Tunnel Forepoling defines the placement of near-horizontal steel bars/ pipes/ section around the periphery of the heading to form a rock support cage. in areas of the weak zone. In other words, To support the excavation roof or Tunnel crown. Forepoling shall be applied to rock and soil conditions which tend to produce overbreak, collapses or material inflow immediately after excavation. It shall be applied locally or systematically, as the circumstances require for the safety of the works and for preventing overbreak.
These are made of metallic, non-metallic and/or composite materials. It is primarily applied to arrest and catch rocks, boulders, shooting stones or debris that can be flowing or falling due to natural causes. The rockfall protection barrier is a support solution allowing to hold these disintegrating and falling elements, subsequently avoiding damages to infrastructure and preventing disruptions such as traffic blockages. It has an ability to withstand energy impacts typically up to 5000KJ.
MTBM- Micro Tunneling Boring Method
Micro tunneling is a trenchless construction method in which a borehole is excavated and pipes laid simultaneously using remote guidance, pipe jacking, and continuous support. The micro tunneling boring machine (MTBM) is operated from a control panel, normally located on the surface. Personnel entry is not required for routine operations. Water jetting is used for the cutting head during the boring stage, or an asymmetrical or slanted head and is directed using laser guidance. Only pipes with a circular cross-section can be used because of the boring process. Microtunneling has successfully completed horizontal as well as vertical curves. Horizontal curves allow pipeline projects to follow curved public rights-of-way without too many manholes, and short straight segments. t is effective in soft, unstable, and wet soils and can crush large boulders.
This test method covers procedures for testing vertical and batter piles either individually or in groups to determine the load-deflection relationship when subjected to lateral loading. It is applicable to all deep foundation units regardless of their size or method of installation. Load Test shall be performed when concrete has reached its required strength i.e. 28 days strength. The Pile head to be
chipped off upto 300mm above Cut-off- Level. The test to be conducted at cut-off level. During the load test, records including plots of load vs. time and load vs. settlement will be maintained progressively.
Pile Head Treatment
Piles were cast with high slump concrete, during the concreting of piles, there is a chance that fines from concrete might accumulate at the top and also if there is any slush in the bored pile, it will also come up during concreting. So the concreting of the pile is overflowed to take out all impurities. After casting of the piles, the top portion of the pile is chipped out till the pile cap. Excavation is done around the pile area to facilitate removal of the extra pile portion by chipping. Pile Chipping is the extra pile that is above the cutoff level, which provided for good and sound concrete. The main purpose of chipping is to remove the surplus slushy concrete (a mixture of concrete, slurry, and mud) over the cutoff level. When concreting is going on, the black slush comes out from the borehole. Black slush represents the mud which produced at the time of boring.
Manufactured sand from crushing aggregates
Sand is world’s second most consumed natural resource after water. Rapid urbanization and global population growth have created unbound demand for this limited natural resource. With urbanization as key driving factor, construction industry has expanded considerably over the last few decades leading to overuse of river sand for construction purposes. This increasing discrepancy between the need for aggregates in the society and scarcity of natural sand due to exhaustion of resources and environmental considerations, has urged concrete manufacturers to look for a suitable and sustainable alternative fine aggregate. The economical and ecological alternative is Manufactured sand. Manufactured sand (M-Sand) is artificial sand produced from crushing hard stones into small sand sized angular shaped particles, washed and finely graded to be used as construction aggregate. It is a superior alternative to River Sand for construction purpose.
Secant Pile Installation using segmental casing
Secant Piled Wall is a retaining wall constructed for ground retention prior to excavation. The wall is formed by constructing alternating primary (female) and secondary (male) piles where the secondary piles partially cut into either side of the primary piles in order to form a continuous impervious structure. Secant walls are frequently used to as an alternative to Diaphragm walls where obstructions are anticipated, or in urban basement projects where space is limited. In comparison to diaphragm walls they can be flexible in shape and offer a relatively compact operation in comparison to the equipment required to support bentonite holding and circulation equipment.
Soil nailing is a ground stabilisation technique that can be used on either natural or excavated slopes. It involves drilling holes for steel bars to be inserted into a slope face which are then grouted in place. Mesh is attached to the bar ends to hold the slope face in position. The main considerations for deciding whether soil nailing will be appropriate include; the ground conditions, the suitability of other systems, such as ground anchors, geosynthetic materials, and so on and cost.
