In the construction system of rotary drilling rig, the bucket is the only core component that directly contacts the formation. Whether its selection is reasonable directly determines the drilling efficiency, construction cost, and schedule. According to the different construction strata, drilling buckets are mainly divided into two categories: soil layer drilling buckets and rock layer drilling buckets, each of which is further subdivided into various professional models.

Drill bucket for soil layers

Soil layer construction is the most common working condition of rotary drilling rigs, and the corresponding types of drill buckets are also the most diverse. Sand bucket is the most frequently used type, which adopts a single-layer bottom plate structure and is equipped with wear-resistant alloy steel shovel bucket teeth. The teeth are sharp and the cutting speed is fast. It is suitable for soft formations such as silt, fine sand, silt, clay, and fully weathered to moderately weathered mudstone. The pore diameter can reach 1.5 to 4 meters and the depth can reach 60 to 90 meters. The sand scoop bucket is equipped with two bottom plates below the cylinder, and the automatic opening and closing of the bucket bottom opening is achieved through the central axis. The lateral soil inlet makes the drilling efficiency significantly better than that of ordinary sand buckets, especially suitable for loose soil, high water content sand layers, silty loam, loose frozen soil and other structurally loose formations.

Drill bucket for rock layers

Once entering hard rock formations, ordinary bucket teeth will completely fail and must be replaced with professional rock breaking drilling buckets. The cutting tooth drill bucket is the main equipment for rock layer construction, commonly known as the "bullet head". The head is made of tungsten cobalt hard alloy, which can apply greater concentrated pressure to rocks. It is suitable for weathered bedrock, well cemented pebble and sand layers, and strongly to moderately weathered rock layers. According to the number and arrangement of spiral heads, they are further divided into various types such as single head single screw, double head single screw, double head double screw, and conical double head double screw. Among them, conical double head double screw is specialized in tackling hard bedrock, while double head single screw is more suitable for weathered rocks and frozen soils.

Core principles of selection

The iron rule for selecting drill buckets for rotary drilling rigs is "explore first, drill later, and adapt to local conditions". Before the drilling rig enters the site, the preliminary drilling tool configuration should be completed according to the geological survey report. After formal construction, several holes should be drilled to test the actual geological conditions, and then the type and layout of drilling teeth should be adjusted in a timely manner based on feedback. A graded drilling strategy must be adopted for hard rock formations. First, a small diameter cylinder drill or spiral drill is used to create a free surface, and then the hole is gradually expanded into a pile. It is important to avoid using a large diameter drill bucket to forcefully gnaw on the pile from the beginning, otherwise it will only accelerate wear and waste costs.

Esther Tian

                                                       30th,June 2026