Search

• A rockmass joint generation technique considering the random distribution characteristics of geometric parameters has been established and validated. • The influence of cross-section layout and random distribution of joints parameters on the failure mechanism of deep jointed rockmass tunel are systematically analyzed. • The active deformation control method suitable for deep jointed soft-rock tunnels is proposed and applied. In order to investigate the failure mechanism of multiple parallel tunnels considering the random distribution of rockmass joints, this paper conducts in-depth study on the instability characteristics, deformation mechanism and active deformation control methods of deep jointed soft-rock tunnels. A rockmass joint generation technique considering the random distribution characteristics of geometric parameters has been established and validated. Compared to the ordinary single-hole tunnel, the failure mode of the double-hole tunnels with parallel adit is much more complex, with the deformation mainly reflected on the outer side of the left and right holes. The surrounding rock pressure is concentrated at both ends of the normal direction of the bedding plane. Narrowing the distribution range of joint dip angle will exacerbate the asymmetry of surrounding rock deformation, and a larger range of joint dip angle can make the stress characteristics of the supporting structures more uniform. Increasing the joint trace length will gradually increase the overall displacement of the surrounding rock and reduce the number of yielding blocks. As the density of joints increases, the stress in the surrounding rock becomes more uniform, but it can lead to more fractured rockmass, reduced the deformation stability, and is not beneficial for the formation of key structural layers. The active deformation control method suitable for deep jointed soft-rock tunnels is proposed and applied. Under conventional passive support schemes, the surrounding rock faces a high risk of instability collapse, with a failure probability exceeding 20%. The active deformation control concept represented by prestressed support and grouting reinforcement can effectively improve the safety factor of surrounding rock and reduce the instability probability of rockmass. For the deep stratum with developed joints, it is difficult to effectively apply high prestressing force to the internal stable structural layer. Therefore, a long-bolt with full-face grouting scheme shall be considered to actively reinforce the deep jointed rockmass. [ABSTRACT FROM AUTHOR]

How to quantitatively account for the effect of SC-CO 2 (Supercritical Carbon) rock-breaking in different rock sites is the key concern in the engineering application of non-explosive rock-breaking technology and economic comparison and there is a lack of experimental basis for relevant studies. Through the equivalent calculation of industrial emulsion explosives, a typical representative granite and mudstone site was selected, and a field experimental program was designed to compare the equivalence of the rock-breaking effects of SC-CO 2 and industrial explosives. Based on the rock-breaking equivalent field experiment, we compared and analyzed the rock-breaking area characteristics and parameter changes, such as rock-breaking volume, the morphology of the rock-breaking area, bulk rate, and unit consumption, between SC-CO 2 and industrial explosives. A correction of the equivalent conversion formula based on the volume of broken rock was realized. The study shows that SC-CO 2 breaks the rock in an elliptical volume shape, the explosives are round, the range of SC-CO 2 fracturing breaks the rock is smaller than the range of explosives breaks the rock, and the unit consumption of CO 2 is 6–10 times of the unit consumption of explosives. The rock bulk rate is higher after SC-CO 2 breaking, while the explosive blast stress wave distribution is uniform, and the bulk rate is low. SC-CO 2 rock-breaking produced by the surface vibration velocity is much smaller than the industrial explosives rock-breaking, industrial explosives blasting point of the combined vibration velocity value of the SC-CO 2 rock-breaking point of the combined vibration velocity value of 9–11 times, SC-CO 2 rock-breaking vibration impact on the surrounding environment is relatively small. The peak combined stress at the measurement point generated by SC-CO 2 rock breaking is higher than that of industrial explosives rock breaking, which is 1.2–1.6 times the corresponding measurement point value in the explosives rock breaking test. The study provides an experimental basis for research on the equivalence of SC-CO 2 rock-breaking and industrial explosives rock-breaking. • Field experiment compared rock-breaking effects of SC-CO 2 and explosives in granite and mudstone sites. • The rock-breaking area characteristics and parameter changes was compared and analyzed. • The correction of the equivalent conversion formula based on the volume of broken rock was realized. [ABSTRACT FROM AUTHOR]

