock support for tunnels and underground cavern design is a demanding and very complex task. In principle, the problem can be approached from two directions: The first way is to define the relationship between geo-mechanical properties of the rock mass and the support methods used. This is mostly based on the utilization of statistical and empirical data gathered in similar conditions. The second way is to estimate the deformation characteristics of the rock structure, and then the related effect on supporting structures. This method typically requires very good rock property and rock mass property data. The most important factors affecting rock reinforcement method and design are: Geological factors, such as rock mass structure. Dimensions and geometry of excavated space. Location and direction of caverns in the rock mass. Excavation method. Use and expected lifetime of space. Common support methods in underground construction work are: Bolting. Sprayed Concrete. Steel Arches. Concrete Lining. Grouting. 1. BOLTINGRock bolting is one of the most common methods of rock reinforcement. The main principle of bolting is to reinforce loose rock or fractured in-situ rock to precent caving or spalling, and to assist the rock mass to form its own self-supporting structure. Bolts can be divided into three categories according to the way they behave in the rock, for example, grouted bolts, mechanically anchored bolts and friction bolts. 1.1. Cement-grouted boltsCement-grouted rebar is still the most inexpensive and widely used rock bolt, because it is simple and quick to install and can be used with or without mechanized equipment. Correctly installed, a cement-grouted bolt gives rock support for years. The grout cement provides protection from corrosion. Special galvanized and/or epoxy coated bolts can be used in extremely severe conditions. The major disadvantages of the cement-grouted bolt is its relatively long hardening period. The grout takes between 15-25 hours to harden; therefore, it does not provide immediate support. When immediate support and/or pre-tensioning is needed, a grouted wedge-type or expansion-shell bolt can be used. Mixing additives in the grout can reduce the hardening time, but it also increases bolting cost. The water/cement ratio considerably affects the quality of installed bolts. The best water/cement ratio is 0.3 (w/c). This grout density can be easily used and maintained when using mechanized bolting equipment. 1.2. Resin-grouted boltsResin-grouted bolts give the required support relatively quick due to a short hardening time. When correctly installed with full-length grouting, the resin-grouted bolt is considered to give permanent support with a life span of 20 to 30 years. By using resins with two different hardening times, with faster one at the bottom of the hole and another that is slower at the stem, the bolts can be pre-tensioned. The same can be done for short-time support by only bottom-grouting the bolt. 1.3. Cable boltsCable or steel strained bolts are used to bind and secure large volumes of rock around large caverns. Cable bolts can be used both before and after excavation, and also used for preventing rockslides in mountain slopes and quarries. The anchor itself is a steel strand, typically two strands of 15.2 mm in diameter, with typical bolt length being between 10-25 meters. Today, with mechanizes equipment, the installation and grouting of cable bolts of any length is fast and efficient, and the cable bolt's bearing capacity clearly exceeds capacity of rebar steel bolts. Its lack of efficient protection against corrosion limits its extensive use in permanent rock support. 1.4. Mechanically anchored boltsMechanically anchored bolts are usually wedge or expansion-shell bolts that are point-anchored at the bottom of the hole. The bolt has an expanding anchor at its end. After insertion, the bolt is either rotated or pressed/hammered against the bottom of the hole. This expands the wedged end and anchors the bolt firmly to the end sides of the hole. To install anchored bolts successfully, the hole size must be accurate, and the rock must be relatively solid. Wedge or expansion-shell bolts are typically meant for temporary rock support. Together with cement grouting, it provides both immediate and long-term support. 