The Scope Of Application Of Rotary Excavators And The Drawbacks in Construction

Rotary Drilling Rigs, also known as Rotary Drilling Rigs, are a type of construction machinery that has only been developed in recent years and is suitable for drilling operations in building foundation engineering; Green construction technology;. Widely used in pile foundation construction of railways, highways, bridges, municipal construction, urban civil buildings, etc., with different drilling tools, suitable for dry (short spiral), wet (rotary bucket) and rock (core drilling) drilling operations. Rotary excavators have excellent construction quality, outstanding environmental protection characteristics, less dust and mud pollution, flexible maneuverability, high construction efficiency, fast drilling speed and multifunctional features. Rotary excavators are basically suitable for the soil and geological conditions in most regions of China, with a wide range of applications, and can meet the needs of high-rise building foundations, bridge construction, and other engineering projects. At present, rotary excavators have been widely promoted in various drilling and grouting pile projects.

Scope of application of rotary excavator:

From the perspective of suitability for geological strata, it is suitable for both cohesive soil, sandy soil, and silty soil, as well as artificial backfill soil, strata containing some pebbles and gravel, and weathered rocks with low strength.

From the perspective of drilling methods, both wet drilling and dry drilling can be used.

3. In terms of the types of drilled piles, they can be drilled with straight or inclined holes, with a maximum pile diameter of up to 2.5m and a maximum pile length of up to 100m.

4. In terms of construction space, it is not necessary to provide a large working surface for operation, which is incomparable to other bored piles.

From an environmental perspective, construction noise is low, does not pollute the environment, and is suitable for construction areas with high environmental protection requirements.

The disadvantages are as follows:

1. Due to its large size, it has strict requirements for the venue. The self weight of a rotary excavator during operation is generally around 70 tons, but its track has a contact area with the ground of about 7.0 square meters. Therefore, the required foundation bearing capacity is around 100 kPa, especially in fill areas. If the surface has not been hardened or replaced, and there is abundant surface water or rainy season construction, careful consideration should be given. Otherwise, it is very difficult to use a rotary excavator for construction by simply moving the machine, which seriously wastes the advantages of machinery.

2. Poor hole wall protection. Due to the fast drilling speed of the rotary excavator, it mainly relies on cutting soil for drilling, and the hole wall protection is inferior to that of drilling and punching piles. Especially in backfill and soft soil layers, collapse of holes, drilling and jamming are prone to occur and should be taken seriously. During construction in backfill and soft soil, the drilling speed should be controlled, and more and less drilling should be carried out as much as possible to meet the requirements of wall protection. At the same time, during construction in soft soil, attention should be paid to the drilling depth, and the depth of one drilling should not be too large.

3. Negative pressure is easily generated in the pores of soft soil. The contact surface between the rotary excavator drill barrel and the soil is relatively large. If the drilling depth is large in soft soil, negative pressure is easily generated during the lifting process of the drill bucket, which increases the pulling load on the rotary excavation pile body and has adverse effects on the stability of the hole wall, easily leading to hole wall shrinkage.

4. For viscous soil and loose sandy soil in flow plastic state, the mud problem must be solved and carefully selected.