Application prospect of drilling jumbo in tunnel construction

Combined with the main excavation methods of the current tunnel construction, the advantages and disadvantages of the rock drilling jumbo are analyzed according to the comparative analysis of the rock drilling jumbo and the traditional technology, and the feasibility and economy of the rock drilling jumbo in the tunnel excavation are comprehensively analyzed.

With the rise of labor costs and the shortage of professional and skilled personnel, the traditional pneumatic drill construction can no longer meet the national requirements for environmental protection, economy and high safety quality in tunnel construction. However, the three arm rock drilling jumbo has high construction efficiency, less environmental pollution, less energy consumption, less labor demand, low labor intensity and high safety factor, which is extremely suitable for tunnel construction at the current stage. At present, Atlas Copco of Sweden and Tamrock of Finland are the most representative manufacturers of rock drilling rigs, accounting for more than 60% of the market share. Our company has successively put into use in the construction of Xingquan Railway and Zhaolu Highway, with obvious effects, greatly improving the construction efficiency and saving production costs. This paper analyzes the advantages and disadvantages of rock drilling jumbo and comprehensively analyzes the feasibility and economy of rock drilling jumbo in tunnel excavation based on the current main excavation methods of tunnel construction.

Comparison and analysis of rock drilling jumbo and traditional pneumatic drill

① Drilling speed

The drilling speed of the drill jumbo is more than 50% faster than that of the pneumatic drill, and the overall construction progress is more than 30% faster than that of the manual excavation. It can realize simultaneous advancement of multiple holes, forming multiple holes at a time, greatly reducing the drilling time. At the same time, because the drill pipe is positioned quickly and accurately, and no auxiliary working platform is needed, it can greatly save the drilling time.

Under the construction mode of rock drilling jumbo, the equipment has no obvious advantages over the traditional process, mainly because the charging speed of the operation platform of the rock drilling jumbo is slow, and the excavation jumbo is still required to cooperate. In addition, the tunnel is located in the karst development area, and the joint fissures of the surrounding rock are developed and broken. The rock drilling jumbo is impact drilling, which causes great damage to the rock mass of the hole wall, and it is easy to collapse the hole and cannot be charged. It requires manual hole blowing to charge, so the process is increased, It counteracts the advantage of fast drilling by drilling jumbo.

② Safety performance

The density of personnel at the excavation face of the rock drilling jumbo is small, and the main operators are under the protection of the rock drilling jumbo operation room, which reduces the risk of falling rocks on the face. The drilling jumbo adopts a closed oil circuit system, which eliminates the high decibel noise emitted by the pneumatic drill when exhausting. There is no wet mist exhaust gas emitted by the pneumatic drill, and the air is relatively fresh and safer. The operator operates in the cab, which has sound insulation effect and improves the environmental conditions of the operator.

The drilling jumbo has low noise and will not discharge oil mist and harmful gas. Compared with pneumatic drilling, the drilling jumbo also has the advantages of less power consumption, high energy rate, high drilling efficiency and no exhaust noise. However, the noise sound pressure level generated by the hydraulic rock drill is still 90dB (A) high, reaching about 100dB (A), and the sound energy is mainly concentrated in the frequency range of 1kHz~5kHz, which is still within the sensitive frequency range of human ears. If no noise protection measures are taken, it will still be harmful to the health of construction personnel.

③ Construction quality

Once the drill pipe of the drill jumbo is fixed, the drill pipe can be pushed forward according to the horizontal or fixed inclination. Compared with the manually controlled drill pipe, this greatly improves the drilling quality, reduces the overbreak, and the excavation molding is better than the manual excavation.

④ Applicability

The traditional pneumatic drilling construction can deal with various levels of surrounding rock, but the drilling jumbo is only applicable to hard surrounding rock. Generally speaking, the three arm drilling jumbo is better for hard rock. However, as the surrounding rock classification of the tunnel is divided into sections, how to ensure the mechanized construction for the softer surrounding rock will be an urgent problem to be solved.

⑤ Equipment input

The drilling jumbo is expensive and the one-time cost investment is high, which requires high project cost to support. For example, the purchase cost of an Atlas three arm rock drilling jumbo is more than 7 million yuan, and the cost of accessories is also high, resulting in high maintenance costs.

⑥ Energy consumption

The drilling jumbo has obvious advantages over the traditional process. The equipment is equipped with an air compressor instead of an external air compressor, with a power of 173kW. Therefore, the equipment has obvious power saving advantages. However, the equipment has high requirements for power facilities. As the voltage will have obvious voltage drop loss with the increase of tunnel footage, the voltage will not meet the requirements of drilling jumbo when the tunnel is excavated to 700m.

Key factors for wide application of drilling jumbo

① Generally speaking, the three arm drilling jumbo is better for hard rock. However, as the surrounding rock classification of the tunnel is divided into sections, how to ensure the mechanized construction for the softer surrounding rock will be an urgent problem to be solved. According to the characteristics of "bullying the hard and fearing the soft" in equipment construction, it is better to select a tunnel with a tunnel length of more than 3km, which is dominated by Grade III surrounding rock for mechanized tunnel construction.

② Skilled technical workers are indispensable for mechanized tunnel construction. At present, China's construction enterprises use a large number of migrant workers in tunnel construction, while the technical complexity of three arm drilling jumbo is relatively high, and a large number of qualified skilled workers are required for management and maintenance. Self trained personnel, construction tasks are not full, and personnel skills are often aborted halfway. Hire operators from manufacturers, and the salary is too high. It is suggested that the group company establish a management center for professional and skilled personnel to conduct unified management and scheduling to prevent brain drain.

③ The key is to significantly reduce the cost of tunnel mechanization equipment. The country introduced tunnel mechanization construction equipment from the 1980s, and the high procurement cost and use cost of the equipment is an important reason for the failure to promote tunnel mechanization at present.

④ The state has more strict control over the safety, health and environment of tunnel construction. Mechanized tunnel construction can greatly reduce the safety risks and labor intensity of workers, and is effective in improving the construction environment such as dust.

In view of the current situation in China, due to the low salary of the pneumatic hand drill operator and the high initial investment cost of the trolley, the pneumatic hand drill still has a large cost advantage at this stage. However, with the improvement of domestic living standards and the rise of labor costs, the low-cost advantage of the pneumatic hand drill will no longer exist. In contrast to the situation abroad, the pneumatic hand drill+drilling platform method is also used for tunnel construction, However, with the rising labor costs and various environmental protection, health and safety requirements, the hand-held pneumatic drill was eventually replaced by the trolley, and disappeared in foreign tunnel construction. Of course, in the field of engineering construction, if our human resources cannot adapt to advanced equipment, advanced equipment such as full computer trolleys should be used with caution, and equipment suitable for actual construction should be selected, such as pneumatic hand drills or ordinary rock drilling trolleys.