High performance cementitious composites with limited carbon emission and enhanced dynamic mechanical property is prospective in developing eco-efficient concrete structures that can both sequestrate carbon and suffer impact loads especially for protection facilities. For the aim, static and dynamic mechanical properties of 2% steel fiber (wt.%), 15% silica fume (SF) and 20% fly ash microsphere (FAM) added cementitious composites with CO 2 curing treatment were explored. Spilt Hopkinson Pressure Bar testing system (SHPB) coupled with high-speed camera were adopted, carbonation-hydration kinetics in the process of CO 2 curing treatment was also focused using a modified isothermal calorimetry method. It was found that carbonated high performance cementitious composites of C-8 showed the highest 1-d and 56-d static compressive strengths, correspondingly with 63.4 MPa and 114.7 MPa, its dynamic compressive strength increased with strain rates, almost reached to 120 MPa at 111 s−1. Drastic carbonation heat flow with peak value of 0.044 W/g and a normally subsequent hydration process were innovatively revealed in the high performance cementitious composites. [Display omitted] • Carbonation treated HPCC showed an obvious enhancement both for 1-d and 56-d static compressive strengths. • Dynamic compressive strength of HPCC was significantly strain-rate dependent and incrased to 120 MPa at 111−1. • An obvious carbonation heat flow followed by a subsequent hydration process was observed in HPCC. [ABSTRACT FROM AUTHOR]

As a prospective clean alternative energy, the application of hydrogen increases. This study investigates the explosion characteristics of vol. 0%–50% hydrogen proportion in hydrogen enriched compressed natural gas (HCNG) within a 0.5 × 0.5 × 0.5 m3 square vessel and assesses the effect of HFC-227ea/CO 2 as the explosion suppressant. Results show that with an increase in proportion of hydrogen in mixture, the explosion characteristic parameters of HCNG transit towards hazard enhancement. Subsequently, the explosion suppression experiments are carried out using CO 2 , HFC-227ea or blends of two suppressants. It is proved that the explosion pressure and flame speed are significantly reduced by the volumetric concentration of inhibitor. The stretching behavior of flame surface under effect of inhibitors are recorded. The concentrations for complete inhibition are vol. 14% for CO 2 and vol. 8% for HFC-227ea respectively. The inhibitory effect of HFC-227ea is significantly better than that of CO 2 which is explained by physical (oxygen dilution and heat absorption) and chemical properties (thermal decomposition and chain reaction attenuation) of both suppressants. Finally, the collaboration effect of two inhibitors on explosion suppression is examined, finding that at vol. 4% HFC-227ea, the two suppressants exhibit a positive synergistic effect on explosion mitigation. • The explosion of HCNG transits towards the hazard enhancement. • Explosion pressure and flame speed are reduced by both suppressants. • The inhibitory effect of HFC-227ea is significantly better than that of CO 2. • Blended suppressants have a synergistic effect on explosion mitigation at vol. 4% HFC-227ea. [ABSTRACT FROM AUTHOR]

Due to wide flammability limit and low ignition energy, the explosion risk of hydrogen enriched compressed natural gas (HCNG) is augmented by the hydrogen proportion. The paper aims to evaluate the synergetic suppression performance of ABC powder/potassium bicarbonate-zeolite (PBZ) composite powder and HFC-227ea/CO 2 on HCNG explosion. The suppression experiments on 20% and 50% hydrogen ratios are conducted in a 0.5 m-long cubic container. For X H 2 = 20% HCNG explosion, with addition of optimal concentration of PBZ composite powder (0.1 g/L), the explosion overpressure decreases from 137 kPa at vol. 2% CO 2 to 133 kPa at vol. 1% HFC-227ea. Thus, the inhibitor effect of HFC-227ea is superior to that of CO 2. For both X H 2 = 20% and 50% HCNG explosions under optimal concentrations of PBZ composite powder or ABC powder, the critical values of positive and negative synergetic effects under CO 2 or HFC-227ea inert gas suppressions are revealed. The positive synergetic suppression effect generally occurs at low hydrogen doping ratio and low suppressant concentration. Increase of suppressant concentration leads to a decline in reaction temperature, causing that the powder cannot be decomposed completely and the chemical inhibition effect is weakened. • Suppression performance of ABC or PBZ composite powder is revealed. • Suppression effect of ABC powder and PBZ composite powder is compared. • Positive and negative critical collaboration by CO 2 and HFC-227ea is revealed. • The combined suppressing mechanism of gas-solid suppressant is analyzed. [ABSTRACT FROM AUTHOR]