Although soil nails are versatile and can be used for a variety of soil types and conditions, it is preferable that the soil should be capable of standing – without supports – to a height of 1-2 m for no less than 2 days when cut vertical or near-vertical. Soils which are particularly suited to soil nailing include clays, clayey silts, silty clays, sandy clays, glacial soils, sandy silts, sand, gravels. Soil nailing can be used on weathered rock as long as the weathering is even (i.e. without any weakness planes) throughout the rock. Soils which are not well-suited to soil nailing include those with a high groundwater table, cohesion-less soils, soft fine-grained soils, highly-corrosive soils, loess, loose granular soils, and ground exposed to repeated freeze-thaw action.
Hose Reel Sprinkler Irrigation
Hose reels also called as Traveling Gun Systems or Raingun on wheels. These systems are usually hard hose reels with a sprinkler/rain gun attached to a cart at the end of the hose. They consist of a water gun that sprays water over the crops as the sprinkler cart progresses along an irrigation path. These systems follow the path where the hard poly hose has been laid, rolling it up as it travels. They require much less labour than movable Raingun systems. It has Speed control to ensure right quantity and Precise of application of water. Also Can be operated in fields where there is no power supply. Ideal for close row crops like wheat, cotton, chickpeas, bajra, potatoes, soybeans, groundnuts, maize, oil seeds and pulses
Rock Anchoring work
Rock anchoring uses metal bars called rock anchors. These are drilled directly into the stable rock, flushing out debris in the process. Due to the anchors being located at the centre of the rock mass, the natural stability of the land is transferred to the exterior surface, preventing movement and collapse. The rock anchors are then secured to each other by a mesh, which is mounted to the surface. Alternatively, spade or sock anchors can be used. Spade anchors consist of an anchor head attached to a flexible steel tendon. The head is secured into the ground and the tendon stressed, causing the head to rotate 90 degrees and lock itself firmly into place. Meanwhile, sock anchors are a steel bar inside a fabric sock, which is pumped full of grout. This is ideal for areas of rock that contain fissures, as the sock shapes itself into the gaps and hardens, effectively filling the empty pockets.
If the depth of footing greater or equal to the Width of footing, it is known as the deep Foundation. Deep Foundation is used Where the bearing capacity of the soil is very low. The load coming from the superstructure is further transmitted vertically to the soil. A deep foundation is a type of foundation which is placed at a greater depth below the ground surface and transfers structure loads to the earth at depth. The depth to width ratio of such a foundation is usually greater than 4 to 5. The construction process of a deep foundation is more complex and more expensive than shallow foundations. However, when dealing with poor soil conditions at shallow depth, large design loads, and site constraints, a deep foundation is likely to be the optimum solution.
Mega tunnel boring machines
As urban areas become denser, open space for new infrastructure is less available and more and more clients are looking underground as they envision projects involving transportation infrastructure, utilities, water, wastewater, power and other systems. As a result, the number of tunnels under construction will continue to grow as city, county and state planners recognize the value of subsurface structures in addressing surface space constraints. Unfortunately, many of the “easy” places to build tunnels have been used over the past 100 years and those locations previously dismissed as too challenging are being reconsidered. The good news is that tunneling and tunnel boring technology has advanced to allow construction of tunnels in locations and in geology that engineers would not have thought possible just a decade ago. In addition to being able to tunnel in more difficult ground, the size of tunnel-boring machines is getting bigger and their control systems becoming more sophisticated, allowing them to reduce surface impacts due to settlement and excavate tunnels with higher groundwater pressure than previously possible.
Construction of Largest & Longest Arch bridge
The foundation of any structure is the most important component of that structure. This is the component of the structure were all forces are transferred to before entering into the ground. If the foundation fails the structure fails. The arch bridge carries loads primarily by compression, which exerts on the foundation both vertical and horizontal forces. Arch foundations must therefore prevent both vertical settling and horizontal sliding. In spite of the more complicated foundation design, the structure itself normally requires less material than a beam bridge of the same span.