1.5. Friction-type boltsTypical examples of friction-type bolts are the split-set and Swellex bolts. Both are quick and easy to install and give instantaneous support. They cannot, however, be used for long-term reinforcement. The split-set bolts is hammered into the hole, which has a slightly smaller diameter than bolt. Using the correct hole size for a specific bolt diameter is essential for successful installation. Split set bolts are very suitable for layered formations. The Split-set bolts provide immediate support but only for fairly short period of time. A disadvantage is that the split-set cannot be effectively protected against corrosion. The life span can somewhat be extended by using cement grouting. The Swellex bolt has a longer life span than the Split-set. It is installed by applying high-pressure water to bolt after inserting it to the hole. The high pressure expands the bolt to its final dimensions in the hole, therefore enabling it to utilize the roughness and fractures in the bolt hole surface. As with the Split-set bolt, poor corrosion protection limits this bolt. 1.6. Equipment for bolt installationDevelopment of mechanized equipment began as early as the 1970s. Today there is a wide selection of fully mechanized equipment, and a wide variety of different methods for bolt installation. The main factors affecting the choice of method are usually tunnel size, number of bolts to be installed and work cycle arrangement at this site. Manual operation, the hand-held drilling and installation of bolts, is typically used in small drifts and tunnels where drilling is also performed by hand-held equipment, and there is a limited amount of bolting work. Semi-mechanized installation is still typical at tunneling work sites. The drilling jumbo is used for drilling bolt holes, and bolt installation is performed from the jumbo's basket boom or from a separate utility carrier or truck. With today's full mechanized equipment, one operator can handle the entire bolting process from drilling to grouting and bolt installation. The operator is positioned away from the unbolted area under a safety canopy that protects him from failing rock. Although safety is a major reason for the development of mechanized bolting equipment, the superior installation technique of mechanized bolting rigs also produces consistently higher bolting quality. Thanks to powerful cement mixers, pumps and effective grouting methods, the bolts are securely fixed and grouted to their full length, providing a sound reinforcement structure, even with long bolts. 2. SCREENINGScreening, which is the installation of wire mesh, is most typically used in underground mining, but also construction sites together with bolting and/or sprayed concrete. Screening is primarily performed manually by applying the wire mesh together with bolting of the tunnel. It can also be done by mechanized equipment, such as by having a screen manipulator on the bolting or shotcreting unit, or on a dedicated screening machine. 3. SPRAYED CONCRETESprayed concrete, otherwise called shotcreting, is widely used support method in construction. It is used for temporary or long-term support, lining and backfilling. Usually, shotcrete is used together with bolting to obtain the best support or reinforcement. Shotcrete can be reinforced by adding steel fiber to the concrete. The most common forms of shotcreting are dry-mix and wet-mix methods. In the dry-mix method the aggregate, cement and accelerators are mixed together and propelled by compressed air. Water is added last through a control valve on spray nozzle. The dry method is suitable for manual shotcreting because the required equipment is usually inexpensive and small. On the other hand, dry method can pose a health hazards as it creates considerably more dust and rebound than the wet method. The quality also depends heavily on the shotcreting crew and may vary widely. In the wet mix method, aggregate, cement, additives and water are measured and mixed before transport. Today, wet mix is more widely used because it is easy to mechanize and the capacity can easily out-do the dry method. Rebound rate is low and the quality procedure is even. Critical factors in shotcreting are: Water/cement ratio. Grain size distribution of aggregate. Rebound ratio. Grain size distribution. Mix design. Nozzle design. Nozzle distance and angle. Layer thickness. Manual shotcreting has been largely replaced by mechanized shotcreting machines. With mechanized equipment, multiple capacities per hour can be reached, together with consistent and even quality of the concrete layer. Safety, ergonomic and environmental conditions are other important aspects of shotcreting. These factors are efficiently improved with mechanized shotcreting units. 4. STEEL ARCHESSteel arches are common permanent support method for weak rock formations. These are usually installed in the tunnel immediately after each round, at the same time as rock bolting. Steel arches are also commonly installed during shotcreting to give temporary support before final concrete lining of e.g. traffic tunnels. 