• Response characteristics of HDPE pipe is obtained by field test. • LS-DYNA is utilized to simulate the jointed pipe under blasting load. • Contrast analysis of the effect of a joint on the dynamic behavior of the pipe. • Mechanical properties of jointed HDPE pipe under complex blasting conditions. • Predicting pipe response under complex conditions using an optimized ELM model. The reliability of buried jointed high-density polyethylene (HDPE) corrugated pipelines under urban blast vibration loading needs to be emphasized. This study combines field blasting tests on directly buried single-section pipelines and numerical simulations to investigate the mechanical performance of jointed HDPE corrugated pipelines under complex blasting conditions. Intelligent prediction models based on genetic algorithm (GA), particle swarm optimization (PSO), and white shark optimization (WSO) combined with extreme learning machine (ELM) are proposed, namely GA-ELM, PSO-ELM, and WSO-ELM models, respectively. The numerical model is established using the orthogonal experimental principle to supplement the predicted sample data. By comparing the predictions of RPPV (resultant peak particle velocity) and RPPD (resultant peak particle displacement) for the pipelines under various working conditions using the four optimized ELM models, the results indicate that the WSO-ELM model is the best intelligent model for predicting the pipeline response characteristics. By combining the pipeline deflection criterion with the WSO-ELM prediction model, adjustments to the field blast parameters can be made to ensure the safety of the pipeline while improving construction efficiency. [ABSTRACT FROM AUTHOR]

For large quantities of hydrogen transportation, it is a potential solution for mixing a certain proportion of hydrogen into natural gas pipeline network. In is imperative to seek efficient explosion suppressants of hydrogen enriched compressed natural gas (HCNG). In current work, a 125 L cubic explosion container was developed to conduct the suppression experiments on 20% and 50% HCNG explosion using inhibitory solids of 0.04–0.32 g/L ABC powder and 0.04–0.16 g/L potassium bicarbonate-zeolite (PBZ) composite powder. The thermodynamic and particle size properties of ABC powder and PBZ composite powder were analyzed to interpret these suppression effects. The pressure history curve and explosion flame appearance were recorded. The flame exhibited a deformation and wrinkles characteristic when the solid suppressants were employed. The optimal concentrations of ABC powder and PBZ composite powder suppression were attained. The physical and chemical mechanisms of explosion mitigation with ABC powder or PBZ composite powder were fully revealed. The single inhibitory powder of ABC powder or PBZ composite powder could not fully restrict the HCNG explosion. The current results possessed some practical guidance for restriction of HCNG explosion in industrial confined spaces. • Powder suppressions on 20% and 50% HCNG explosion are conducted. • Flame shows a deformation and wrinkles shape under inhibitory powders. • The inhibitory effect of PBZ composite powder is than that of ABC powder. • Optimal concentrations of ABC powder and PBZ composite powder are attained. [ABSTRACT FROM AUTHOR]

• The numerical model of the layered surrounding rock tunnels under dynamic and static loads was established. • A prediction model for the stress and displacement of surrounding rock considering geostress factors is proposed. Ensuring the safe excavation of layered surrounding rock tunnels requires a comprehension of the dynamic response characteristics and instability mechanism of the rock under dynamic and static loads. The impact of variations in geostress on tunnel stability is a concern that cannot be disregarded as long-distance tunnel construction continues to grow. This paper provides a detailed description of the maximum principal stress dynamic response and deformation characteristics of the tunnel's layered surrounding rock with the change of geostress under dynamic and static loads using model tests and numerical simulation methods. The effects of different loads, different geostress, different locations, and different failure modes on the maximum principal stress and displacement of the tunnel's layered surrounding rock are comparatively analyzed. A prediction model of the maximum principal stress and maximum displacement of the layered surrounding rock affected by geostress under the dynamic load is proposed by dimensional analysis. At last, based on the prediction model, the critical lateral pressure coefficient was obtained to be 0.74 and the maximum displacement of 12.98 mm appears at the left spandrel when the tunnel depth reaches the maximum of 963 m. [ABSTRACT FROM AUTHOR]