Pressures Associated with Dams and Reservoirs
Construction of a dam and filling of the reservoir behind it create load stresses on the floor and sides of a valley that did not exist previously. The kinds and distributions of imposed stresses created by a dam on its foundation depend on the shape of the dam and the materials used in its construction. Dams built of masonry or concrete can be considered to behave as cohesive, rigid, monolithic structures. The stresses acting on the foundation is a function of the gross weight of the dam as distributed over the total area of the foundation on which the dam rests. Earth and rock fill dams exhibit gross semiplastic behaviour, and the pressure on the foundation at any point depends on the thickness of the dam above the point. The pressures exerted by earth and rock-fill dams resemble in some respects those exerted by the water in a reservoir, but pressure distribution is modified by the fact that the materials of construction have some inherent strength, and fail only after some threshold stress has been exceeded. Pressures exerted by water in the reservoir behind a dam are hydrostatic and increase linearly with depth. The pressures are hydrostatic and increase with depth. On the assumption that the pressures are directed normal to the floor and sides, they are shown as vectors of increasing magnitude with depth
Prefabricated Vertical Drains Installation
Prefabricated Vertical Drains (PVDs) or ‘Wick Drains’ are composed of a plastic core encased by a geotextile for the purpose of expediting consolidation of slow draining soils. They are typically coupled with surcharging to expedite preconstruction soil consolidation. Surcharging means to pre-load soft soils by applying a temporary load to the ground that exerts stress of usually equivalent or greater magnitude than the anticipated design stresses. The surcharge will increase pore water pressures initially, but with time the water will drain away and the soil voids will compress. These prefabricated wick drains are used to shorten pore water travel distance, reducing the preloading time. The intent is to accelerate primary settlement. Pore water will flow laterally to the nearest drain, as opposed to vertical flow to an underlying or overlying drainage layer.
Vibroflotation- Sand Columns Installation
Vibroflotation also known as vibrocompaction utilizes horizontal vibrations in conjunction with fluid to reduce the interparticle friction of the surrounding soil. This allows the material to densify and creates a column with improved engineering characteristics, including an increase in strength and a reduction in compressibility. The technique of sand or stone columns is widely used to improve the load carrying capacity and reduce thesettlement of soft soils. The technique consists of excavating holes of specific dimensions and arrangement in the soft soil and backfilling them with either stone or sand particles. Vibro-compaction is not effective where the fines (silt and clay) exceeds 20 per cent. Coarser grain size limit is applicable to vibro-compaction.
Cannot be used in low permeable soils.
Shotcrete, also called (trademark) Gunite, concrete applied by spraying. Shotcrete is a mixture of aggregate and portland cement, conveyed by compressed air to the nozzle of a spray gun, where water is added. The wet mixture is then sprayed in place and may be carved or troweled almost immediately. Shotcrete is used to reinforce both temporary and permanent excavations. It may be employed, in concert with lagging and other forms of earth anchor, to stabilize an excavation for an underground parking structure or hi-rise during construction.
Water Hammer Method
Water hammer is a phenomenon that can occur in any piping system where valves are used to control the flow of liquids or steam. Water hammer is the result of a pressure surge, or high-pressure shockwave that propagates through a piping system when a fluid in motion is forced to change direction or stop abruptly. This shockwave is also commonly referred to as a hydraulic shock or hydraulic surge, and may be characterized by a marked banging or knocking sound on the pipes immediately after shutoff. Water hammer can occur when an open valve suddenly closes, causing the water to slam into it, or when a pump suddenly shuts down and the flow reverses direction back to the pump. Since water is incompressible, the impact of the water results in a shock wave that propagates at the speed of sound between the valve and the next elbow in the piping system or within the column of water after the pump.
Sheet Pile Installation
Sheet piles are sections of sheet materials with interlocking edges that are driven into the ground to provide earth retention and excavation support. Sheet piles are most commonly made of steel, but can also be formed of timber or reinforced concrete. Sheet piles are commonly used for retaining walls, land reclamation, underground structures such as car parks and basements, in marine locations for riverbank protection, seawalls, cofferdams, and so on.
Dowel Bar in Rigid Pavement
Dowel bars are short steel bars that provide a mechanical connection between slabs without restricting horizontal joint movement. They increase load transfer efficiency by allowing the leave slab to assume some of the load before the load is actually over it. This reduces joint deflection and stress in the approach and leave slabs. Dowel bars are typically 32 to 38 mm (1.25 to 1.5 inches) in diameter, 460 mm (18 inches) long and spaced 305 mm (12 inches) apart.. In order to prevent corrosion, dowel bars are either coated with stainless steel (Figure 2) or epoxy (Figure 3). Dowel bars are usually inserted at mid-slab depth and coated with a bond-breaking substance to prevent bonding to the PCC. Thus, the dowels help transfer load but allow adjacent slabs to expand and contract independent of one another. Figure 3 shows typical dowel bar locations at a transverse construction joint.
