Research on the Dynamic Evolution Mechanism of Soil Arching in Curve Shield Tunneling Based on Asymmetric Strata Loss

To investigate the influence of fissure spacing on the dynamic mechanical properties of rock, split Hopkinson pressure bar (SHPB) impact tests were conducted. The rock fracture process was fully recorded using a high-speed camera, and the dynamic fracture behavior and failure mechanisms of rocks containing non-persistent fissures with different spacing were systematically studied. The results show that as the fissure spacing increases, the peak strength and Young’s modulus of the specimens gradually decrease, and brittleness is enhanced. The energy absorption process can be divided into three stages: elastic energy storage, damage propagation, and structural failure, with the transition points corresponding to the yield point and the instability critical point on the stress-time curve, respectively. The energy utilization efficiency of fissured specimens is significantly lower than that of intact specimens, and it first decreases and then increases with increasing fissure spacing, reaching a minimum at a spacing of 15 mm and approaching the level of intact specimens at 30 mm. The failure mode shifts from tensile-dominated persistent cracking to shear-dominated mixed failure as spacing increases, and eventually tends to a disordered, network-like cracking pattern. A critical spacing threshold exists; beyond this threshold, end-face effects become dominant and the persistent interaction between fissures weakens. This study systematically reveals the influence of fissure spacing on the dynamic mechanical behavior and failure mechanisms of rock masses, provides a reference for evaluating the dynamic stability of fissured rock masses, and offers an important basis for further understanding the dynamic mechanical response mechanisms of fractured rock.

Dynamic mechanical characteristic and fracture evolution mechanism of deep roadway sandstone containing weakly filled joints with various angles

Volatile organic compound (VOC) emissions from pyrolysis of widely used biomass are expected to increase significantly under the carbon neutrality target. However, the dynamic emissions and evolution mechanism of biomass-VOCs remain unclear, hindered by complex reactions and offline measurements. Here, we propose a novel covariant evolution mechanism to interpret the emission heterogeneities, sequential temperature responses, and evolved correlations of both VOCs and residual functional groups (RFGs) during corn straw (CS), wood pellet (WP), and semibituminous coal (SBC) pyrolysis. An innovative combination of online thermogravimetric-Fourier transform infrared-gas chromatography/mass spectrometry and two dimensional-correlation spectroscopy was applied. The relative percentages of CS/WP-VOCs were higher than those of SBC-VOCs, and most VOCs tended to have relatively small carbon skeletons as the average carbon oxidation state increased. With the temperature increased from low to high during CS/WP pyrolysis, the primary sequential response of VOCs (acids → phenols/esters → alcohols/ethers/aldehydes/ketones → hydrocarbons/aromatics) corresponded to the RFG response (hydroxyl groups → -CH3/-CH2-/-CH groups → aliphatic ethers and conjugated ketones). Compared with the relative regularity for CS/WP responses, the gas-solid products from SBC pyrolysis exhibited complex temperature-dependent responses and high oxidation-induced variability. These insights provide favorable strategies for the online monitoring system to facilitate priority removal of coal and biomass fuels-VOCs.

Evolution mechanism of active soil arching in a shallow trapdoor under eccentric loading

To study the dynamic mechanical properties and damage evolution mechanism of Beishan deep granite under medium and high strain rates, dynamic mechanical tests for the deep granite specimens with different strain rates were conducted using the split Hopkinson pressure bar (SHPB) device. The improved Zhu-Wang-ang (ZWT) dynamic constitutive model was established, and the relationship between strain rate and strain energy was investigated. The test results show that the strain rate in the dynamic load test is closer to the strain rate in the rock blasting state when the uniaxial SHPB test is applied to the granite specimens in a low ground stress state. Peak stress has a linear correlation with strain rate, and the dynamic deformation modulus of the Beishan granite is 152.58 GPa. The dissipation energy per unit volume and the energy ratio increase along with the strain rate, whereas the dissipation energy per unit volume increases exponentially along with the strain rate. There is a consistent relationship between the damage degree of granite specimens and the dissipation energy per unit volume, which correspond to one another, but there is no one-to-one correspondence between the damage degree of granite specimens and the strain rate. To consider the damage and obtain the damage discount factor for the principal structure model, the principal structure of the element combination model was improved and simplified using the ZWT dynamic constitutive model. The change of damage parameters with strain rate and strain was obtained, and the dynamic damage evolution equation of Beishan granite was established by considering the damage threshold.

