The principles of fracture development during underwater blasting are examined based on explosion and impact dynamics, fluid dynamics, fracture dynamics, and field testing. The research reveals that the fracturing of the surrounding rock during underwater blasting is due to the combined action of shock and stress waves for the initial rock breakage and subsequent water expansion. The fracture development model for the surrounding rock of a drilling hole during underwater blasting is established. The rock fracturing range under the combined action of shock and stress waves is developed, as well as the fracture propagation rules after the wedging of the water medium into the fractures. Finally, the results of deep-hole underwater blasting tests on large rocks confirm the efficient utilization of explosive in the hole to improve the safety conditions. Accordingly, safe and static rock breaking under the detonation of high-effect explosive can be achieved. In addition, super-dynamic loading from the explosions and static loading from the water medium in the hole can be adequately combined for rock breaking.

In order to strengthen students' practical ability and cultivate their innovation consciousness, subject competition system is established using subject competition as carrier. The paper analyzes and explores the operation mechanism of subject competition system on cultivating college students' innovative and practical ability, and proposes strategies and approaches to promote the cultivation of college students' innovative and practical ability through subject competition, which is of great significance to the improvement of college students' practical teaching quality.

In terms of surrounding rock control in large section open-off cut, open-off cut No. 5206 in a mine is selected as study case. The principal stress difference, deformation and fracture field are studied in the process of width from 6 m to 10 m with UDEC. Research results show that: the principal stress differences increase gradually in shallow part and decrease in depth. With the width increasing, the maximal principal stress difference maintains a constant level at first, then decreases gradually in the roof, and decreases at first, then remains constant in the floor, and increases gradually in the rib. The moving range of peak: rib>roof>floor. The curve of displacement in roof decrease exponentially, but has obvious inflection point, which decrease terracedly in the floor. The maximal surface displacement: roof>side walls>floor. The fracture field is divided into three areas: fracture transfixion area, fracture area and microfracture area, which are all distributed as semi-ellipse, the extent of cut through: middle part>two sides and shallow part>deep part. It is believed that high-performance bolt hold the slippage of fracture effectively. The double truss cable can be anchored in the shoulder angle area, which has no fracture, and pre-tension overlays the area. Also, the double truss cable can close the shallow part of roof and reduce principal stress difference. Based on above, a high strength and high pre-tension bolting support scheme of band net and double truss anchor are proposed. The open-off cut achieves self-stabilization after 10 days when it is dug out, the total roof separation is 3 mm, and the roof-to-floor relative convergence is 125 mm, both sides relative convergence is 94 mm.

Compared with I-shaped and U-shaped supports in soft rock roadway, concrete-filled steel tubular (CFST) support, as a new supporting form, has stronger bearing capacity with reasonable price. So it is becoming more and more popular in roadway supporting of coal mine in China. In this article, the surrounding rock in soft rock roadway was classified into three different types: hard rock in deep coal mine, soft surrounding rock, extremely soft surrounding rock. And, according to the characteristics of deformation failure of the CFST support and the surrounding rock in the industrial tests, three different strength assessments, including assessment of axial compressive strength, assessment of lateral flexural performance, assessment of hardening rate of core concrete, were proposed through mechanical analysis and laboratory tests for the three different types of the surrounding rock, respectively. Moreover, aimed to insufficient flexural strength of the support or low hardening rate of the core concrete in some of the roadway supporting, strengthening lateral flexural performance or making early strength concrete was necessary for the above unfavorable situations. The laboratory test results showed that the ultimate bearing capacity for the CFST support with φ194*8mm of steel tube reinforced by φ38mm round steel was 31% greater than that of the unreinforced one, 177% greater than that of the U-shaped one with equivalent weight per unit length.

The soft rock roadway is classified by uniaxial compressive strength of rock and water-physical properties, which includes hard surrounding rock in deep mine, soft surrounding rock, and extremely soft surrounding rock. Aimed to the situation of being hard to support the extremely soft rock roadway, with combination of the specific project of return airway crossheading roadway of sea area NO.2 mining district in Beizao coal mine, a compound roadway supporting technology based on the concrete-filled steel tube support, reinforced concrete lining, with combination of yield supporting technology was used for this specific project, for which the mechanical model of the pressure-bearing ring structure was analyzed and calculated by using fixed-end arch theory in structural mechanics and Lame formula in Elastic theory. The field test results showed that this new compound roadway supporting technology was an ideal method to support the extremely soft rock roadway, which could control the deformation of roadway and realize the stability of roadway, effectively.

Inner Mongolia's xilingol league area of chagannaoers main inclined shaft is extremely soft rock roadway with the properties of 0.12 ~ 5.12MPa in uniaxial compressive strength of rock, 60.6% in clay mineral content and 82% of clay mineral composition is montmorillonite, and with the feature of argillation and expansion by absorbing water in surrounding rock. The two previous supporting schemes for this roadway were double16a I-beam and 650mm concrete layer as the first scheme, and close U36 steel stents as the repairing scheme, respectively. Both of them were failed to control deformation failure of surrounding rock. In this paper, a new supporting scheme was proposed by testing mechanics parameters and mineral composition of surrounding rock, analyzing hydraulic properties of surrounding rock and deformation failure, and evaluating surrounding rock load. This new scheme consists of high strength pressure-bearing ring supporting technology based on concrete filled steel tubular support and surrounding rock partial pressure-releasing technology. Aiming at deformation of side walls of the main inclined shaft roadway, a test was carried out to study the bending resistance of the support and improve the support. The industrial test showed that the new supporting scheme can effectively control the deformation of the main inclined shaft surrounding rock and realize long-term stability of roadway.

