Mechanical response characteristics and influencing factors analysis of non-parallel complex subway station-tunnel groups close proximity construction

Mechanical response and failure characteristics of tunnels subjected to reverse faulting with nonuniform displacement: Theoretical and numerical investigation

<div class="section abstract"><div class="htmlview paragraph">The origami structures have received increasing attention in recent years due to the high stiffness ratio and lightweight feature. This paper has proposed an origami-based honeycomb structure and investigated the mechanical properties of the structure. The compression response and energy absorption of the structure under quasi-static loading have been investigated experimentally and numerically. The numerical results closely matched the experimental results in terms of the compression force curve and deformation patterns. The effects of different structural parameters on the mechanical response and energy absorption characteristics were analyzed with the validated model. Finally, the comparative results show that the origami-inspired honeycomb structure, which is characterized by rotational folding mode under axial compression, has better performance in terms of mechanical response and energy absorption. Two parameters, the thickness and the height have a greater influence on the structural performance, and the angle of rotation has a lesser influence. This structure can have a better application prospect in the energy-absorbing box, B-pillar, door sill beam and other parts of the car.</div></div>

Analytical and numerical analysis on the mechanical response and damage characteristics of tunnels subjected to multiple normal faulting

Analysis of mechanical response and failure characteristics of tunnels crossing active faults considering axial force and geometrical nonlinearity

The mechanical response and anti-extrusion characteristics of filled elastomers are examined in this paper. Both room-temperature and elevated-temperature uniaxial unconstrained compression and extrusion tests were carried out on hydrogenated nitriles (HNBRs) filled with carbon black and aramid fibres. The results suggest that fibre-filled HNBRs have a better resistance to extrusion over a range of extrusion gaps and temperatures. The level of extrusion resistance and the failure modes are related to the hardness and modulus of the material. It is shown that the current practice of using the hardness measured by conventional durometers to rank and/or select elastomers for specific applications may not be appropriate for elastomers with low concentration of fibres, as materials with nominally the same hardness have different resistances to extrusion and different compression moduli.

This series of reports provides response characteristics of the head, face, neck, shoulder, thorax, lumbar spine, abdomen, pelvis, and lower extremities. In each report, the decriptions of human impact respnse are based on data judged by the subcommittee to provide the most appropriate information for the development of human surrogates. This is one of a series of reports which define human mechanical impact response characteristics for specific body regions. These reports update SAE J1460 which is intended for use by anthropomorphic test dummy designers and analytical modelers who need qualitative definitions of human mechnical impact behavior.These reports do not discuss criteria for assessing human impact injury potential, which are the subject of SAE J885. Each document in the series covers material specific to a body region and will be independently updated when new response data become available. The goal of this report is to characterize the response of human neck due to head inertial loading when the occupant is sitting in an automotive posture.

Mechanical response and gas flow characteristics of pre-drilled coal subjected to true triaxial stresses

Mechanical response and phase transformation characteristics of R-phase NiTi shape memory alloy under high strain rate compression

A novel numerical framework to simulate mechanical response and damage characteristics of mountain tunnels under faulting

The stability of coal and rock masses in water-rich mines is affected by both mine water erosion and dynamic disturbances. Thus, it is necessary to study the dynamic mechanical response and failure characteristics of coal and rock under the combination of saltwater and a high strain rate. To this end, a split Hopkinson pressure bar device was employed to investigate the effects of impact velocity, water content, and immersion liquid on the dynamic mechanical behaviours of coal and rock. The results revealed that the weakening effect of saltwater on the dynamic mechanical properties of coal and rock is much greater than that of distilled water. With increasing moisture content, the dynamic compressive strength of the coal specimens decreases monotonically, while that of the rock shows a trend of first increasing and then decreasing. The failure process and destruction of coal and rock are comprehensively affected by both the external impact load and the physical and mechanical properties of the material. The degree of damage of the coal and rock specimens increases with increasing impact velocity and water content. Moreover, the influence of various factors on the impact fracture mechanism of coal and rock under saltwater immersion conditions was revealed. These findings are highly important for the design and maintenance of underground coal and rock building structures.

