DEVELOPMENT AND DETERMINATION OF ERGONOMICS ACCEPTABILITY OF A HAND-PUSHED VIBRATORY SOIL COMPACTING MACHINE

Abstract

Soil compacting machine found its importance in increase of soil shear strength, reduction of soil void ratio which caused soil stability and prevention of building of large water pressure in soil. These are the soil’s preliminary requirements before carrying load. The machine is very scarce due to its high purchase or rentage cost per day. Most soil compaction presently is done by ramming of the soil manually in many construction sites and in some cases compaction is left on done. Hence, the development of an indigenous soil compacting machine using locally sourced materials with very low production cost affordable by end users. The machine was designed to have a chassis mass of 32.68 kg, water reservoir of 6.57 x 10-3 m3, the discharge rate for soil wetting is 3.49 x 10-3 m3 s-1, and compacting rate of the vibrator is 5000 vpm with a power of 4.08 KW (5.5HP). The machine chassis was analyzed using solid works tools. The chassis model information are: mass 30.78 kg, volume 0.003921 m3, density of 7850 kg/m3 and weight is 301.647 N. The material properties are: Name (1023 Carbon Steel sheet), Model type (Linear Elasticity Isotropic), Default failure criterion (Max. von, mises stress), Yield strength (2.82685 x 108 N/m2), Tensile strength (4.25 x 108 N/m2), elastic modulus (2.05 x 1011 N/m2), Poisson’s ratio (0.29), Mass density (7850 kg/m3), Shear modulus (8 x 1010 N/m2) and Thermal expansion coefficient (1.2 x 10-5 Kelvin). The mesh information are: Mesh type (solid mesh), Mesher used (standard mesh), Automatic transition (off), Include mesh auto loops (off), Jacobian points (4), element size (15.3089 mm), Tolerance (0.765445 mm), Mesh quality (High), total nodes (21760), Total elements (10486), Maximum aspect ratio (9.8572), % of elements with aspect ratio < 3 (94.5), % of elements with aspect ratio >10 (0), % of distorted elements Jacobian (0), Time to complete mesh (hh: mm: ss) (00:00:03). The maximum allowable displacement of the vibrator seat is 0.00119297 mm. The significance of this is that the vibrator seat should be zero degree of movement. The maximum allowable stress that the vibrator seat should be subjected to is 958,428,688 N/m2. Stress above this will cause the failure of the seat. The maximum allowable strain that the vibrator seat could be subjected to is 2.983 x 106. Strain above this will cause the failure of the seat. The performance efficiency is 97% considering natural moisture content, bulk density and dry density of the soil. The total production cost of the machine is one hundred and sixty-seven thousand seventy-two naira (N167, 072.00) only. This brought a savings of 63% compared with the imported machine of the same capacity of: power (5.5HP) and operating weight (62 kg). The payback period for the total money invested if used for rent is less than three (3) months. The ergonomic test of the machine using GCDC-X16-4 accelerometer shows that the level of vibration transmission to the machine operator is less than 2.5 Hz which is within the construction acceptable limit and standard.