查看更多>>摘要：3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechan-ical properties of 3D-printed specimens to make them proportionally similar to natural rocks.This study investigates mechanical properties of 3D-printed rock analogues prepared by furan resin-bonded silica sand particles.The mechanical property regulation of 3D-printed specimens is realized through quanti-fying its similarity to sandstone,so that analogous deformation characteristics and failure mode are acquired.Considering similarity conversion,uniaxial compressive strength,cohesion and stress-strain relationship curve of 3D-printed specimen are similar to those of sandstone.In the study ranges,the strength of 3D-printed specimen is positively correlated with the additive content,negatively correlated with the sand particle size,and first increases then decreases with the increase of curing temperature.The regulation scheme with optimal similarity quantification index,that is the sand type of 70/140,additive content of 2.5‰ and curing temperature of 81.6 ℃,is determined for preparing 3D-printed sandstone analogues and models.The effectiveness of mechanical property regulation is proved through uniaxial compression contrast tests.This study provides a reference for preparing rock-like specimens and engineering models using 3D printing technology.
查看更多>>摘要：2D profile lines play a critical role in cost-effectively evaluating rock joint properties and shear strength.However,the interval(ΔIL)between these lines significantly impacts roughness and shear strength assessments.A detailed study of 45 joint samples using four statistical measures across 500 differentΔIL values identified a clear line interval effect with two stages:stable and fluctuation-discrete.Further statistical analysis showed a linear relationship between the error bounds of four parameters,shear strength evaluation,and their corresponding maximum ΔIL values,where the gradient k of this lin-ear relationship was influenced by the basic friction angle and normal stress.Accounting for these factors,lower-limit linear models were employed to determine the optimal ΔIL values that met error tolerances(1％-10％)for all metrics and shear strength.The study also explored the consistent size effect on joints regardless of ΔIL changes,revealing three types of size effects based on morphological heterogeneity.Notably,larger joints required generally higher ΔIL to maintain the predefined error limits,suggesting an increased interval for large joint analyses.Consequently,this research provides a basis for determining the optimal ΔIL,improving accuracy in 2D profile line assessments of joint characteristics.
查看更多>>摘要：Underground constructions often encounter water environments,where water-rock interaction can increase porosity,thereby weakening engineering rocks.Correspondingly,the failure criterion for chem-ically corroded rocks becomes essential in the stability analysis and design of such structures.This study enhances the applicability of the Hoek-Brown(H-B)criterion for engineering structures operating in chemically corrosive conditions by introducing a kinetic porosity-dependent instantaneous mi(KPIM).A multiscale experimental investigation,including nuclear magnetic resonance(NMR),X-ray diffraction(XRD),scanning electron microscopy(SEM),pH and ion chromatography analysis,and triaxial compres-sion tests,is employed to quantify pore structural changes and their linkage with the strength responses of limestone under coupled chemical-mechanical(C-M)conditions.By employing ion chromatography and NMR analysis,along with incorporating the principles of free-face dissolution theory accounting for both congruent and incongruent dissolution,a kinetic chemical corrosion model is developed.This model aims to calculate the kinetic porosity alterations within rocks exposed to varying H+concentra-tions and durations.Subsequently,utilizing the generalized mixture rule(GMR),the kinetic porosity-dependent mi is formulated.Evaluation of the KPIM-enhanced H-B criterion using compression test data from 5 types of rocks demonstrated a high level of consistency between the criterion and the experimen-tal results,with a coefficient of determination greater than 0.96,a mean absolute percentage error less than 4.84％,and a root-mean-square deviation less than 5.95 MPa.Finally,the physical significance of the porosity-dependent instantaneous mi is clarified:it serves as an indicator of a rock's capacity to lever-age the confining pressure effect.