5. GROUTINGGrouting is the method in which a solidifying liquid is pressure-injected into the rock mass. The main purpose of grouting is to prevent ground water leakage into the tunnel, and to increase overall rock mass strength. In grouting, a chemical agent or cement mass is pressure-pumped into the drill-hole to penetrate fractured and fill cavities. In drill and blast tunneling, grouting is typically performed before (pre-grouting) or after (post-grouting) excavation. 5.1 Pre-groutingPre-grouting means that rock mass is grouted before excavation begins. Usually, pre-grouting is done from the tunnel, but in situations with low overburden it is also possible to do it from the surface. Probe holes are drilled to map possible fractures and register water flow. This helps to analyze the need for grouting. Later, grout holes are drilled in conical-fan shape in front of the tunnel face. Typical grouting fan length is 15-25 meters. After drilling, the grouting agent is pumped into the hole until leakage has reached an acceptable level. Tunnel excavation can begin once the grouting mass has settled. Grouting fans overlap each other so that in 15-meter-long grout holes, grouting is performed every second or every third round depending on the round length. 5.2 Grouting after excavation (post-grouting)When grouting is done after excavation, grouting holes are drilled from the tunnel in a radial form. In good rock conditions with small water leakage, post-grouting is often adequate. Post-grouting enables better rock mass structure evaluation. On the other hand, water leakage blockage is more difficult because the water flow tends to flush away the grouting agent before it hardens. 5.3. Grouting agentsThe grouting agents can be divided into two categories: Suspension and Chemical. Cement water or bentonite water suspension is the most typical in rock grouting because both are cost-effective and environmentally safe. The drawback is, however, a relatively large maximum grain size, which leads to poor penetration in small cracks. Penetration characteristics can, however, be improved by adding additives. Silicate-based chemicals are also used to speed up the hardening time. Chemical agents are silicate-based, resin polymers, polyurethane-based or lignin-based chemicals that typically penetrate very s cracks and have adjustable hardening times.

Angle measurementFor angle measurement with theodolite vertical hair is used. Basically, there are two methods horizontal angle measurement, Repetition method (For single angle) Reiteration method (For more than one angle) 1. By Repetition methodLet suppose it is desire to measure the angle A from the following figure. We will use repetition method for this purpose. ProcedureSetup the theodolite at station A. Bisect the point B with vertical hair of theodolite and move telescope in clockwise and direction to bisect at point C. Note this circle reading in the book and fix this circle reading, then again bisect the point B by keeping the circle reading fixed. Now, release the circle reading and rotate the telescope again in clockwise direction till it bisect again point C. Similarly get 3rd and 4th repetition and note the circle reading after 4th repetition in the book. Change the face of telescope and repeat the above steps, an example and method of booking observations have given below, Inst. Station Angle Face Repetition Circle Reading (° ′ ″) Angle value (° ′ ″) Mean of faces (° ′ ″) A BAC L 1 25 20 00 25 20 10 25 20 9.5 4 101 20 40 R 1 25 20 03 25 20 09 4 101 20 36 2. By Reiteration methodThis method is used if there are more than one angles to be measure from a certain station point. Consider the following figure, we will measure angles AOB and BOC using this method. ProcedureSetup the theodolite at station O, bisect the point A with a certain circle reading with face left. Rotate the instrument in clockwise direction and bisect B, note the circle reading. Then rotate and the telescope till it bisect the point C, note this circle reading also. All these reading will book into face left position. Transit the telescope and rotate the instrument through 180°, this time bisect the point C firstly and then rotate telescope in anticlockwise direction towards B and then ultimately towards A. Put these readings in face right position. You can do more than one sets of measurements for the accurate results, I have done one set and booking method is as follows, Inst. Station Stn. Sighted Face Circle reading (° ′ ″) Mean of faces (′ ″) Angle value (° ′ ″) O A L 10 20 05 20 06 AOB 37 10 05 R 190 20 07 B L 47 30 10 30 11 R 227 30 12 BOC 41 10 14 C L 88 40 20 40 25 R 268 40 30 One should start observation with some initial circle reading say 25°, if we start our observation with zero circle reading our calculations for computing mean will be little bit difficult.

