FAN Jun ,ZHANG Jialin ,QIN Yuan ,WANG Hao ,GAO Yanan ,PEI Yongzhi

(1. The Administrative Centre for China’s Agenda 21,Beijing 100038, China;2.School of Mechanics and Civil Engineering, China University of Mining and &Technology, Xuzhou 221116, China)

Abstract:The Deep Resources Exploration and Mining(DREAM) grant program,within the framework of The National Key Research and Development Program grants,is a pillar to implement China’s science and technology strategy in the area of deep resources exploitation.To tackle the insufficient of theories and technologies for the 1000-meter-deep mining,a section of mining,covering the research of basic theories,general technologies and application demonstration,was arranged in the layout of DREAM under the principle of“whole chain design,integrated implementation”.In the aspect of basic research,DREAM mainly focused on the deep rock mechanics and mining theory,such as the in-situ mechanical behavior of deep rock,deep high stress induction and energy regulation theory.For the general and key technologies,DREAM supported the research on the mine construction and hoisting,excavation,rock breaking,mining methods and mining safety according to the characteristics of coal and metal mines.For the demonstration application,taking green,safe and efficient as the starting point,DREAM aimed at the green,safe and high efficiency mining,and the demonstration and leading role projects such as the low-waste and high-efficiency back fill mining.Since 2016,10 R&D projects have been funded,and 122 institutional participants with a total budget of RMB 235 million from the central government and RMB 480 million from enterprises as well as local governments have been involved.It is expected that the mining section of DREAM would contribute to establishing the theory and technology system in the area of deep mining and promoting the ability of deep resource exploitation in China.

Keywords:resource of deep earth;mining;theory;general technology;application demonstration

The National Key Research and Development Program is a great accomplishment of deepening the management reform of central government science and technology financing plans.It currently serves as one of the principal channels for the Chinese government to fund major research on social welfare,scientific problems,and R&D of general technologies and products,as well as major international scientific and technological cooperation[1].The program consists of several purposeful and well-defined grant programs[2].Since 2016,some 70 grant programs have been launched[3],with a total budget of RMB 102.4 billion from the central government.

The Deep Resources Exploration and Mining(DREAM) grant program,initiated in 2016,aimed to break the key scientific bottlenecks of deep resources mineralization,accumulation,prediction and evaluation in China,construct the theory and technology system for deep resources mining,develop the technology system of three-dimensional air-ground-underground exploration and key technologies for deep mining,and build practice platforms for deep resources exploration,contributing to China in improving the innovation ability of the resources exploration and mining industry,enhancing its core competences,and ensuring the security of national energy resources[4].Upon layout,the demand-driven and goal-oriented DREAM was guided by major national development strategies and planning tasks from top to bottom,with consideration to the needs of R&D tasks from departments,local governments,and industries from the bottom up.In line with the principle of“full chain design,integrated implementation”,it painted the whole picture on the research of basic theories and application fundamentals,general technologies and equipment,and application demonstration,centering on the theoretical,technical and application problems that urgently need to be tackled in the deep resources exploration and mining sector in China.

Enhancing the capabilities in deep resources exploration is a vital component of China’s deep earth strategy,and represents a key“weapon”to help“move towards the Earth’s deeper interior.”DREAM specially developed a section of mining[5],therefore,to energetically explore new principles,new processes,new technologies,and new equipment related to deep resources(mainly coal and metal mines),based on the characteristics of deep resources and the actual needs of deep mining in China.This would provide scientific and technological support and reserves for the development of deep mining practice in China.