• The "explosive cladding window" of Monel alloy/Cu bimetallic bonded rod was calculated and designed. • Monel alloy/Cu explosive cladded rod with wavy interfaces was prepared using the preferred cladding parameters. • The interfacial bonded strength was superior to that of Cu matrix. • There are molten zone (amorphous as well as nanosized Ni 3 Si phases), heat-affected zone (recrystallized grains), and deformation zone (microbands) in the interface bonded region of the Monel alloy/Cu explosive cladded rod. Explosive cladding parameters directly affect the interfacial bonded quality, and they are crucial for choosing appropriate cladding parameters for different metal combinations. The "explosive cladding window" of Monel alloy/Cu bimetallic bonded rod was designed utilizing MATLAB software, and the Monel alloy/Cu explosive cladded rod with wavy interfaces was successfully fabricated by applying optimal cladding parameters. On this basis, the interfacial microstructure and mechanical properties of Monel alloy/Cu explosive cladded rod were investigated. The TEM results showed that the interface bonded region consists of three parts: the molten zone (amorphous, nanosized Ni 3 Si phases), the heat-affected zone (recrystallized grains), and the deformation zone (microbands). Deformation twins were present in the matrixes of Monel alloy and Cu. The number, morphology, and distribution of deformed twins on the two sides are different due to the different stacking fault energies of Monel alloy and Cu. Compression-shear separation tests revealed that the fracture occurred on the Cu side, indicating the interfacial bonded strength is higher than that of the Cu matrix. In addition, the interfacial hardness was lower than on the Monel alloy side but higher than on the Cu side, which is associated with severe deformation and recrystallization near the interface. This work provides a method combining theoretical design and experimental research for choosing the process parameters of bimetallic rods, which provides an important reference for optimizing explosive cladding parameters of heterogeneous metal and facilitates the wide application of explosive cladding techniques. The Monel alloy/Cu explosive cladded rod with wavy interfaces was successfully fabricated by applying optimal cladding parameters. The interface bonded region of Monel alloy/Cu explosive cladded rod is mainly composed of three parts: (1) molten zone, including amorphous and nanosized Ni 3 Si phases; (2) heat-affected zone, consisting of recrystallized equiaxed grains and abnormally grown grains; (3) deformation zone, consisting of microbands. [Display omitted] [ABSTRACT FROM AUTHOR]

Steel fiber reinforced concrete (SFRC) has been widely used in protective engineering, traffic engineering and many other fields. However, there is no unified conclusion about the combined effect of concrete matrix strength, steel fiber content, and strain rate on the spalling strength of SFRC under dynamic load. For this purpose, 9 types of SFRC with different matrix strengths (C45, C60, C80) and steel fiber volume contents (0%, 2%, 4%) were tested in the strain rate range of 2 × 1 0 − 5 ∽ 18. 9 s − 1 through static direct tensile test and dynamic spalling test using the Hopkinson pressure bar (HPB). Accordingly, an improved Holmquist–Johnson–Cook (HJC) model of SFRC was proposed by introducing a fiber increase factor (FIF) and a dynamic increase factor (DIF) to modify the strength criterion at the compressive and tensile phases. Furthermore, the improved HJC model was embedded into ABAQUS/Explicit code for numerical simulation. The simulated spalling failure agrees with the testing result, indicating the rationality and feasibility of the proposed model for characterizing the dynamic spalling behavior of SFRC. • Dynamic spalling test on steel fiber reinforced concrete (SFRC) are conducted. • Effect of matrix strength, steel fiber content, and strain rate are discussed. • Improved HJC model for SFRC is proposed, which suitability is verified. [ABSTRACT FROM AUTHOR]

