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Recently studies reveal that the viscoelasticity of the asphalt layer, the transverse isotropy of each structure layer and the foundation condition of the pavement structure are important factors w...

Asphalt pavement structures in cold regions, which suffer from complicated environmental and geological conditions, such as large temperature difference and frozen soil, are prone to cracking, rutting, and moisture damage. However, most of the existing assessment methodologies focus on the vulnerability of the overall road traffic network, ignoring the impact of regional differences and pavements’ structural performance. To establish a highly targeted vulnerability analysis methodology for cold regional asphalt pavements, the concept of highway vulnerability and the assessment model composed of exposure, fragility, and resilience were proposed in this paper firstly. Meanwhile, the assessment indices and standards for exposure, fragility, and resilience were respectively discussed. Then, the calculation process for each index weight and vulnerability index was proposed based on AHP-fuzzy comprehensive assessment methodology. Consequently, the vulnerability grade of asphalt pavements in cold regions could be determined. Finally, the vulnerability assessment indices and methodology for cold regional asphalt pavements were illustrated and presented, providing a theoretical basis for asphalt pavement performance evaluation and vulnerability assessment serviced under cold regional climate.

A roadway roof has compound and cataclastic features when tunneling a roadway under a gob with top remains in downward mining. To identify the self-bearing characteristics and to develop a control strategy for a regenerated roadway roof with top remains (RRRTR), mechanical and numerical models of a RRRTR were built on the basis of a structural model of a compound and cataclastic roof. Through a theoretical analysis and numerical simulations, the formation and instability criterion of a three-hinged arch in a RRRTR were analyzed. Meanwhile, the self-bearing characteristics of a RRRTR with various crack spacing values in the top remains were studied. On this basis, a bolt-net-belt (BNB) support scenario was proposed to control the RRRTR and an on-site roof subsidence monitoring task was conducted. The theoretical and numerical analyses both indicate that a three-hinged arch exists in the roadway top remains, and it has a certain bearing capacity. The compressive failure of the hinge points is an instability trigger of a three-hinged arch that would trigger the entire failure of the RRRTR. The crack spacing values of the top remains influenced the formation and bearing capacity of the three-hinged arch. The three-hinged arch is easier to establish and has a better bearing effect when the top remains have a larger crack spacing value. The BNB support scenario could not only control the roof subsidence but also facilitate the potential self-bearing capability of the RRRTR.

The generation of nonpersistent joints in numerical specimens is not easy to achieve in some geotechnical numerical software. In this paper, the synthetic rock mass modeling method was used to construct a group of numerical specimens based on triangular grain-based model and random joint set (RJS) model in universal discrete element code. The randomly distributed nonpersistent joints have seven dominant inclination angles. Then the unconfined compressive strength (UCS) tests of the seven groups of specimens were carried out numerically to obtain some insight into the influence of dominant inclination angle on strength behaviors, failure modes and fracture development. The inclination angles of the nonpersistent RJS have fluctuant effect on the UCS of the specimens. The maximum UCS appeared when the RJS angle is 90°, and small UCS values appeared when the RJS angles are 45°, 60° and 75°. With decreasing RJS angle, the brittleness gradually changes into ductility, and strain hardening occurs. During the whole uniaxial compression process, shear fractures take the dominant role during the preliminary stage and then reduce gradually, while the tensile fractures have an inverse variation trend during the initial stage and significantly increase when the axial strain exceeds 0.6% and then keeps growing until the compression ending. The nonpersistent RJSs with small and large angles have little contribution to the shear fracture development, and only the RJSs with median inclination angles (45°, 60°) significantly promote the shear fracture propagation and development, while the RJS makes an increasing contribution to the tensile fracture propagation and development with the increase in the RJS inclination angle.

Rock mass composed of Broken Soft Rocks (BSR) under confined compression is widely distributed in geotechnical and underground engineering. To reveal the influence law of rock grain gradation and compression ratio on the shear strength properties of Regenerated Rock Mass Structure (RRMS) formed by confined compression of BSR, first, a series of compression tests of BSR with different grain gradation and compression ratios were carried out with homemade compression cylinders, through which the compression behavior of BSR was gained. In addition, the achieved Cylindrical RRMS (CRRMS) after compression was used for shear tests. Second, shear strength parameters of the CRRMS were obtained through shear tests under changing shear angle. It turns out that the CRRMS of smaller grain gradation has a better compaction degree and smoother surface. Nevertheless, the CRRMS of larger grain gradation, in contrast, has obvious gaps and a rough surface. During the compression process, the BSR of smaller grain gradation requires larger axial compression force, and the BSR of mixed grain gradations, which contain smaller grain gradation, has a better compaction effect than others. The internal friction angle of CRRMS increases with the growth in rock grain gradation, and the incremental rate of mixed grain gradations is less than those of the others. The change trend of cohesion is contrary to the internal friction angle, which decreases with the increase in grain gradation. With the homogeneous increase in the compression ratio, the internal friction angle decreases gradually, while the cohesion is contrary to the internal friction angle.