TraversingIt is the method of establishing horizontal controls. TraverseTraverse is a series of connected lines forming or not forming a loop. In the first case it is called closed traverse (when the loop is formed) and in the second case it called open traverse (when loop is not formed). Vertical controlThat is the reference point in vertical plane, it includes series of benchmarks and points of known elevations. Horizontal controlIt is the series of points in the horizontal plane of known co-ordinates. Types of traversingTraversing can be further divided into two categories depending upon the type of instrument used, Compass Traversing Theodolite Traversing 1. Compass traversingWhen prismatic compass is used for determining the direction of line, the method is called compass traversing. 2. Theodolite traversingWhen theodolite is used for measurement of angles or directions, the method is called theodolite traversing. By direction of line, we mean the bearing of that line.

MeridiansMeridian is a reference direction with respect to which the direction of lines is mentioned. There are three types of meridians - True Meridian, Magnetic Meridian & Arbitrary Meridian 1. True MeridianIt is the reference direction of north pole of earth from a given station point. It is also called geographic meridian. 2. Magnetic MeridianIt is the direction of north pole indicated by magnetic needle. 3. Arbitrary MeridianThis is any assume direction to a well-defined object. It may be useful for small areas. e.g. A mosque is taken as reference and location of road will be mentioned with respect to this mosque. Direction of magnetic north with respect to true north is called magnetic direction. BearingsBearing is the angle which a certain line makes with a certain a certain meridian. Bearing with respect to true meridian is called true bearings while magnetic bearing is the angle which a line makes with respect to magnetic meridian. There are two ways to represent the bearings, Whole circle bearing (W.C.B) Reduced Bearing (R.B) 1. Whole Circle Bearing (W.C.B)It can be taken 0° to 360°. Quadrants are taken clock-wisely and angles are also determined in clockwise direction. 2. Reduced BearingReduced bearing or Quadrantal bearing is the angle which a line makes from North or South Pole whichever may be near. It is value is from 0° to 90°. Using the above figures, you can easily convert the Whole Circle Bearing into Reduced Bearing. Some Examples are given are below. Whole Circle Bearing (W.C.B) Reduced Bearing (R.B) 135° S45E 37° N37E 65° N65E 125° S55E 215° S35W 300° N60W

1. Using rise and fall methodIn this method booking is done in the following manner, B.S I.S F.S Rise Fall R.L Remarks 2.570 - - - - 100.00 A 3.750 - 1.200 1.370 - 101.37 C.P - - 3.750 - 0.70 100.67 B 5.620 - 4.950 1.370 0.70 - - 1) On any page of book, the first reading is always a B.S and last reading is always a F.S. If you are not getting F.S as last reading on each page, then it means you have done mistake while booking readings. 2) From the B.S next F.S is subtracted. If the answer is positive (+), it will be Rise and if the answer is negative (-) it be Fall and put that reading in respective box. 3) In the above table, I have assumed that Reduce Level (R.L) of point A is 100.0 and you can see R.L of point B is 100.67, which shows that point B is .67 units higher than point A. In case of numerous readings, the check should be applied at the end of each page while booking reading, ∑ (B.S) - ∑ (F.S) = ∑ Rise - ∑ Fall = R.L of last point - R.L of first point; 5.620 - 4.950 = 1.37 - 0.70 = 100.67 - 100.00 = 0.67 = 0.67 2. Using height of collimation method (H.O.C)For this method use the following formulas, R.L + B.S = H.O.C and H.O.C - F.S = R.L B.S I.S F.S H.O.C R.L Remarks 2.50 - - 102.50 100.00 - 1.75 1 1.95 102.30 100.55 - - 2.55 - - 99.75 - - 2.70 - - 99.60 - 2.95 - 3.10 - 99.20 - - - 2.75 - 99.40 - 7.20 - 7.80 - - - All other considerations are same as Rise/ Fall method. Below check have applied, ∑ (B.S) - ∑ (F.S) = R.L of last point - R.L of first point = 7.2 - 7.8 = 99.4 - 100 = -0.6 = -0.6