[Display omitted] • A strategy for flexible, efficient and programmable crashworthiness based on plastic deformation of metals was proposed. • The feasibility of modular self-locked, perforated and nested designs was demonstrated by experiments and simulations. • The perforating optimization was carried out to induce efficient deformation mode and obtain desirable crashworthiness. • The step functions were created on stress curve by nested design to induce programmable crash performance. Cellular materials and mechanical metamaterials respectively display desirable efficiency and programmability in engineering protection, however, the means to combine their advantages poses a challenge. To break this limit, a universal strategy based on plastic deformation of metals is established to realize flexible, efficient and programmable crashworthiness, which is implemented in three steps. Firstly, cellular material is discretized as multiple self-locked tubes, endowing it with convenient assembling and disassembling processes as well as flexible property tunability to adapt to load characteristics. Then, perforated design is executed mainly to induce efficient progressive buckling mode and superior crashworthiness by creating geometry discontinuities. Finally, nested design is employed to promote space utilization and plateau stress. More critically, multiple step functions with target characteristics can be introduced on stress–strain curve to obtain programmability by controlling parameters of fillers. The windmill-inspired system made of 316L stainless steel is taken as the instance to implement the strategy, and both quasi-static and dynamic loading conditions are considered. The strategic feasibility is validated by experiments and simulations, and specific energy absorption, energy absorption efficiency and force efficiency respectively increase by 53.8%, 13.5% and 77.9%. This research opens a new avenue for combing efficient mechanical behavior and flexible property programmability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Field explosion tests of the full-scale buried pipeline were carried out. • Safety control standard of peak particle velocity (PPV) of pipeline was proposed. • Dynamic response of pipeline with different buried depth were discussed. • Evaluation of pipeline considering buried depth and blasting vibration was studied. In order to effectively control the damage of blasting construction to the upper pipeline, it is necessary to reveal the impact of blasting vibration on the pipeline. By conducting an on-site crossing blast experiment under the pre-buried full-scale gas pipeline, the vibration distribution characteristics of pipeline and ground surface soil in the process of blast crossing the upper gas pipeline were analyzed based on field blasting vibration monitoring and dynamic strain test. Combined with the results of dynamic strain analysis of pipeline in field test, the safety control standard of peak particle velocity (PPV) of the pipeline was proposed based on the allowable strain criterion of the pipeline. Moreover, a 3D numerical model was established to analyze the response characteristics of upper buried gas pipeline subjected to blasting vibration and its reliability was verified using the field monitoring data. Considering the influence of pipeline burial depth, the numerical calculation experiments were carried out, and the dynamic response characteristics of pipelines subject to blasting vibration under different buried depth conditions in urban areas were discussed. At last, the functional relationships between the PPV of pipeline and the PPV of ground surface soil above the pipeline, the peak effective stress (PES) of the pipeline and the PPV of ground surface soil were established, and the safety control and evaluation of the pipeline considering the buried depth under the influence of blasting vibration could be realized. [ABSTRACT FROM AUTHOR]

• Full scale field surface explosion experiment is conducted. • The reliability of the numerical model and parameters are proved by field tests. • The controlled explosive charge on the surface above the pipeline is obtained. To ensure the safety of the underground gas pipeline in urban ground explosion construction and terrorist attack, a study of the safety of buried gas pipelines under surface explosions is inevitable. In this paper, an operating gas pipeline in Wuhan Economic Development Zone is taken as an example, and the surface explosion full-scale experiment is carried out in the open site. In the field experiment, small charge of No. 2 rock emulsion explosives were used to simulate ground construction blasting, the blasting vibration velocity tester (TC-4850) and dynamic strain measurement system (DH5956) are used to monitor data, the analysis of field data shows that the experimental data meet the general rules, which proves the reliability of the field experiment. Secondly, the numerical model of pipeline response characteristics under surface explosion is established, and the reliability of the model is verified by field monitoring data. In the numerical analysis, the operating pressure of 0.2 MPa is given to the pipeline following the actual working condition, and the response characteristics of the pipeline under the condition of large explosive charge blasting on the surface are discussed. Based on the simulation results, the dangerous section and dangerous point of the pipeline under the action of ground explosion are analyzed, and the functional relationship between the peak effective stress (PES) of pipeline dangerous point and the explosive charge on the surface is deduced. Finally, according to the pipeline control value of PES determined in relevant specifications, the controlled explosive charge of surface construction blasting is obtained. Further, the equivalent conversion analysis of No. 2 rock emulsion explosive and TNT explosive is carried out, and the TNT controlled explosive charge of ground terrorist attack is obtained. [ABSTRACT FROM AUTHOR]