Bi-directional freezing to fabricate freeze-cast ceramics with orientation gradient and uniaxial compressive deformation behavior of infiltrated composites

In order to obtain the effect of porosity on the dynamic mechanical properties and impact response characteristics of high aluminum content PTFE/Al energetic materials, PTFE/Al specimens with porosities of 1.2%, 10%, 20%, and 30% were prepared by adding additives. The dynamic compression properties and impact response characteristics of high aluminum content PTFE/Al energetic materials with porosity were studied by using a split Hopkinson pressure bar (SHPB) impact loading experimental system. Based on the one-dimensional viscoplastic hole collapse model, an impact temperature rise analysis model including melting effects was used, and corresponding calculation analysis was performed. The results show that with the increase of porosity, the yield strength and compressive strength of the material will decrease. Under dynamic loading, the reaction duration of PTFE/Al energetic materials with different porosities generally shows a tendency to become shorter as the porosity increases, while the ignition delay time is basically unchanged. In this experiment, the material response has the optimal porosity with the lowest critical strain rate, the optimal porosity for PTFE/Al energetic materials with different porosity and high aluminum content (50/50 mass ratio, size of specimens Φ8 × 5 mm) is 10%. The research results can provide an important reference for the engineering application of PTFE/Al energetic materials.

Strain rock burst is one of the main types of rock bursts. Studying the mechanical response and acoustic emission characteristics of coal under quasi-static loading is significant to control and prevent strain rock bursts. In this paper, coal’s strength, deformation, energy evolution, and failure characteristics were analyzed with different strain rates under quasi-static loading. The strength characteristics of coal show a strain rate effect to a certain extent and the elastic modulus decreases first and then increases with stain rate increasing. Moreover, the elastic strain energy of coal samples always accounts for a high proportion before failure and the failure of coal presents a combined failure mode of tensile and shear under the dominance of tensile failure. The contribution of the shear failure to coal failure increases correspondingly when strain rate increases. Under quasi-static loading, There is a range where the strain rate effect does not appear, named as strain rate effect invisible area. The high static loading stress, and direct action of high strain rate loading should be avoided to reduce the risk of rock burst, especially for isolated coal pillars. The research achievements deepen the understanding of strain rock burst and provides critical support for the prevention of strain rock burst induced by high static loading.

To investigate how joint density and drilling diameter impact the failure features of coal specimens, a numerical simulation test was conducted using PFC 2D 5.0 software. The mechanical characteristics, failure characteristics, and energy changes of borehole coal specimens with different joint densities and different drilling diameters were analyzed, and the sensitivity of the two was compared by range analysis. The results show that (1) the increase of joint density significantly reduces the bearing capacity of coal specimens, while the drilling diameter has little effect on the peak stress, but it will significantly change the failure path of coal specimens; (2) Under the condition of low joint density, the specimen is mainly characterized by tensile brittle failure, and the fragments are large. Increasing joint density shifts the specimen’s failure mode towards shear failure and produces smaller fragments; (3) With the increase of drilling diameter, the initiation and propagation of cracks are more likely to occur around the drilling, and the acoustic emission hot spots are more concentrated around the drilling. The increase of joint density leads to more complex crack distribution, and the distribution range of acoustic emission hot spots is expanded and the number is increased; (4) The joint density has a weakening effect on the elastic energy storage of coal specimens, and this weakening effect decreases with the increase of drilling diameter. and drilling affects the way of energy dissipation.

Autonomous Rail Rapid Transit (ART), featuring multi-axles, high tire pressure, and complete channelization, leads to severe rutting on conventional asphalt pavements. Semi-flexible pavement materials (SFP) were applied to ART corridors to mitigate rutting. Mechanical response characteristics were obtained by embedding sensors to understand the interaction between ART and SFP. Results found that the damage of corridor pavement shifted from rutting to top-down transverse cracking after adopting SFP. Nonresidual longitudinal tensile strains primarily caused top-down transverse cracking. The compressive stress at the bottom of corridor pavement caused by ART is 41%, 36%, and 58% higher than that of the BUS, respectively, under the condition of constant speed, acceleration, and deceleration. The maximum strain response caused by ART under a high-temperature environment was ten times higher than that of buses. These findings can provide data support for numerical simulations, material failures, and structural damage of ART corridors. Highlights Mechanical responses of semi-flexible pavement materials influenced by Autonomous Rail Rapid Transit (ART) were first captured using sensors. ART with high tire pressure exhibits a multi-axial cumulative effect in high-temperature conditions, resulting in pavement strains that can be up to ten times those of buses. After adopting semi-flexible pavement, the damage in ART corridors shifted from rutting to top-down transverse cracking. Nonresidual longitudinal tensile strains are the underlying cause of top-down transverse cracking.