Ensuring the guidance accuracy of a guided mud-water balance pipe jacking machine during construction in gravel layers is a systematic undertaking. This requires a multi-dimensional technical framework encompassing equipment adaptability, dynamic control of construction parameters, slurry system optimization, real-time monitoring and intelligent correction, personnel coordination, geological prediction, and emergency response. This ensures that the pipe jacking machine maintains millimeter-level control accuracy even under complex geological conditions.
Equipment selection and adaptation are the primary prerequisites for guiding accuracy. Gravel layers are characterized by coarse grains, high permeability, and poor soil stability, necessitating the selection of a guided mud-water balance pipe jacking machine equipped with a high-precision guidance system. For example, the combined application of a laser guidance system and a gyroscope can achieve a three-dimensional positioning error of less than 5mm. The equipment also requires a high-torque drive system to cope with the strong resistance of the gravel layer to the cutterhead. Furthermore, the cutterhead structure needs to be optimized to incorporate a combination of rollers and scrapers to enhance the crushing capability of hard particles and reduce position deviations caused by cutter sticking.
Dynamic control of construction parameters is the core means of ensuring guiding accuracy. In gravel layers, the advance speed must be strictly controlled within a range of 3-5 cm/min to avoid excessive speed leading to mud pressure imbalance or excessive slowness causing soil collapse. Mud pressure must be adjusted in real time based on the geological permeability coefficient. For example, in gravel layers with a permeability coefficient greater than 1×10⁻³cm/s, the mud density should be increased to 1.08-1.12 g/cm³ to form a stable mud film. Furthermore, the cutterhead speed must be matched to the advance speed. In hard gravel layers, the speed can be increased to 8-10 rpm, while in soft sand layers, it should be reduced to 5-7 rpm to minimize the impact of equipment vibration on the guidance system.
A refined mud system is the material foundation for guidance accuracy. For gravel layers, a 1:8 ratio of bentonite to water should be used, with 0.3%-0.5% of a polymer thickener added to create a high-viscosity, low-water-loss mud. The mud circulation system must be equipped with a four-stage treatment system. Through the tandem operation of a vibrating screen, desander, desilter, and filter press, the sand content in the mud is kept below 2%, preventing particle accumulation from clogging the guide sensors. Furthermore, slurry injection must be carried out using two simultaneous pipelines: one to balance soil pressure in front of the cutterhead, and the other to form a lubricating layer on the outer wall of the pipe segment, reducing friction that interferes with guiding accuracy.
The integration of real-time monitoring and intelligent correction technology is a technical guarantee for guiding accuracy. Modern pipe jacking machines are typically equipped with a combined monitoring system combining a total station and inertial navigation. This system collects the machine's horizontal deviation, vertical deviation, and rotation angle in real time. This data is transmitted to a central control system, where AI algorithms generate correction commands. The correction process must adhere to the principle of "small angle, high frequency." For example, each correction angle should not exceed 10° to avoid causing new deviations due to excessive single adjustments. Furthermore, the correction cylinders must be double-acting hydraulic cylinders to ensure synchronized response in both the left and right and up and down directions, minimizing posture fluctuations caused by cylinder delays.
Human resource collaboration and standardized operations underpin the management of guiding accuracy. Construction teams must establish a "five-post linkage" mechanism, ensuring real-time communication among guidance engineers, slurry engineers, equipment operators, monitoring personnel, and safety officers. For example, guidance engineers must adjust construction parameters every 30 minutes based on monitoring data, slurry engineers must test slurry performance every 15 minutes, and equipment operators must record cutterhead torque and thrust every 10 minutes. Furthermore, all operators must undergo BIM simulation training to familiarize themselves with typical deviation patterns and response strategies for gravel layer construction, thereby minimizing the impact of human error on guidance accuracy.
Improving geological prediction and emergency response systems is crucial for risk control in guidance accuracy. Before construction, drilling sampling and geophysical exploration techniques must be used to map the particle size distribution, permeability, and groundwater levels of the gravel layer to identify high-risk areas. For example, in water-rich gravel layers with a permeability greater than 1×10⁻²cm/s, triaxial mixing piles must be deployed in advance for stratum reinforcement. If a sudden sand surge occurs during construction, the emergency plan must be immediately activated. The slurry pressure must be adjusted to 1.15g/cm³, leaks must be sealed by injecting an accelerator, and the backup power supply and slurry pump must be activated to ensure the continuous operation of the guidance system.
Guided mud-water balance pipe jacking machines ensure accurate guidance during construction in gravel layers, a comprehensive reflection of equipment, processes, personnel, and management. Through the adaptation of high-precision equipment, dynamic optimization of construction parameters, refined control of the slurry system, the integration of real-time monitoring and intelligent correction technologies, standardized management for coordinated personnel, and the improvement of geological prediction and emergency response systems, these efforts effectively overcome the guidance challenges encountered during construction in gravel layers, providing reliable technical support for urban underground space development.
