Practical Design and Construction of Machine Foundations Subjected to Impact Loads

This case study considers a construction site with weak soil (clayey and silty sands) that has a coefficient of elastic uniform compression $C_u$ less than $3\mathrm{kN}/{\mathrm{m}}^3$ ($19.27\mathrm{lb}/{\mathrm{ft}}^3$). Instead of using a deep foundation, the weak soil under the foundation was replaced with compacted limestone in order to improve the properties of the soil and increase the coefficient of uniform compression to $7\mathrm{kN}/{\mathrm{m}}^3$ ($44.96\mathrm{lb}/{\mathrm{ft}}^3$). The replacement of the soil under the machine foundation improved the elastic soil spring constants. The coefficient of elastic uniform compression of the soil $C_u$ for the vertical vibration mode was inversely proportional to the elastic settlement of the bearing plate due to external pressure, which is a function of the bearing area for the same soil. Replacing weak soils under machine foundations with strong soils, such as limestone, reduces soil settlement and the bearing area of the machine foundations while decreasing construction costs and time by up to 50% compared with constructing deep foundations.