查看更多>>摘要：Blasting operations,which are crucial to open-pit mine production due to their simplicity and efficiency,require precise control through accurate vibration velocity calculations.The conventional Sadowski for-mula mainly focuses on blast center distance but neglects the amplification effect of blasting vibration waves by terraced terrain,from which the calculated blasting vibration velocities are smaller than the actual values,affecting the safety of the project.To address this issue,our model introduces the influ-ences of slope and time into Sadowski formula to measure safety through blast vibration displacement.In the northern section of the open-pit quartz mine in Jinchang City,Gansu Province,China,the data of a continuous blasting slope project are referred to.Our findings reveal a noticeable vibration amplification effect during blasting when a multi-stage slope platform undergoes a sudden cross-sectional change near the upper overhanging surface.The amplification vibration coefficient increases with height,while vibra-tion waves within rocks decrease from bottom to top.Conversely,platforms without distinct cross-sectional changes exhibit no pronounced amplification during blasting.In addition,the vibration inten-sity decreases with distance as the rock height difference change propagates.The results obtained by the proposed blast vibration displacement equation incorporating slope shape influence closely agree with real-world scenarios.According to Pearson correlation coefficient(PPMCC)analysis,the average accuracy rate of our model is 88.84％,which exceeds the conventional Sadowski formula(46.92％).
Ahmad F.ZueterMohammad ZolfagharroshanNavid BahraniAgus P.Sasmito...
643-654页
查看更多>>摘要：Current practice of underground artificial ground freezing(AGF)typically involves huge refrigeration sys-tems of large economic and environmental costs.In this study,a novel AGF technique is proposed deploy-ing available cold wind in cold regions.This is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer.A refrigeration unit can be optionally integrated to meet additional cooling requirements.The introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration load.This design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the thermosyphon.Two Canadian mines are considered:the Cigar Lake Mine and the Giant Mine.The results show that our pro-posed design can speed the freezing time by 30％at the Giant Mine and by two months at the Cigar Lake Mine.Further,a cooling load of 2.4 GWh can be saved at the Cigar Lake Mine.Overall,this study provides mining practitioners with sustainable solutions of underground AGF.
查看更多>>摘要：Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of aban-doned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(M1P),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40％,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deteri-oration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.
查看更多>>摘要：Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detection(DPD)system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod,geophones at the tunnel face,a laser rangefinder,and an onsite computer.A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling.A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method.Time-frequency anal-ysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seis-mic exploration wavelet.A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained.Both the borehole core and optical image validate the inverted P-wave velocity field.A numerical simulation of a checkerboard benchmark model is used to test the tomography method.The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.
查看更多>>摘要：Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective control.Physical experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving(LTCC).A numerical model is established using the material point method(MPM)and the strain-softening damage constitutive model according to the structure of the physical model.Numerical simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic fracturing.The results show that ground hydraulic fracturing releases the energy and stress of the target stratum,resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing stratum.Ground hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures,dissipates the energy consumed by the fracture of the hard roof,and reduces the abutment stress.Therefore,it is advisable to prioritize the selection of the lower hard roof as the target stratum.
查看更多>>摘要：The Voronoi grain-based breakable block model(VGBBM)based on the combined finite-discrete element method(FDEM)was proposed to explicitly characterize the failure mechanism and predict the deforma-tion behavior of hard-rock mine pillars.The influence of the microscopic parameters on the macroscopic mechanical behavior was investigated using laboratory-scale models.The field-scale pillar models(width-to-height,W/H=1,2 and 3)were calibrated based on the empirically predicted stress-strain curves of Creighton mine pillars.The results indicated that as the W/H ratios increased,the VGBBM effec-tively predicted the transition from strain-softening to pseudo-ductile behavior in pillars,and explicitly captured the separated rock slabs and the V-shaped damage zones on both sides of pillars and conjugate shear bands in core zones of pillars.The volumetric strain field revealed significant compressional defor-mation in core zones of pillars.While the peak strains of W/H=1 and 2 pillars were relatively consistent,there were significant differences in the strain energy storage and release mechanism.W/H was the pri-mary factor influencing the deformation and strain energy in the pillar core.The friction coefficient of the structural plane was also an important factor affecting the pillar strength and the weakest discontinuity angle.The fracture surface was controlled by the discontinuity angle and the friction coefficient.This study demonstrated the capability of the VGBBM in predicting the strengths and deformation behavior of hard-rock pillars in deep mine design.
NETL
NSTL
万方数据