Views: 0 Author: Site Editor Publish Time: 2026-09-08 Origin: Site
Karst caves and pebble layers are typical complex and unfavorable geological conditions, commonly characterized by loose strata, high porosity, irregular geological structures, and easy collapse and leakage of grout, which are the main difficulties in pile foundation engineering construction. The distribution of karst caves is irregular, with varying sizes and depths. The uneven hardness and poor interlocking of the gravel layer can easily lead to hole wall collapse, pile displacement, drilling jamming and other faults during the construction of rotary drilling rigs, seriously affecting the construction progress and pile foundation quality. Therefore, before formal construction, a refined pre geological survey must be carried out, combined with geological drilling reports and on-site survey data, to accurately mark the distribution location, development scale, filling medium, and core parameters such as pebble layer thickness, particle size, and compactness of the karst caves. By comprehensively identifying geological hazards and dividing dangerous construction sections, precise data support is provided for subsequent differentiated construction process adjustments and equipment parameter matching, in order to avoid construction safety hazards from the source.
In response to the geological characteristics of karst caves and pebble layers, it is necessary to abandon the standardized drilling mode of conventional homogeneous formations and adopt differentiated and dynamic rotary excavation construction technology. In the construction of gravel layers, priority should be given to using sand scoop buckets and pick tooth drill buckets to adapt to the geological conditions, reduce drilling resistance, and avoid large pebbles jamming the drilling tools. At the same time, a low-speed slow drilling and pressure stable drilling method should be adopted to prevent the disturbance and loosening of the hole wall caused by rapid drilling. In shallow karst caves and semi filled karst cave areas, slow down the drilling speed, reduce the frequency of lifting the drilling tool up and down, and prevent disturbance to the surrounding rock of the karst cave causing collapse of the hole; For large karst caves and deep karst formations, a construction method of graded drilling and segmented formation is adopted to gradually complete the drilling operation. During the construction process, the speed and pressure are adjusted in real-time based on drilling feedback and geological changes to ensure stable and controllable drilling and adapt to complex geological construction requirements.
The instability of borehole walls is a core common problem in complex geological rotary excavation construction. The loose and non cohesive gravel layer and the fractured surrounding rock of karst caves are prone to problems such as slurry leakage, hole collapse, and diameter reduction, which directly affect the quality of pile foundation formation. During construction, it is necessary to strengthen the hole wall protection system in a targeted manner, optimize the mud ratio, use high viscosity, high-density and high-quality mud, enhance the mud wall protection, slag carrying and anti-seepage capabilities, effectively seal the cracks in the pebble layer and cave fissures, and prevent mud leakage and loss. For sections with extremely poor geological conditions, pre-treatment methods such as sleeve hole protection and grouting reinforcement can be used in advance to solidify loose pebble layers and fractured karst cave surrounding rocks, thereby improving the overall stability of the formation. Maintain the stable height of the mud liquid level in the hole throughout the entire process to avoid sudden drops in liquid level that may cause collapse of the hole wall. Ensure the integrity of the borehole in all aspects and lay a solid foundation for subsequent steel cage placement and concrete pouring.
During the construction process of karst caves and pebble layers, there are many unexpected working conditions, and it is necessary to establish a sound emergency response mechanism to address various construction difficulties in a targeted manner. When encountering drilling stuck or blocked in pebble layers, it is strictly prohibited to forcefully apply pressure to lift the drilling tool. Use a small up and down shaking and low-speed rotation method to slowly get out of the trap, avoiding damage to the drilling tool and tearing of the hole wall. When encountering sudden leakage of grout or collapse of holes in karst caves, immediately stop drilling operations, quickly replenish grout and protect the holes, and simultaneously backfill with crushed stone and clay mixture to seal the cracks. Construction will resume after the formation is stable. For areas with large cave cavities and uneven filling, a pre-treatment process of advanced grouting filling and layered compaction reinforcement can be used to transform complex and unfavorable geological conditions into controllable construction strata, greatly reducing the difficulty of subsequent rotary excavation construction and improving construction fault tolerance.
The construction of complex geological rotary excavation not only requires control over the drilling process, but also requires precise management of the subsequent pile forming process to avoid quality defects in pile foundations. After the completion of drilling, timely carry out hole depth, aperture, and verticality testing, check the integrity of the hole wall, and prevent potential hazards from entering the next process. During the process of lowering the steel cage, it should be kept vertical and stable to avoid colliding with the hole wall and causing soil detachment or damage to the hole wall. The concrete pouring adopts the construction method of continuous pouring and layered vibration to ensure the compactness of the concrete, effectively fill the gaps in the karst caves and the pores of the pebble layer, and prevent quality problems such as broken piles, slag inclusion, and voids. Implementing quality control throughout the entire process, combined with complex geological construction standards and standardized operating procedures, not only effectively improves the construction efficiency of rotary drilling rigs, but also thoroughly guarantees the bearing capacity and structural stability of pile foundations, meeting the construction quality requirements of various infrastructure projects.