• Investigated the features of stress transients of RC columns of demolished high-rising buildings. • A 1000 mm × 700 mm × 4100 mm column was blasted in a 56-m-high frame structure. • Strain time histories and the failure mode of the column were collected as data. • A concept model to detailly describe the stress transient of blasted RC columns is proposed. Blasting demolition is the preferred method for safely and efficiently demolishing high-rise buildings, and numerical simulation is very helpful for the design of complicated blasting schemes. In simulations of demolition projects, the explosion processes and blast loadings are usually ignored to save computer time. However, the stress transients of blasted columns at the bottom of buildings are important boundary conditions, which may affect the accuracy of simulation results. Yet, few works have investigated it and provided a detailed model. To investigate the features of stress transients of reinforced concrete (RC) columns, an experiment was conducted in the present study. In a 56-m-high frame structure demolished by controlled blasting technology, a 1000 mm × 700 mm × 4100 mm column was blasted. The collected data include strain-time histories and failure mode of the column. The study shows that explosion-induced stress-time history curves far from the blastholes are jagged-triangular, which may have multiple peaks because of the delay time errors of detonators. After detonation of explosives, the bearing capacity of the column gradually decreases, which takes several milliseconds. When the bearing capacity reduces to less than the initial axial compressive stress in the column, the initial stress releases linearly, which also takes several milliseconds. The movements of the concrete fragments bent the longitudinal reinforcement bars, which induces a strong tensile stress in the residual column; their stress-time history curves are triangular. Based on the experiment results, a stress transient concept model is proposed to detailly describe the stress state of blasted RC columns in demolished high-rising buildings, which can be applied in the numerical simulation of demolition blasting. [ABSTRACT FROM AUTHOR]

• A comprehensive identification method for the surrounding rock stability of soft-rock tunnels under rapid construction was proposed to determine the overall safety factor within the instability track. • The comprehensive identification method can determine whether the surrounding rock has experienced sliding instability along the yield surface or loose and fractured instability. • The stability deterioration mechanism of surrounding rock for soft-rock tunnels accompanied by extrusion deformation under long-footage rapid construction has been revealed. Faced with the increasing development trend of extra-long traffic tunnels in western China, adopting the long-footage rapid construction method in soft-rock strata is the key to improving construction efficiency. Therefore, exploring the method for the stability identification of soft-rock tunnels suitable for long-footage rapid construction is of great practical engineering significance. A comprehensive identification method for the surrounding rock stability of soft-rock tunnels under rapid construction was proposed by combining the upper-bound limit analysis method and the safety factor method. This method was applied to analyze the progressive deterioration mechanism of surrounding rock stability under different geological environments and excavation footages. Finally, based on the tunnel engineering that crosses the carbonaceous slate stratum, the physical and mechanical parameters of the surrounding rock were calibrated by monitoring the mechanical behavior of the support structure. Moreover, the applicability of this method in engineering practice was analyzed. The results show that the safety factor expressed by the ratio of dissipated power to external force power can form a one-to-one mapping relationship between the instability trace and the safety factor. Thereby, the correlation equation between the safety factor and the in-situ stress is established. The proposed comprehensive identification method can determine whether the surrounding rock has experienced sliding instability along the yield surface and whether it has experienced collapse caused by overall loose and fractured instability. After adopting the long-footage rapid construction method and strengthening the support structure, the haunch convergence only increases by 11.1%, and the vault settlement decreases by 9.3%. These data verify the engineering applicability of this method. [ABSTRACT FROM AUTHOR]