ABSTRACTThis paper investigates the mechanical properties and micro‐fracture activities of marble at depth (short for deep marble) through true triaxial dynamic tests and continuous‐discrete coupling simulations. First, the true triaxial split‐Hopkinson pressure bar (SHPB) tests were conducted to measure the dynamic mechanical properties of marble specimens. Then, a continuous‐discrete coupling model was established based on the triaxial simplified grain‐based model and the application of force–velocity transfer channel to the coupling interface. Finally, the established continuous‐discrete coupling model was calibrated against test data and used to further analyze the damage mechanical behaviors of the specimens. The results show that the peak stress, maximum strain, strain rate, damage of the specimens, and maximum electrical signals of the lateral pressure bars all increase as the impact velocity increases. The strain rate effect is noteworthy. The dynamic mechanical responses and damage characteristics of the specimens under different lateral stresses show a unique ratio of lateral stress to axial stress (RLAS) effect. With the increase of RLAS, the dynamic peak stress first increases and then decreases, while the maximum deformation capacity of the specimens changes inversely. The relatively high confining pressure can make the interior of the specimens denser, improve energy transfer efficiency, and reduce energy loss. With the increase of RLAS, the damage degree of the specimen first increases and then decreases. As the impact load increases, the dissipated energy increases and the damage degree of the specimens becomes more severe. These numerical simulation results can better explain the strain rate effect and the RLAS effect.

Dynamic fracture behaviour and evolution mechanism of soft coal with different porosities and water contents

With the increasingly fierce market competition, customers’ needs are gradually becoming more complicated, specialized, customized, and personalized. How manufacturing enterprises adopt innovation strategies to achieve value-added products as well as value co-creation with customers is an important initiative for enterprises to maintain differentiated advantages in market competition. Therefore, the creation of service value has gradually become more and more important. The related research on manufacturing servitization has attracted extensive attention in recent years. Manufacturing servitization is the evolution process of manufacturing enterprises gradually from product-dominant logic to service-dominant logic. The purpose of this study is to explore the dynamic evolution of manufacturing servitization from the perspective of innovation strategy and analyze the dynamic evolution mechanism. This study shows the latest research progress of theories related to manufacturing servitization and lays the theoretical foundation for research on the mechanism of the dynamic evolution of manufacturing servitization. This study proposes a three-stage dynamic evolution model of manufacturing servitization: product production, technological innovation, and service innovation. This study primarily employs the research methods of model construction and computer simulation. Based on the Nelson–Winter model, this study establishes a decision model for manufacturing servitization innovation strategy. This study conducts a computer simulation study on the dynamic evolution of manufacturing servitization from the perspective of innovation strategy and draws conclusions. This study is of great significance for manufacturing enterprises in making appropriate service-oriented innovation strategy decisions in the context of the service-oriented transformation occurring widely in the manufacturing industry.

Link prediction has attracted considerable attention. Empiricism and the evolution mechanism based approach are the mainstream methods for link prediction. However, one drawback of such approaches is that they usually ignore the dynamic evolution mechanism of social networks, yet being dynamic is an essential characteristic of a social network that exists in every stage of the networks evolution. In this paper, we address the problem of temporal link prediction and investigate social networks from the time dimension with the purpose of dynamic evolution mechanism capturing. First, we separate a temporal network into a series of snapshots. Then, we propose a triad transition matrix prediction algorithm to learn the change of the distribution of triads among the different snapshots. The learned changes in the distribution of triads can capture the dynamic evolution of the network. With a proposed triad transition influence quantification algorithm, we propose a motifs based link prediction method for temporal link prediction. The proposed method can capture the dynamic evolution of temporal networks and is universal than existing methods. Extensive experiments on disparate real-world networks and model networks with controllable evolution demonstrate the effectiveness of the proposed method.

Purpose The advent of the new retail era witnessed the consumers’ demand shift from on the traditional product quality to on the full supply chain service quality, and product service and service manufacturing is gradually taking shape. The purpose of this paper is to propose whether there is a “quality bridge” in the dynamic evolution process of retail service supply chain (RSSC) and discuss the system role, steady-state characteristics and dynamic evolution mechanism of service quality in this dynamic evolution process. Design/methodology/approach This paper proposes the dissipation system structure of the RSSC under the steady-state quality constraint, constructs a Markov chain model (MCM) for the evolution of the service quality of RSSC, and tests the objective existence of the steady-state distribution of the service quality by taking Chinese HJ retail enterprises as samples. Findings The research value of this study is summarized as follows. The research finds that the evolution of service quality of RSSC is a dynamic and non-linear growth process, which has significant characteristics of complex adaptability and steady-state convergence. The study finds that the quality evolution process of the RSSC is a steady-state convergence process, and there is a steady-state distribution of quality in its co-evolution, in which different process input levels have a significant positive impact on the stable level of quality state. The study finds that the steady state of quality plays a crucial role in the collaborative evolution of the RSSC, that is, when the service quality reaches a certain steady state distribution, the operating efficiency and profit level of the whole chain will show an “explosive” growth trend. Originality/value Quality bridge, an original concept in this paper, represents the role of quality steady-state in the operation of RSSC. Based on Markov chain and system simulation tools, this paper verifies the existence of steady-state service quality and its positive effect on the co-evolution and sustainable development of RSSC. When the service quality reaches a certain steady distribution, the operating efficiency and income level of the whole chain will show n trend of explosive growth.

