Tips & articles

I encountered an issue with reinforcement installation on a construction site and there was a discussion regarding the following detail: In first drawing, the top reinforcement mesh is placed on top of the U bars, while in another drawing it is below the U bars, meaning the U bars hold both the top and bottom mesh. Is it critical how this detail is executed? Can the top mesh be placed on top of the U bars, or does it need to be under the U bars? Is it sufficient to ensure the proper overlap of bars only? The design standard being followed is Eurocode 2 (EC2).

Procedure Suppose A and B are two distance points whose difference of level is to be determined as in the following figure, Place the staff over point A and set up the instrument at suitable distance towards B. The suitable distance between instrument and staff can be about 25 meters. Take a sight on the staff, that reading is called Back Sight (B.S). Now, move the staff to a new position towards B and take the reading, this will be a Fore Sight (F.S). Care should be taken to make the F.S equal to preceding B.Sm, by doing this we will eliminate the effect of curvature and refraction. Now, move the instrument to a new position and take the readi…

Definition of Water Consumption (W.C) It is the amount of water consumed by a community in one day. It is usual to express water consumption in litres/capita/day. Average water consumption is usually 150 to 600 lpcd. Classification of W.C according to Use No. Purpose Use Quantity 1 Domestic Sanitary, Drinking, Washing, Bathing, Cooking, Gardening etc. ~ 50-250 lpcd 2 Commercial and Industrial Markets, Office buildings, Dental clinics, Private Schools, Garages, Workshops etc. ~ 12.2 cube m/1000 sq. m of floor are…

Object This System provides us with accurate horizontal and vertical measurements and gives us the position of observer in terms of Latitude and Longitude. Advantages This system is fast replacing with conventional methods of surveying like Triangulation, Traversing etc. It no longer requires the inter-visibility of station points. The conventional techniques are still required for detail surveying. The horizontal and vertical control can easily be established with the help of GPS. Instruments This system basically requires the receiver which is setup at the point of observation. The second part of the equipment is no of satellites which …

Sewer design requires prior knowledge of soil and site conditions to determine overburden loads that will be placed on buried pipes. Total Load = Backfill Load + Live Load Backfill Load (W): It depends upon following factors: Trench Width (B) Depth of Burial i.e, depth of fill above pipe (H) Unit Weight of Fill Material (w) Frictional Characteristics of Backfill Live Load : Live Loads on the Surface rarely influence design of sanitary sewer because of their Great Depth and Small Size. Backfill Load on Sewers Backfill load on buried pipes can be calculated using Marston's equation. W = CwB2 W = Load on t…

Chemical weathering, or chemical decomposition, involves several important reactions between the elements in the atmosphere and those in the mineral of the earth's crust. In these processes, the internal structures of the original minerals are destroyed, and new minerals are formed, with new crystal structures that are stable under conditions at the earth's surface. Water is of prime importance in chemical weathering. It takes part directly in the chemical reaction. It acts as a medium to transport elements of the atmosphere to the minerals of the rocks where reactions can occur, and it removes the products of weathering to exposed fresh rock. The chemical reactions …

All rocks, when exposed for sufficient length of time to the atmosphere, undergo decay from disintegration and decomposition, together referred to as weathering. Disintegration is the break down into small particles by the action of mechanical agents of weathering such as rain, frost etc, decomposition is the breakdown of mineral particles into new compounds by the action of chemical agents such as acid in air and in rain and river water. Denudation is the general term used for the wearing down of land areas by the processes originating and acting at the earth’s surface. It includes both weathering and erosion. In addition to the atmospheric processes, agen…

The geological work performed by rivers may be placed under three heads: Erosion, Transport and Deposition. Rivers are active agents of erosion, especially in times of floods. They carry away much material and redeposit some part of it farther downstream, the rest being transported to the sea. Some matter goes into solution in the river water. The finer particles remain in suspension and the coarse roll along the bed during floods and hence perform the work by abrading the channel of river. The work of erosion, performed by rivers, results in the widening and deepening of their valleys during their course of development. Stages of youth, maturity and old age may be d…

What is Activated Sludge? It is a FLOC (i.e body of micro-organisms gathered in a crowd) produced in a raw or settled sewage by the growth of bacteria and other organisms in the presence of dissolved oxygen and accumulated in sufficient concentrations by returning floc previously formed. Activated Sludge Process Activated Sludge Process is the biological method for treatment of wastewater. It was devised by Arden and Lockett in 1914. In this process a mixture of sewage and activated sludge is agitated and aerated in an Aeration Tank. Bacteria present in the activated sludge aerobically metabolize the organic matter present in the influent. The organic matter …

