Lecture 2 Introduction to Earthmoving Construction Methods Lecture 2 Introduction to Earthmoving Lecture 2

Introduction to Earthmoving The earthmoving process Moving soil or rocks from one location to another Processing it to meet construction requirements of location, density, moisture content, and so on. These activities include excavating, loading, hauling, placing (dumping and spreading), compacting, grading, and finishing. Efficient management of earthmoving Estimating of work quantities and job conditions Proper selection of equipment Competent job management Lecture 2

Excavating Equipment Equipment selection Major influence on the efficiency and profitability of the construction operation. The choice of equipment to be used considered for the following reasons: Increased production Reduction in overall construction costs. Carry out activities which cannot be carried out by the traditional manual methods in context of economics. Eliminate heavy manual work thus reducing fatigue and as a consequence increasing productivity. Replacing labour where there is a shortage of personnel with the necessary skills Maintain the high standards required particularly in the context of structural engineering works. Lecture 2

Equipment Costing Advantages of hiring plant: With the exception of small pieces of plant, which are usually purchased, items of equipment or plant can be bought or hired. Advantages of hiring plant: Can be hired for short periods Repairs and replacements are responsibility of the hire company. Plant is returned to the hire company after use so would be no need of finding more work for the plant to justify its purchase or retention. Can be hired with the operator, fuel and oil included in the hire rate. Advantages of buying plant Plant availability is totally within the control of the contractor. Hourly cost of plant is generally less than hired plant. Owner has choice of costing method used. Lecture 2

Excavating Equipment Production of earthmoving equipment Production = Volume per cycle G Cycles per hour Volume per cycle, represent the average volume of material moved per equipment cycle. The nominal capacity of the equipment must be modified by appropriate factor based on the type of material. The cycles per hour represents the number of cycles actually achieved or expected to be achieved per hour. Cost per unit of production = Equipment cost per hour Equipment production per hour Lecture 2

Excavating Equipment How to estimate the number of cycle per hour First method is to use the number of effective working minutes per hour to calculate the number of cycles achieved per hour. The other approach is to multiply the number of theoretical cycles per 60-min hour by a numerical efficiency factor. Management conditions include: Skill, training, and motivation of workers. Selection, operation, and maintence of equipment. Planning, job layout, supervision, and coordination of work. Job condition are the physical conditions of a job that affect the production rate Lecture 2

Bulldozers The main functions of a bulldozer are: Shallow excavations up to 300mm deep either on level ground or sidehill cutting. Clearance of shrubs and small trees Clearance of trees by using raised mould blade Acting as a towing tractor Acting as a pushing to scraper machines. Lecture 2

Scrapers Scrapers are available in three basic formate Towed scrapers Two axle Scrapers Three axle Scrapers To obtain maximum efficiency, scrapers should operate downhill if possible, have smooth haul roads, hard surfaces broken up before scraping and be assisted over the last few metres by a pushing vehicle such as a bulldozer Lecture 2

Graders A grader's main function is to finish or grade the upper surface of a large area usually as a follow up operation to scraping or bulldozing. They can produce a fine and accurate finish but do not have the power of a bulldozer therefore they are not suitable for oversite excavation work. Lecture 2

Tractor Shovels These machines are sometimes called loaders or loader shovels and primary function is to scoop up loose materials in the front mounted bucket, The tracked format being more suitable for wet and uneven ground conditions than the wheeled tractor shovel which has greater speed and manoeuvring capabilities Lecture 2

Backacters The machines are suitable for trench, foundation and basement excavations These machines will require a low loader transport vehicle for travel between sites. Backacters used in trenching operations with a bucket width equal to the trench width can be very accurate with a high output rating Lecture 2

Multi-purpose Excavators Mainly for use in conjunction with small excavation works such as those encountered by the small to medium sized building contractor. Lecture 2

Draglines The machine is primarily designed for bulk excavation in loose soils up to 30m below its own track level by swinging the bucket out to the excavation position and hauling or dragging it back towards the power unit. Dragline machines can also be fitted with a grab or clamshell bucket for excavating in very loose soils. Lecture 2

Face Shovels The primary function of this piece of plant is to excavate above its own track or wheel level. These machines can usually excavate any type of soil except rock which needs to be loosened, usually by blasting, prior to excavation. Most of these machines have a limited capacity of between 300 and 400mm for excavation below their own track or wheel level Lecture 2