Påldrivning: Jämförelse mellan luft- och vattendriven borrning : En utredning av jämförelser avseende slitage, logistik och driftkostnader

Sammanfattning: Skanska Grundläggning in Region Special wishes to gain an increased understanding of the extent to which it differs in the wear of percussion hammers and pilot drill crowns, depending on which driving medium is used in down-the-hole drilling, as well as logistical and economic aspects depending on the chosen method. Down-the-hole drilling means that the hammer works down in the borehole and forms one of the components at the far end of the drill string together with a drill bit. The blow of the hammer is created by air or water at high pressure. The piling method that is examined is drilled steel pipe piles, which means that a steel pipe pile is driven into the ground in step with the hammer and the drill bit's advancement. Once the desired depth has been reached, the drill string with the drill bit is pulled out of the casing and then the steel pipe pile is filled with concrete. The study aims to examine the products' lifespans and repair intervals from several different perspectives and set them against reality, as well as what the different methods have for differences regarding logistics and establishment. This is to create a basis for future decisions on the most suitable method of down-the-hole drilling. The beginning of the study consisted of qualitative preliminary interviews to identify and create a problem formulation that was dealt with via a literature study, five semi-structured interviews, eleven questionnaires, internal data from drilling protocols and purchasing. The result shows that there is some difference in wear in the hammer depending on whether it is an air or water powered system, the wear appears in different places and can have an impact on the life of the hammer. The wear that occurs most frequently on drill bit is grinding on the buttons. Geotechnical differences for various projects are a significant factor in the service life of the equipment. An air hammer requires that the air constantly being mixed with lubricating oil and that an air compressor consumes more diesel compared to a high-pressure pump for the equivalent water hammer. The handling of water that is flushed out of the borehole is considered a concern. To reduce wear on water hammers and thus fewer replacements and more repairs, a drill bit intended for water powered down-the-hole hammer should be used. DTH-drilling with an air hammer is considered an industry standard and a certain skepticism towards a water powered system may indicate inexperience.