When using rotary drilling rigs in hard rock formations such as granite and sandstone, the following measures should be taken to improve drilling efficiency and reduce risks:# mud drilling rig#
(1) Rotary drilling rigs with a power of 280 kN.m or higher should be selected. Drill teeth with high hardness and good abrasion resistance should be prepared in advance. Water should be added to waterless formations to reduce wear on the drill teeth.
(2) Drilling tools should be configured appropriately. When drilling large-diameter piles in such formations, a staged drilling method should be selected. For the primary stage, an extended core drill with a diameter of 600mm~800mm should be selected for direct core sampling to create a free surface; or a small-diameter auger drill can be used to create a free surface.
(3) When a sloping rock surface is encountered in hard rock formations, cleaning the hole is very difficult. Therefore, when encountering a sloping rock surface, corrections must be made before normal drilling can proceed.
Based on the practical experience of rotary drilling rigs in borehole grouting in recent years, they are applicable to most strata. However, for a specific project, the smooth and effective implementation of rotary drilling requires careful selection of the rig model and appropriate configuration of drill rods and tools, as well as the formulation and implementation of practical and reliable measures, according to the actual strata and the designed borehole diameter and depth. These measures can be summarized as follows:# mud drilling rig#
(1) Implement proper borehole wall protection measures. For boreholes requiring wall protection, mud slurry wall protection should be prioritized. For soft soil and recently backfilled soil where mud slurry wall protection is insufficient, full casing wall protection should be resolutely adopted.
(2) Select an appropriate rig model. A flexible rig with fast drilling speeds is more suitable for pile foundation construction in good strata with small depths and diameters. Larger rigs have higher power and can drill into harder strata and construct large-diameter boreholes. Using a high-power rig to drill into simple strata is inefficient; using a low-power rig makes it impossible to drill into hard rock strata. (3) Configure drilling tools appropriately and optimize the drill bit layout according to actual conditions. Before the drilling rig enters the site, the drilling tools should be configured based on geological survey data; several holes should be drilled first for trial purposes. After understanding the actual geological conditions, the drill bit layout should be optimized in a timely manner according to the actual conditions.
(4) Drill cautiously at key points. At key locations such as inclined rock faces, protruding rocks, and the top of karst caves, the drilling speed should be slowed down, and emergency measures should be prepared in advance.# mud drilling rig#
