When installing highway guardrails, the driving of piles from a design perspective mainly considers using the friction between the pile and the soil to support the upper structure. Its primary indicator is the pile's driving depth, meaning the pile tip must be driven to the design elevation. Currently, due to the widespread use of 75-type or even 85-type hammers, most piles can successfully reach the specified elevation. However, for some soil types (such as sandy soil or concrete water-stable layers), the resistance encountered when the pile penetrates can be quite significant, often resulting in the pile not reaching the desired elevation. Therefore, a minimum penetration rate for hydraulic hammers is specified in engineering projects. The so-called penetration rate refers to the average distance driven per hammer blow over 10 blows, with the unit being "mm/blow". The minimum penetration rate generally specified in projects is 2mm/blow. During the hammering process, whenever the penetration rate falls below the specified value, hammering must be stopped to investigate whether it's a case of "false limit", and then re-hammering can be conducted later.