1 Research background and purposes

With the gradual depletion of shallow resources,the development of deep resources has become the focus of the major mining powers worldwide.While Australia,Canada,South Africa and other countries have advanced the mining of mineral resources at depths ranging from 2 000 to 4 000 m,China is well on track to normalize mining at depths between 1 000 and 2 000 m.Tapping into the Earth’s deep interior,deep resources exploitation will have to face major challenges such as high and low stress,high water pressure,high ground temperature,great well depth,and strong disturbance[6].On a global scale,deep mining practice falls short on systematic theoretical guidance,with the process technology still in the exploratory stage,and insufficient mining equipment R&D suitable for deep resources.Its scientific development needs to focus on the following issues:the establishment and improvement of deep rock mechanics and mining theories;the process,technology and equipment that fit into the deep environment and satisfy the needs of projects;and high-tech solutions for systematic deep mining that are safe and green and enable cost reduction and efficiency gain[7-11].

DREAM had the research purposes targeted at the development of deep rock mechanics and deep mining theories,the building of a basic theoretical system for deep resources mining,and the support for mining at greater depths at scale;and at making breakthroughs in deep shaft construction,upgrading key technologies and equipment,studying deep rock control technologies,carrying out the R&D of the technologies for safe and efficient mining at scale,developing unmanned deep mining technologies,and providing theoretical and technical support for 1,500-meter deep mining.When deploying the tasks of the research,overall consideration was given to the connection of the research on basic theories,general technologies,and application demonstration,in a bid to achieve rapid transmission and mutual promotion between upstream and downstream R&D activities.

2 Project establishment status

2.1 Characteristics of the research

Based on the type of major research,the projects focusing on the research of basic theories and application fundamentals accounted for about one fourth of the total,the projects centering on the research of general and key technologies and equipment were responsible for about two thirds,and those highlighting the research of application demonstration were the least.From the perspective of funding distribution,the research of basic theories and application fundamentals represented around 29% of the total funding,the research of general and key technologies and equipment about 68% at RMB 150 million,and that of application demonstration only 3%.On the whole,DREAM provided more support,on average,for the projects focusing on the research of basic theories and application fundamentals,with each at RMB 4.58 million on average,while providing the least support for those highlighting the research of application demonstration,with each at some RMB 2.76 million,for which the funding was mainly from the organization’s own funds or other supporting funds.

2.2 Distribution characteristics of the undertaking units

Seen from the distribution of projects leading units,projects undertaking units,and funding,universities and enterprises are the main players of research tasks(as shown in Table 1).

Among the projects undertaken by universities,about 36% were based on theoretical and methodological research,and 61% were focused on the R&D of general technologies.Among the projects undertaken by enterprises,around 13% mainly carried out theoretical and mechanism research,72% principally focused on breakthroughs in key technologies,and 15% implemented application demonstration.The main tasks undertaken by research institutes were to make breakthroughs in key technologies.

3 Research contents and key technologies

3.1 Research on basic theories

As mineral resources mining continues to expand to depths below 1 000 m,the serviceability oftraditional mining theories based on the development of shallow and medium depth resources in the past will face major challenges.As a matter of fact,the practical activities of deep mining projects are ahead of the systematic exploration of related basic theories,and there is blindness,inefficiency and uncertainty in project practice to some extent[6-7].Aiming at the deep environment of 1 000-2 000 m,DREAM took a systematic approach to study the mechanical behavior of rock under the action of mining-induced stress,so as to enable the matching of the deep in-situ stress environment with the in-situ mechanical behavior of rock.Building research platforms for the deep rock mechanics and mining theories and creating new theoretical system of deep rock mechanics underlie the scientific development of deep mining and the comprehensive improvement on the ability of deep resource exploitation in China.The basic scientific problems DREAM focused on include:the in-situ mechanical behavior of deep rock,visualization of stress field and energy field of rock under mining-induced stress conditions,long-term stability behavior of surrounding rock in deep underground spaces,theory of multiphase and multi-field rock mechanics under the conditions of strong disturbance and strong aging,and deep high stress induction and energy regulation theory,among others(Fig.1).The relevant research contents and purposes are shown in Table 2.