Rock bolt, in tunneling and underground mining, steel rod inserted in a hole drilled into the roof or walls of a rock formation to provide support to the roof or sides of the cavity. Rock bolt reinforcement can be used in any excavation geometry, is simple and quick to apply, and is relatively inexpensive. The installation can be fully mechanized. The length of the bolts and their spacing can be varied, depending on the reinforcement requirements.
H-Beam Pile Installation
These structural beams are used extensively for deep foundation applications to add stiffness and support to sheet pile walls and foundations. H-Piles are steel beams that are driven into the earth by pile driving equipment. The tough and durable cross sections provide excellent driving characteristics when driving in difficult soil and rock conditions. Steel H-Piles are structural square beams that are available in a wide variety of sizes and can also be used for marine structure applications.
Shotcrete is a mortar or high performance concrete conveyed through a hose and pneumatically projected at high velocity onto a backing surface. It is the force of this spraying action that leads to compaction of the concrete or mortar which then forms layers of concrete to the required thickness . Shotcreting has proved to be the best method for construction of curved surfaces. Tunnel linings and domes are now much easier to construct with the advent of with shotcrete technology. Shotcrete is a widely accepted and used way of placing material that is cementitious in nature for a vast variety of applications.
Pull Out Test
The fundamental principle behind pull out testing is that the test equipment designed to a specific geometry will produce results (pull-out forces) that closely correlate to the compressive strength of concrete. This correlation is achieved by measuring the force required to pull a steel disc or ring, embedded in fresh concrete, against a circular counter pressure placed on the concrete surface concentric with the disc/ring.
The california bearing ratio test is penetration test meant for the evaluation of subgrade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement. CBR is the ratio expressed in percentage of force per unit area required to penetrate a soil mass with a standard circular plunger of 50 mm diameter at the rate of 1.25 mm/min to that required for corresponding penetration in a standard material. The ratio is usually determined for penetration of 2.5 and 5 mm . When the ratio at 5 mm is consistently higher than that at 2.5 mm, the ratio at 5 mm is used.
The Underwater concreting using tremie method is convenient for pouring large amount of high flowable concrete. The concrete is moved to the hopper by either pumping, belt conveyer or skips. Tremie pipe, which upper end connected to a hopper and lower end continuously submerged in fresh concrete, is used to place concrete at the exact location from a hopper at the surface. The reason to immerse the tremie pipe lower end is to prevent intermixing of both concrete and water.
Standard Proctor Test
Standard Proctor Test is used to determine the compaction of different types of soil and the properties of soil with a change in moisture content The Compaction test of soil is carried out using Proctor’s test to understand compaction characteristics of different soils with change in moisture content. Compaction of soil is the optimal moisture content at which a given soil type becomes most dense and achieve its maximum dry density by removal of air voids.
A prismatic compass is a navigation and surveying instrument which is extensively used to find out the bearing of the traversing and included angles between them, waypoints (an endpoint of the lcourse) and direction. Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and the length of the surveying lines are measured with a tape or chain or laser range finder. The compass is generally used to run a traverse line. The compass calculates bearings of lines with respect to magnetic needle. The included angles can then be calculated using suitable formulas in case of clockwise and anti-clockwise traverse respectively. For each survey line in the traverse, surveyors take two bearings that is fore bearing and back bearing which should exactly differ by 180° if local attraction is negligible. The name Prismatic compass is given to it because it essentially consists of a prism which is used for taking observations more accurately.
Post Tensioning of Slab
A Post tension slab is a combination of conventional slab reinforcement and additional protruding high-strength steel tendons, which are consequently subjected to tension after the concrete has set. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any column-free spaces. When these post tensioned steel tendons are stressed, the concrete is squeezed, in other terms, the concrete is compacted which increases the compressive strength of the concrete and at the same time the steel tendons that are pulled increase the tensile strength. As a result, the overall strength of the concrete increases.
Core Cutter Method
A Density is a measure of the strength of the soil. It is useful in estimating bearing capacity of soils, settlement of footings, earth pressure behind the retaining walls and embankments. The field compaction is controlled by the density. The relative density of cohesionless soils is determined by knowing the dry density of soils in its natural, loosest and densest states. The determination of voids ratio, porosity, and degree of saturation need the help of the density of soils.The core cutter method is a method used to determine the dry density of soil and 130 mm long and 100mm diameter cylindrical core cutters are used for testing the in-situ compaction of cohesive and clay soils.