Revealing the failure mechanisms of lithium-ion batteries during dynamic overcharge

The presence of soft soil located along the coastal belt of Australia poses a serious challenge to the construction of infrastructure projects. The pile-supported embankments provide a viable alternative to deal with such problematic soil. The soil arching mechanism plays a key role in transferring loads to piles in an efficient manner. In this study, a simplified two-dimensional finite element approach is used to demonstrate soil-arching mechanism in a granular embankment supported by piles. The influence of the piled-embankment properties such as elastic modulus of pile, friction angle and modulus of embankment-fill are investigated on the soil arching in term of stress concentration ratio. It is found that the pile and embankment modulli and friction angle significantly affects the arching mechanism. The thickness of arching zone is found to maximum at the mid of subsoil whereas minimum on the pile head and is analogous to the multi-shell theory. The effect of embankment height and pile spacing have also been reported.

Dynamic microstructural evolution and recrystallization mechanism during hot deformation of intermetallic-hardened duplex lightweight steel

Wang, Q.; Zhan, Q.; Wang, L.; Zhan, C.; Cui, B.; Liu, X.; Li, X.; Wang, X.; Yu, X., and Zhang, J., 2020. Morphodynamic evolution of the Huaihe River estuary during the Huanghe River invasion from 1128 AD to 1855 AD. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 250–256. Coconut Creek (Florida), ISSN 0749-0208.Based on historical records, we investigated the dynamic conditions, geomorphological characteristics, and evolution mechanisms of the Huaihe River estuary during the period of Yellow River invasion. The results showed that the runoff and sediment discharge of the Huaihe River increased owing to a large quantity of sediment-laden runoff into the Yellow River from 1128 to 1855 CE. However, the sediment discharge in different periods is also affected by repeated siltation along the lower reaches of the Yellow River. Huaihe estuary is a tidal estuary with moderate intensity. Its reciprocating tidal current and coastal current system are favorable to the discharge of sediment into the sea. The shape of the Huaihe estuary is narrow on the upper side and wide on the lower side. Large-scale sandbar and underwater delta were developed in the inside and outside of the estuary, respectively. The channel of the estuary has a typical curved river type, and the width of the estuary has had an increasing trend since the 18th century. The evolution mechanism of the Huaihe estuary is that the tidal current limit continuously moves downstream, and the estuary continuously extends to the sea. In addition, the downstream movement distance of the tidal current limit is much longer than that of the outward extension of the estuary during the same period, resulting in a significant shortening of the estuary section. To satisfy the energy demand by runoff and tidal current, the river type of the estuary section becomes meandering and the entrance is widened. The ancient Huaihe River estuary and the modern Yellow River estuary have different dynamic geomorphological characteristics and evolution mechanisms, which cannot be simply analogized.

Soil arching, which occurs in the piled embankments, plays an important role in stress redistribution between the relatively soft subsoil and the stiffer piles. The formation of the soil arching depends on the differential settlement of the embankment fill above the pile and the subsoil. The soil arching effect is barely investigated in the literature from the perspective of differential settlement of piles and soils. Based on the discrete element method (DEM), this paper develops a classic trapdoor test model to investigate the differential settlement in piled embankment during the downward movement of the trapdoor, and to explore the formation mechanism of soil arching in equal settlement pattern by changing the width of the pile cap and the height of the embankment. Due to symmetry, only one section of the laboratory test model is simulated herein. It was found that the soil arching formed under the equal settlement pattern remained unchanged after a certain degree of development, and the height of the equal settlement did not change at 0.7(s-a), where s is the pile spacing, and a is the width of the pile cap. The height of the embankment (H) and the width of the pile cap (a) have a significant influence on the formation of the equal settlement pattern when the width of the trapdoor is kept constant. Both the decrease in “H” and the increase in “a” facilitate the differential settlement of the soil between the piles and the pile-soil, enabling the slip surface to develop upward gradually, thereby hindering the formation of the equal settlement pattern.