Fig.1 The organization and main tasks of the mining section of DREAM

Table 1 The distribution of projects undertaking units and funding

3.2 Research on key technologies

Complicated geological conditions such as deep high stress,high water pressure,and variable stratum not only lead to“abnormal”mechanical behaviors of rock,but also bring engineering problems that traditional mining technologies cannot be fully applied or even fail.Deep mining places higher requirements on engineering technologies such as mine construction and hoisting,underground excavation and rock breaking,mining methods and techniques,mining safety and protection,and engineering technologies compatible with the deep environment are in urgent need of breakthroughs and development.In response to the needs of technologies for coal and metal mining,DREAM conducted targeted task deployment(as shown in Table 3).

Table 2 The research contents and purposes of scientific problems of deep resources mining

Table 3 The contents and targets of research on engineering technical problems on deep resources mining

Continuation Table

As far as coal resources mining is concerned,in view of the technical difficulties of deep mine construction,DREAM focused on achieving breakthroughs in the control of large deformation of surrounding rock in the process of deep mine construction,the collaborative control of roadway bolting-modification-distressing under the disturbance of enhanced mining in 1 000-meter deep shaft,and other aspects.In response to the technical requirements for safe and efficient mining of deep coal resources,it laid emphasis on the research and development of stability control and intelligent coal caving technologies for overlying strata in large-space stopes with ultra-thick coal seams.Aiming at the technical requirements for green mining and environmental protection in mines,it stayed focused on supporting the research and development of integrated mining technology for deep coal mining,selection,and filling.In terms of the mining of metal mineral resources,in response to the technical requirements for the mining of deep metal mines at scale,DREAM mainly aimed to tackle such key technologies as in-situ efficient rock breaking of deep metal mines with high stress and strong compression in hard rock,advance fracturing and precise blasting of combined holes in deep rock with high energy storage,and non-explosive and intensive continuous mining of deep hard rock.In view of the high recovery rate of deep metal mineral resources and environmental coordination and protection,the focus was on the research on the technical system for the stability control of the back fill and rock system used in deep metal mines.

3.3 Research on application demonstration

In recent years,China has been actively exploring deep mining technologies for mineral resources,and the technology for deep shaft has been partially applied in mine design across the country.However,the combination of innovation in basic theories and R&D of engineering technologies and equipment with engineering practice is still not close enough,and leading demonstration projects that can provide verification of individual technologies and system solutions for 1 000-meter deep mining still go short.Therefore,when deploying research,DREAM placed special emphasis on the combination of industry,university,research and application,and the actual needs of engineering construction as the traction to improve the pertinence of theoretical research and the practicability of equipment manufacturing achievements.In response to the urgent need for industrial upgrading and technical directions with implementation conditions,DREAM clearly put forward the requirements for technology demonstration and application.By driving the construction of industry-leading demonstration projects,it promoted the improvement of China’s deep resources mining level and the realization of science-based production capacity.Taking green,safe,and efficient as the starting point,the demonstration projects DREAM focused on supporting include:high-efficiency well completion and hoisting in deep mines,deep low-waste and high-efficiency mechanized back fill mining,multi-equipment multi-system cluster control in deep metal mines,mining of 1 000-meter deep shafts in coal mines with a 350-meter ultra-long working face,and green mining and ecological protection in large-scale coal bases.

4 Conclusion

In response to the major demand for science and technology in the transformation and upgrading of China’s resources mining industry,DREAM has deployed a number of research tasks about innovation in basic theories,R&D of key technical equipment,and application demonstration in a systematic way.By continuously tackling key technologies,it will strive to build the theory and technology system for deep resources mining that adapts to the characteristics of resources in China,put forth effort to develop deep rock mechanics as well as new principles and theories of mining,and focus on making breakthroughs in a number of cutting-edge core key technologies and deep shaft construction techniques.Through the systematic integration application of theories and equipment manufacturing achievements,it will look to deliver individual technologies or technology solutions to overcome high stress,high water pressure,high ground temperature,great well depth,strong disturbance,and other problems facing the deep mining of coal and metal mines,so as to contribute to promoting the ability of deep resource exploitation in China.