Ultrasonic Pulse Velocity Test
The method consists of measuring the time of travel of an ultrasonic pulse passing through the concrete being tested. Comparatively higher velocity is obtained when concrete quality is good in terms of density, uniformity, homogeneity etc. This test is conducted by passing a pulse of ultrasonic through concrete to be tested and measuring the time taken by pulse to get through the structure. Higher velocities indicate good quality and continuity of the material, while slower velocities may indicate concrete with many cracks or voids.
Rebound Hammer Test
Rebound Hammer test is a Non-destructive testing method of concrete which provide a convenient and rapid indication of the compressive strength of the concrete. The rebound hammer is also called as Schmidt hammer that consist of a spring controlled mass that slides on a plunger within a tubular housing. When the plunger of rebound hammer is pressed against the surface of concrete, a spring controlled mass with a constant energy is made to hit concrete surface to rebound back. The extent of rebound, which is a measure of surface hardness, is measured on a graduated scale. This measured value is designated as Rebound Number (rebound index). A concrete with low strength and low stiffness will absorb more energy to yield in a lower rebound value.
Plane Table Survey
The plane table surveying is the fast method of surveying. In this type of surveying plotting of the plan and field observations can be done simultaneously. In case of plane table surveying Geometrical conditions of site are manuscript in the map sheet using plane table and alidade after that topographic details are arranged on the map. Plane table surveying is less costly than theodolite survey. •. It is advantageous in magnetic areas where compass survey is not reliable.
Bend Test of Steel Rebar
The steel bars are bent to form a specific shape such as shear stirrups, L-bars, and other shapes. therefore steel should have sufficient ductility to enable the bending of reinforcement bars without affecting the steel strength. The bending test of reinforcement steel performed to verify that steel ductility and to ensure that no fracture or cracks will occur during the bending.
Slump Cone Test
The Concrete slump test or slump cone test is to determine the workability or consistency of concrete mix prepared at the laboratory or the construction site during the progress of the work. Concrete slump test is carried out from batch to batch to check the uniform quality of concrete during construction. The slump test is the most simple workability test for concrete, involves low cost and provides immediate results.
Dynamic compaction involves the controlled impact of a crane hoisted weight, of around 10-12 tonnes, falling in a pre-determined grid pattern to improve loose, granular and mixed soils and fills Dynamic compaction is a ground improvement technique that densifies soils and fill materials by using a drop weight. The ground is subjected to repeated surface tamping using a heavy steel and concrete weight. Typically the tamper weighs between 10 and 12 tonnes, dropping in free fall from heights of up to 10 metres. The tamper is dropped a set number of times on a grid pattern over the site to form a pass. Two or three passes may be required on a site, dependent on soil type and condition. The imprints formed at each drop position are infilled with granular material after each pass.
Pile Integrity Test
Pile integrity testing is used to discover and assess flaws before further damage occurs. It is a low-strain, non-destructive method and can be used to test any form of concrete or timber pile as well as drilled shafts, as long as they are not excessively slender. It can be used either for forensic examinations on existing piles or for quality assurance for new construction. Various techniques can be used for interpreting the records of force and velocity taken under the impact of a light hammer blow. The most common technique is known as the transient dynamic response (TDR) method, which is both quick and cost-effective. Based on wave propagation theory, the top of a pile is struck with a hand-held hammer to generate a compression wave. This wave travels at a constant speed down the length of the pile and is measured with an accelerometer or geophone placed on top of the pile.
Dynamic Pile Load Test
Dynamic load testing (or dynamic loading) is a method to assess a pile‘s bearing capacity by applying a dynamic load to the pile head (a falling mass) while recording acceleration and strain on the pile head. Dynamic load testing is a high strain dynamic test which can be applied after pile installation for concrete piles. For steel or timber piles, dynamic load testing can be done during installation or after installation.
Bridge Load Test
Bridge load tests are often required to validate design calculations, extend the design service life of the structure or confirm the load capacity. Typical reasons why our clients require bridge load testing:
• To extend the design service life of the structure
• To investigate how the bridge behaves under load
• To allow an increased load on the bridge
• To determine the load capacity of the bridge
• To gather performance data on a bridge where no historical records are available
• After a structural survey identifies a potential risk
• To ascertain if a bridge is safe to use after damage caused due to impact, general deterioration or earthquake