Part of the east wing belt roadway in -450 level east, NO.1 mining area, Dashu village coal mine, Jizhong Energy Fengfeng Group was under the 172102 working face’s stop mining coal pillar. The phenomenon of the stress concentration was obvious, the pressure of the roadway was large and the surrounding rock damaged severely. Concrete filled steel tube supports were used in stress concentration region. The supports type was φ194×8mm, and distance between supports was 800mm. They were of rapid construction speed, better supporting effect. The numerical simulation results also showed that the concrete filled steel tube supports can reduce deformation of the roadway surrounding rock in stress concentration region effectively.

The coal roadways with water spraying usually have large surrounding rock deformation or roof abscission layer, especially to the roadways with compound rock strata roof, which could lead to sudden roof caving accidents, so it is imperative to research the roof characters and the corresponding controlling methods. In this paper, we firstly analyze the main reasons and characters of the roof deformation or its stability failure with bolt and cable supporting, and then the mechanical properties of the roof are tested in the lab, which could afford detailed datum to the further analysis. Based on the comprehensive researching results of this complex roof, a set of measuring device for the value of water spraying in single roof hole is developed and then applied to a typical coal roadway. Finally, some effective controlling methods are put forward to prevent from the large deformation of the roadways.

In this paper we describe the necessity and significance of coal preparation plant inspection robot, propose the robot design requirements and design the system framework of hardware and software. Then we use RecurDyn software to simulate and analysis the stability and fitness of the inspection robot in coal preparation plant complex environment based on virtual prototype technique.

This paper proposed the methods for distribution and safety check of bearing force of multi-layer reinforced concrete structure in construction and construction load in related floors.It solved the problems of no evidence and experience dependence construction in installation and backout of formwork-supporting system for multilayer concrete structures.

According to the failure phenomenon and test data in the orthogonal quasi-static test,the characteristics of deformation and flexural strength of circular reinforced concrete bridge columns are studied.And the displacement ductility,effective stiffness,stiffness degradation and capacity of accumulative energy dissipation to ultimate displacement state of bridge columns subjected to low-cyclic loading have been evaluated,so as to investigate the influence of factors such as shear-span ratio,axial-load ratio,and longitudinal reinforcement ratio and spiral reinforcement ratio on ductility performance of bridge columns.Finally,some useful conclusions are found out for the ductile anti-seismic design of highway bridges.

Two new concepts, limit neighbor of rock strength and perturbation effect of rock rheology were explained. Besides, the rock rheology perturbation effect mechanism was analyzed. And the constitutive equation of accumulated deformation disturbed by the rock was founded. According to the equation, integrated with the rock rheology and disturbed effects test results, the equation of the third lateral perturbation deformation and perturbation times was established. In addition, combining with the geological data of Longkou sea area tunnel which is a typical soft rock project, the peak shifting identification standard was proposed in surrounding stress field. Moreover, the surrounding rock stress field evolution law was concluded when the blasting construction was operated in the next runnel.

Traditional supports are difficult to maintain the route work of roadway in deep well due to dynamic pressure propagation within soft rock. To tackle this problem, concrete-filled steel tube support is developed; and further the mechanical properties of the support are tested in laboratory. The experimental supports are composed by four sections of φ140 mm × 4.5 mm steel tube, with concrete C40, and joints with casing linkage. Under the conditions of lateral constraint and vertical point load pressure, the ultimate bearing capacity of experimental support is about 1504.1 kN; and the vertical ultimate compressive deformation reaches 82.65 mm, resulting in failure mode of steel tube. Compared with the U-shaped steel support, concrete-filled steel tube support holds not only high supporting capacity, but also with a competitive price. So concrete-filled steel tube structure may have an extensive application to coal mine roadway.

Gushan iron mine of Ma-an-shan steel group has a typically complex geological condition of igneous rock. The tunnel workable stability can't be obtained by traditional support. In order to make reasonable support design, it is specially studied for the tunnel junction near the south working face at the shaft bottom of - 300 m in Hou He-mu-shan mine area. According to the practical geology characteristic and the support mechanism of bolting-shotcreting, bolting-grouting and pre-stressed anchor cable, the dynamic superposition of "tri-anchor" support method, bolting-shotcreting for the first flexible support and bolting-grouting and prestressed anchor cable for the secondary fortified support, are designed for the support in this project. The good technical and economical effects are obtained. The results of this research show that the fragmented and dilatable surrounding rock should be rapidly closed over, and the first flexible stress-release support should be quickly exerted for the construction at tunnel junction disturbed by heavy excavation, besides, the combined fortified support by bolting-grouting and pre-stressed anchor cable is advised for the support of large section tunnel or the surrounding rock with large broken zone.

In East China, circular vertical shafts are usually adopted for mining coal because the surface soil strata are very thick and rich of ground water, whose thickness is generally 200-400 m. Especially, the thickness of surface soil strata in Juye coal field under construction is about 800 m. The shaft lining is made of two-double reinpressured concrete. But in recent 3 0 years, about 100 vertical shafts in these mine areas have experienced serious deformations and ruptures. The reasons to cause failure in shaft lining are summarized as follows: The strata settlement resulting from water drainage of the aquifer makes the shaft lining subject to downward vertical additional pressure (namely, tangential load) which induces the ruptures. In the past, the designing and computing in shaft lining were unreasonable because of the adopted plane model was based on the maximal radial load in the section in shaft lining in which the additional vertical pressure and the change of radial load distributed along the shaft were not considered. In this paper, based on spatially axisymmetric model, the computing of the load caused by strata settlement due to water drainage and computing of stress in finite or infinite long composite shaft lining and the thickness in shaft lining are given by the expansion method of Fourier series and Fourier-Bessel series. It provides a basis for design of the spatial model in shaft lining in thick overlay soil strata.