• The CEEMDAN-PE-HE-SWT method is proposed to denoise the carbon dioxide blast wave signal. • Dividing IMFs into three types using permutation entropy and Hurst exponent. • Applying the stationary wavelet transform to remove the noise in the mixed IMFs. • The purity of simulated and measured carbon dioxide blast wave signals is effectively improved. Monitoring the carbon dioxide blast wave is an efficient method for determining the power of carbon dioxide blasting. Due to the harsh measurement environment, noise is inevitably mixed into the recorded signals. This work proposed a hybrid denoising strategy based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), permutation entropy (PE), Hurst exponent (HE), and stationary wavelet transform (SWT). Firstly, the measured signal is decomposed by CEEMDAN, and then multiple intrinsic mode functions (IMFs) are divided into pure, mixed, and noisy by PE and HE. The noise in the mixed IMFs is removed by SWT. Finally, the blast wave is reconstructed through the pure and denoised mixed IMFs. The denoising performance of the proposed approach was compared with that of the other six approaches. The results indicate that the proposed approach has better performance and could be regarded as an effective denoising method for carbon dioxide blast waves. [ABSTRACT FROM AUTHOR]

• Numerical simulation software was used to establish the numerical model of the ancient pagoda under the blasting load of the underpass tunnel. • The maximum primary stress and vibration velocity were analyzed by numerical modeling in order to safeguard historic structures. • The reason why the vibration velocity and stress of each part of irregular tower vary greatly is analyzed. • The safety of the ancient pagoda is assessed according to the relevant norms. In the blasting excavation project of the subway tunnel in the urban area, ensuring the safety of the surface buildings (structures) above the crossing area is the key concern. This paper is based on the blasting project of the ancient pagoda (Shengxiang Pagoda) under the tunnel between Pengliuyang Road Station and Simenkou Station of Wuhan Metro Line 5. To protect the integrity of the ancient buildings, this paper mainly adopts the numerical simulation method to analyze the dynamic response characteristics of the tower above the subway and realizes the safety assessment of the tower based on the maximum principal stress and vibration velocity control. The results show that the maximum error rate between the measured data and the numerical simulation results is only 11.9 %, which verifies the reliability of the numerical model and parameters. In the process of blasting vibration propagation, the vibration velocity of the tower body is affected by the whiplash effect and the elevation amplification effect. The vibration velocity of the tower bottom is 0.29 cm / s, and the vibration velocity of the tower tip reaches 4.29 cm / s. The vibration velocity of the upper part of the tower is much larger than that of the lower part. The stress distribution of the tower body is accompanied by stress concentration, with the maximum reaching 0.0442 MPa and the minimum only 0.014 MPa. The safety assessment of the ancient pagoda from the aspects of structural strength and vibration velocity can determine that the structure is safe under this condition. The research results are of great significance to the analysis of dynamic response characteristics and safety evaluation of ancient buildings under blasting load in urban complex environments. [ABSTRACT FROM AUTHOR]

The liquefaction in saturated sands under blast loading is an important research topic in geotechnical engineering. The effect of blast loading on the liquefaction characteristics of saturated sands was studied through a large-scale millisecond delay blasting (MDB) liquefaction field test. Based on the field test, a numerical model was established by the LS-DYNA finite element program to study the propagation of blast waves and the effects of explosive mass, scaled distance, and blast delay on the liquefaction characteristics of saturated sands. The results show that there was a significant sand boiling phenomenon in saturated sands under blast loading, and high values of the excess pore water pressure ratio were observed at monitoring points during the field test. The numerical simulation results show that the scaled distance and the blast delay significantly affected the excess pore water pressure. While the blast delay increased from 110 ms to 330 ms, the excess pore water pressure of the central area can increase by more than 18%. Based on the field and numerical tests, an empirical equation is established that can take into account both the scaled distance and blast delay, which provides a theoretical basis for future large-scale liquefaction sites by MDB. • Liquefaction and sand boiling in saturated sands by millisecond delay blasting (MDB) was observed. • Based on field test, the effects of explosive mass and blast delay on liquefaction were investigated by LS-DYNA. • The empirical equation of the liquefaction caused by MDB was established. [ABSTRACT FROM AUTHOR]