Introduction Accurate and complete subsurface information is necessary for all types of civil engineering projects, for without this information it is not possible to arrive at a rational design for structure and proper construction procedures. Structures have failed because of inadequate or misleading subsurface data, and many so called successful structures could probably have been completed at much less cost because proper consideration have been given to obtaining more complete subsurface information. Boring and Sampling Methods Auguring is a simple method of putting down holes a few inches in diameter to depths up to 20ft in soft sediments. Trial pits an…

1. Introduction Subsidence is displacement of ground surface vertically over a broad region or at localized areas. It may be either a gradual lowering or a collapse. This can have costly effect on facilities and structures over a subsiding area. Subsidence results from a number of different mechanisms. It can occur as a consequence of natural processes. The dissolving of limestone, salt, or other soluble materials creates underground openings that may collapse. Collapse may also occur in the roofs of lava tubes in areas underlain by volcanic rock. Withdrawal of fluids from subsurface reservoirs can create human-induced subsidence. This type if subsidence has resu…

1. Introduction Earthquakes are vibrations of the earth caused by the rupture and sudden movement of rocks that have been strained beyond their elastic limits. If a strained rock breaks, it then snaps into a new position and, in the process of rebounding, generates vibrations called seismic waves. Land waves produced by an earthquake have been reported with heights of more than 0.5 m and wave lengths of 8 m. The period between the passages of wave crests can be as much as 10 seconds. The vibrations can continue for as long as an hour before the wave dies out. 2. Focus and Epicenter Earthquake waves are propagated in all directions from the center of orig…

There are generally four types of earthquake induced processes: 1) Surface rupture, 2) Ground shaking, 3) Ground failure, and 4) Tsunami and Seiches occurrence. Each type has significance to a safe design of structures and is a concern for engineering geologist defining hazard levels. 1. Surface Rupture It is the actual displacement and cracking of the ground surface along a fault trace. Surface rupture is confined to a narrow zone along an active fault. Rupture may happen rapidly during an earthquake or it may not occur at all. Displacement beneath a building that exceeds 1 or 2 inches can have a catastrophic effect. Some active faults undergo imperceptibly slow…

In countries where earthquakes are of frequent occurrence, important buildings are now designed to withstand all but the most severe shocks. Structures founded on hard rocks are generally less damaged than those on soft grounds and it is found that properly designed steel-framed or ferro-concrete structures posses the highest degree of immunity from damage. Thus a rigid frame carried on a strong foundation would undergo as a whole the same movement as the ground. In soft ground a concrete raft foundation should be used. Bridges present special problems; after the Bihar earthquake of 1934, it was found that bridges with screw pile foundations had stood up the best to …

Sedimentary strata may lie horizontal as originally deposited or they may be bent into more or less regular folds, they may be displaced along fractures, or they may be traversed by planes or parting known as joints. Geologic structures influence engineering projects in many ways. Folds and faults obviously have much to do with the selection of dam sites and even such seemingly unimportant matters as the spacing of joints may have vital bearing on uplifting pressure and safety of dams. Gushed and chemically altered rocks contiguous to originating along faults may damage or destroy engineering structures. The design of deep cuts in rocks is greatly influenced of geolo…

What is an Adjustment? Adjustment of a theodolite means the operation of tightening or loosening of moveable parts to prepare the instrument for accurate measurement. It also includes other operations meant for this purpose. There are two types of adjustments for a theodolite - Temporary Adjustment & Permanent Adjustment. 1 - Temporary Adjustments These are required for each setting up of the instrument and includes following, a - Centering This is to center the instrument exactly over the ground station which is indicated by optical plummet. b - Leveling It means to make the horizontal and vertical axes in their true position. It is ind…

Normal Strain Change in the length divided by the original length is called normal strain. Shear Strain Change in angle or shape of to the original angle or shape of the body is called shear strain. Mechanical Strain gauges They can measure the surface strains in any direction. We place gauge parallel to the surface in which direction we want to measure the strains. It can measure static strains only. Optical Strain gauges: In these gauges the measurement and magnification are done optically. A system of mirrors may be used to produce large displacement on scale. It is suitable for measuring dynamics strains with a photographic recording sys…