Most accessible mineral deposits are nearly exhausted. Consequently, some resources that were previously abandoned are now being considered for remining. This paper describes a case study that aims at revealing the instability mechanism and selecting the optimal control countermeasures for a cataclastic roadway regenerated roof (CRRR) during the extraction of the remaining mineral resources. Based on the structural model of a cataclastic regenerated roof (CRR) of a remaining lower slice, a modified natural arch mechanical model for a CRRR was established by considering the lateral pressure and stress concentration coefficient of the bearing arch, through which the modified bearing arch curve equation and arch rise expression were deduced. The relationship between the modified arch rise and the lateral stress was obtained through a practical case. Next, a numerical model of a CRRR, which accounted for the cataclastic features, was built in the Universal Distinct Element Code (UDEC). The development of subsidence and fractures in the roadway roof was determined through modeling under various roof support scenarios, namely no support, rock bolt (RB) support, rock bolt and cable (RBC) support and a combined support of the rock bolt, cable and steel beam (RBCS). The theoretical analysis, numerical simulation and monitoring results of the RB and RBC stress all indicated that a bearing arch existed in the CRRR and that the arch rise underwent changes during the roof hanging time and with different support scenarios. The support structure should exceed the bearing arch rise in height and should be leak proof to avoid roof leakage. After a comparative analysis of the numerical and field support effects provided by various supporting scenarios, the RBCS support scenario was shown to be the optimal roof support choice, providing a good controlling effect for a CRRR and meeting the production requirements.

The interaction between stress field and seepage field is mainly manifested in two aspects: on the one hand, the change of stress field causes the change of structural plane such as joints and fractures in rock mass, and then changes the permeability of rock mass; On the other hand, the seepage force of seepage field will change the original stress state in rock mass. The two aspects of stress field and permeation field influence and interact with each other all the time, reaching a dynamic stable state, and this dynamic relationship forms the fluid-solid coupling mathematical model. Permeability coefficient is a bridge of interaction and coupling between stress field and seepage field. Only by establishing the relationship between permeability coefficient and stress field or strain field, can the influence of stress field on seepage field be reflected and the real fluid-solid coupling analysis be realized. As a governing equation as important as the constitutive equation in the coupled numerical analysis of stress field and seepage field, permeability coefficient-volumetric strain can be used in numerical analysis to make the calculated results more consistent with engineering practice.

This study aims to analyze the dynamic response characteristics of the serviced asphalt pavement subjected to the real random vehicle loads. Fiber Bragg Grating (FBG) sensors were embedded within four types of asphalt pavements to establish pavement structural information monitoring system. Then the spatial-temporal distribution of dynamic response were obtained by data analysis. The influences of speed, axle load and temperature on the pavement response as well as the response comparison among four types of asphalt pavements were investigated. The results show that low speed, large axle load and high temperature may cause large pavement damage. The order of strain response magnitude at the bottom of asphalt layer is: Structure II > Structure III > Structure I > Structure IV. FBG measuring technology is quite reliable and beneficial for dynamic response monitoring and performance evaluation of the asphalt pavement.

Overlying key strata are regarded as plane-strained beams sandwiched by the soft rock strata in the up and down directions, and are considered elastic media. Based on the theory of the elastic foundation beam, the distribution of energy accumulation and fracture positions before and after the fracture of overlying key strata are derived, and the energy release of fractures in each stratum is calculated. To investigate the impact damage to a roadway owing to the breaking of the key stratum, panel 5312 of Jining No. 3 coal mine is taken as an example. FLAC 3D software was applied to simulate a rock burst on the roadway when the seismic source was located at the overlying key strata and different energy was released. It is shown that the side of the roadway near the working face had a high concentration of vertical stress in the coal, and the dynamic load increment generated by the source broke the static load state and triggered the rock burst. After the burst damage, the decrease in the vertical stress in the coal explained the source of the kinetic energy. With a horizontal deformation velocity of the roadway’s surrounding rocks of 1.5 m/s as the limit, the critical energy value for the burst failure caused by the fracture of each key stratum was determined.