Accelerated carbonation of cement and concrete at early age is an essential technique for both of carbon sequestration and performance improvement, while the core carbonation heat and the interplay with the subsequent hydration process remain unclear. This study aims to develop a method to explore carbonation-hydration heat evolution using a modified isothermal calorimeter, microstructure characterization of carbonated pastes was revealed by multi-techniques of TG/DTG, XRD, SEM and thermodynamic modelling. Carbonation heat was confirmed and the intensity of this heat was much higher than that of hydration heat. Interestingly, the main hydration peak flow overlapped with the front carbonation flow, while three factors including prior-hydration time, w/c ratio and superplasticizer (SP) were found to be the key factors to obtaining independent carbonation-hydration flow in this process. Furthermore, prior-hydration of 2 h promoted CO 2 uptake of paste to 14.9%, and the generation of 1–4 μm calcium carbonate crystals with irregular graininess and rhombohedral-like shape were also observed in carbonated pastes. • Intense carbonation heat in pastes was confirmed based on the proposed method using a modified isothermal calorimeter. • Pre-hydration time, w/c ratio and superplasticizer were found critical to reveal independent carbonation-hydration kinetics. • Irregular graininess and prism-like crystals of calcium carbonates with 1–4 μm were observed in carbonated cement paste. • The calculated phase assemblage predicted the generation of calcite, C–S–H and portlandite with different hydration ages. [ABSTRACT FROM AUTHOR]

• Propagation characteristics of the pipe under blasting vibration are summarized. • Analysis of the dynamic failure modes and safety criteria of pipes is conducted. • Safety criteria of the pipe obtained from the existing literature are summarized. • The frontiers and priorities of the subsequent research are described. With the development of urban underground space engineering, urban shallow buried pipelines are confronted with great threats of blasting vibration induced by the vast underground blasting excavation projects. The study of vibration effects on buried pipelines adjacent to blasting excavation and the related blasting safety control standards are hot issues in the field of pipeline engineering and blasting engineering in recent years. Firstly, based on the existing research and developments of the blasting vibration effect on buried pipelines, the characteristics and propagation characteristics of the buried pipeline under blasting vibration are summarized from a field test, indoor law of blasting vibration load of the pipeline are introduced. Then, the literature on the study of the dynamic response law of pipelines using field tests, outdoor tests and numerical simulations is analyzed. Next, a comprehensive analysis of the dynamic failure modes and safety criteria of buried pipelines is conducted based on the study of the dynamic response characteristics of pipelines. Moreover, the blasting vibration safety criteria of the pipeline obtained from the existing literature are summarized. Finally, the disadvantages of the current research on pipeline blasting vibration effects are indicated, and the frontiers and priorities of the subsequent research are described. [ABSTRACT FROM AUTHOR]

• A new folding implosion method for demolishing high-rise RC buildings is developed. • Some design criteria for the folding implosion method are proposed. • The folding implosion method expands and supplements the building implosion technology. Blasting is an efficient method for demolishing high-rise buildings and structures. If the collapse scope of a building to be blasted is insufficient controlled building implosion technology is preferred. However, for the conventional implosion, there is a lot of pre-weakening work that has to be done, and it is almost impossible to demolish the high-rise thin wall structures such as reinforced concrete (RC) chimneys. Therefore, a folding implosion method is proposed. In this method, several wedge-shaped notches should be blasted out in the high-rise building or structure, then these notches will turn to "plastic hinges", meanwhile, the building or structure will turn to a folding kinematic chain, and the segments will overlap each other after falling down. For this method, some design criteria for the main parameters such as the position, initiation sequence, and initiation time delay of blast notches are proposed. The multi-body dynamics models for bi-folding implosion and tri-folding implosion are deduced to analyze the folding motions and rationality of the blasting plans. In two implosion cases, the design criteria and kinematics models are validated. [ABSTRACT FROM AUTHOR]