Types of sewers1. Sanitary sewerIt carries sanitary sewage i.e. wastewater from municipality including domestic and industrial wastewater. 2. Storm sewerIt carries storm sewage including surface runoff and street wash. 3. Combined sewerIt carries domestic, industrial and storm sewage. 4. House sewerIt is the sewer conveying sewage from plumbing system of a building to common/municipal sewer. 5. Lateral sewerThis sewer carries discharge from house sewers. 6. Submain sewerThis sewer receives discharge from two or more laterals. 7. Main or trunk sewerIt receives discharge from two or more submains. 8. Outfall sewerIt receives discharge from all collecting system and conveys it to point of final disposal. Types of sewer systems1. Separate systemIf stormwater is carried separately from domestic and industrial wastewater, the system is called separate system. Separate systems are favored when: There is an immediate need for collection of sanitary sewage but not for stormwater. When sanitary sewage needs treatment, but the stormwater does not. 2. Combined systemIt is the system in which the sewer carries both sanitary and stormwater. Combined system is favored when: Combined sewage can be disposed off without treatment. Both sanitary and stormwater need treatment. Streets are narrow and two separate sewers cannot be laid. 3. Partially combined systemIf some portion of storm or surface runoff is allowed to be carried along with sanitary sewage, the system is known as partially combined system. In urban areas of developing countries, mostly partially combined system is employed.

History of electronic distance measurementIn surveying distance measurements were always a challenge for surveyors specially when long distances were to be measured with high accuracy. In 1950 scientist tried to calculate the distance by using light beam to travel over unknown distance with measured time. Ordinary lights travel at a velocity of 186,000 miles per second, therefore the time taken will be very small to cover a short distance. This idea was soon dropped but the scientists succeeded in finding a low velocity light beam in form of Infra-Red Rays generated by solid state Gallium Arsenide Diode (GAD). This was put into laboratory experimentation in 1960 and finally instrument called Electronic Distance Measurement came into existence. Initially the instruments were very expensive but as the demand increased the price was within the reach of most professionals. Revolution in surveying due to EDMModern EDM equipment contains hard-wired algorithms for reducing the slope distance to its horizontal and vertical equivalent. For most engineering surveys, Total stations combined with electronic data loggers are now virtually standard equipment on site. Basic theodolites can be transformed into total stations by add-on, top-mounted EDM modules. The development of EDM has produced fundamental changes in surveying procedures e.g. Traversing on a grandiose scale, with much greater control of swing errors, is now a standard procedure. The inclusion of many more measured distances into triangulation, rendering classical triangulation obsolete. This results in much greater control of scale error. Setting out and photogrammetric control, over large areas, by polar coordinates from a single base line. Deformation monitoring to sub-millimeter accuracies using high-precision EDM The latest developments in EDM equipment provide plug-in recording modules, capable of recording many thousand blocks of data for direct transfer to the computer. There is practically no surveying operation which does not utilize the speed, economy, accuracy and reliability of modern EDM equipment. For example, the EDM instrument Model # LEICA RM100 BUILDER POWER have the following particulars, Absolute circle reading Laser plummet Endless drives 30x magnification Dual-Axis compensation High resolution LCD display Electronic laser distance measurement Graphic sketches EDM measurement with red laser on target Upload and transfer data Data editing and exchange Connectivity to 3rd party devices Hence, the advent of EDM equipment has completely revolutionized all surveying procedures, resulting in a change of emphasis and techniques. Taping distance, with all its associated problems, has been rendered obsolete for all base-line measurement. Distance can now be measured easily, quickly and with great accuracy, regardless of terrain conditions.