Anisotropic creep behavior of soft-hard interbedded rock masses based on 3D printing and digital imaging correlation technology

Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent properties of natural layered rock masses.In this paper,soft-hard interbedded rock masses with different dip angles were prepared based on 3D printing(3DP)sand core technology.Uniaxial compression creep tests were conducted to investigate its anisotropic creep behavior based on digital imaging correlation(DIC)technology.The results show that the anisotropic creep behavior of the 3DP soft-hard interbedded rock mass is mainly affected by the dip angles of the weak interlayer when the stress is at low levels.As the stress level increases,the effect of creep stress on its creep anisotropy increases significantly,and the dip angle is no longer the main factor.The minimum value of the long-term strength and creep failure strength always appears in the weak interlayer within 30°–60°,which explains why the failure of the layered rock mass is controlled by the weak interlayer and generally emerges at 45°.The tests results are verified by comparing with theoretical and other published studies.The feasibility of the 3DP soft-hard interbedded rock mass provides broad prospects and application values for 3DP technology in future experimental research.

Fine Characterization and Analysis of Drying Strain of the ELM Board via DIC Technology

In this paper,the occurrence and development mechanism of strain on the cross-section during the wood drying is explored.Therefore,strain regularity on the cross-section of 50 mm thickness elm(Ulmus rubra)board at the temperature of 40℃and 80℃is detected via digital image correlation technology.Hence,the difference between tangential and radial strain at surface and core layers was denoted.The results showed that strain distribution in the width direction of the board is uneven.Moreover,a large drying shrinkage strain occurs at the near-core layer,while the maximum strain difference reaches 4.08%.Hence,the surface of the board is cracked along the thickness direction.The radial strain of the board is higher than the tangential strain in the early stage of drying,while these strains are reversed in the later stage of drying.The temperature is related to the difference between the tangential and radial strains of the elm board.These differences at the core layer are larger than those of the surface layer.The conducted research results provide a theoretical basis for process optimization.

The First International Digital Printing and Image Technology Exhibition & The Sixth International Exhibition of Quick Printing Equipment & Technology

Time: Sept.4-6, 2008Venue: Shenzhen Convention & Exhibition CenterSponsor: Printing and Printing Equipment Industries Association of China (PEIAC)Organizers: The Exhibition Department of

Mechanical properties and damage characteristics of solidified body-coal combination in continuous driving and gangue backfilling

Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.

Three-Dimensional Volumetric Analysis of Venous Malformations for Assessing the Effectiveness of Percutaneous Sclerotherapy

BACKGROUND Percutaneous sclerotherapy can be used to successfully treat venous malformations(VMs)of the head,neck,and limbs.However,the standard curative effect of sclerotherapy has rarely been analyzed,and there is currently no accurate statistical method to measure the volume of VMs after sclerotherapy.Here,we propose a novel threedimensional(3D)reconstruction method to evaluate this effect.OBJECTIVE To test the feasibility of 3D software(MIMICS 19.0)to evaluate the treatment effect of sclerotherapy.METHODS This retrospective study included patients with VMs on the head,neck,and limbs who were treated with ethanol sclerotherapy or foam sclerotherapy every 8 weeks.MIMICS 19.0 was used to calculate the performance of the lesion after treatment and measure the VM volumes before and after the treatment.The effect of the clinical treatment dose on the lesion was evaluated,and the treatment effect of each patient was recorded.The relationship between the number of treatments and the reduced volume of VMs was analyzed.RESULTS Based on the MIMICS-calculated regions of interest(ROI),we found that 1 mL of ethanol reduced the lesion by 473 mm3 and that one dosage of foam(1 mL of polidocanol and 4 mL air content)reduced the lesion by 2138 mm3,demonstrating that the foam sclerosing agent exhibited greater efficacy in this study.CONCLUSIONS The MIMICS 3D volume reconstruction method can effectively and safely evaluate the efficacy of sclerotherapy and provide a preoperative evaluation.This method is simple,accurate,and feasible.