With the dramatic increase of air traffic volume and the rapid development of civil aviation airport construction in China, asphalt layers overlaying original concrete pavement in civil aviation airports has become the primary rehabilitation scheme. However, asphalt airport pavement is prone to excessive deformation when subjected to the repeated and heavy aircraft loading, especially when coupled with high-temperature field. However, the impact of high-temperature jet wake is rarely considered in the existing structural design and analysis of airport asphalt pavement. In order to investigate the impact of high-temperature jet wake on the dynamic response of asphalt pavement, the coupling of finite element (FE) simulation of the temperature field and aircraft loading based on sequential decoupling methodology was implemented herein. Firstly, the temperature field distribution induced by the high-temperature jet wake on the asphalt pavement was simulated and analyzed by FE simulation on the ABAQUS CFD platform. Then, the temperature field distribution was integrated within the asphalt pavement structure by combining the temperature field distribution produced by jet wake and thermal conduction between ambient radiation and pavement. Secondly, the viscoelastic parameters of each asphalt layer under the obtained temperature field distribution were calculated to represent more real material properties. Finally, FE simulation of airport asphalt pavement subjected to the coupling of aircraft loading and integrated temperature field was conducted. The results show that the amplitudes of transverse strain, vertical strain, and longitudinal strain of the asphalt pavement considering jet wake together with ambient radiation are basically higher than those without consideration. Consequently, the dynamic responses of airport asphalt pavement produced by jet wake and ambient radiation should be fully considered in the design and analysis of airport asphalt pavement.

Because of the limitation of mining techniques and economic conditions, large amounts of residual coal resources have been left in underground coal mines around the world. Currently, with mining technology gradually developing, residual coal can possibly be remined. However, when residual coal is remined, caving areas might form, which can seriously affect the safety of coal mining. Hence, grouting technology is put forward as one of the most effective technologies to solve this problem. To study the grouting diffusion in fractured rock mass, this paper developed a visualization platform of grouting diffusion and a three-dimensional grouting experimental system that can monitor the grout diffusion range, diffusion time and grout pressure, then, a grouting experiment is conducted based on this system. After that, the pattern of the grouting pressure variation, grout flow and grout diffusion surface are analyzed. The relationship among some factors, such as the grouting diffusion radius, compressive strength of the grouted gravel, porosity, water-cement ratio, grouting pressure, grouting time, permeability coefficient and level of grout, is quantitatively analyzed by using MATLAB. The study results show that the flow pattern of the grout in fractured porous rock mass has a parabolic shape from the grouting hole to the bottom. The lower the level is, the larger the diffusion range of the grout is. The grouting pressure has the greatest influence on the grouting diffusion radius, followed by the grouting horizon and water-cement ratio. The grouting permeability coefficient has the least influence on the grouting diffusion radius. The grout water-cement ratio has the greatest influence on the strength of the grouted gravel, followed by the grouting permeability. The grouting pressure coefficient has the least amount of influence on the grouting diffusion radius. According to the results, the grouting parameters are designed, and a layered progressive grouting method is proposed. Finally, borehole observation and a core mechanical property test are conducted to verify the application effect. This grouting technology can contribute to the redevelopment and efficient utilization of wasted underground coal resources.

A method of slope reliability analysis was developed by imposing a state equation on the limit equilibrium theory, given the basis of a fixed safety factor technique. Among the many problems of reliability analysis, the most important problem is to find a performance function. We have created a new method of building a limit state equation for planar slip surfaces by applying the mathematical cusp catastrophe theory. This new technique overcomes the defects in the traditional rigid limit equilibrium theory and offers a new way for studying the reliability problem of planar slip surfaces. Consequently, we applied the technique to a case of an open-pit mine and compared our results with that of the traditional approach. From the results we conclude that both methods are essentially consistent, but the reliability index calculated by the traditional model is lower than that from the catastrophic model. The catastrophe model takes into consideration two possible situations of a slope being in the limit equilibrium condition, i.e., it may or may not slip. In the traditional method, however, a slope is definitely considered as slipping when it meets the condition of a limit equilibrium. We conclude that the catastrophe model has more actual and instructive importance compared to the traditional model.

Coal burst and mine earthquake frequently occur with high strength in impact roadway. Bolting system will produce a certain dynamic response under the impact load disturbance. Bolts will be damaged and rock will be instability when it serious. How to design bolting system in impact roadway is a major technical problem that has not been solved. This paper analyzes the dynamic response of bolt supporting in impact and mechanized caving roadway by FLAC3D.Then it gets the bolt axial force, shear stress of anchor agent and deformation of roadway variation with time and space. This study provides the design basis for the optimizing impact roadway bolting and improves control effect of bolting system. The results show that under the impact load the degree of dynamic response of anchor and roadway has great relationship with the distance between the measuring point and the power source. It reflects sensitively. Tilt bolts affect greatly. Threads and components of bolt tail are easily damaged, while anchoring agent prone to shear failure. Therefore, the bolt of rock burst roadway should have high prestress and high strength. While the choice of bolt end member, anchoring agent, the let press member and bolt elongation with high energy absorption properties are also very important.