In recent years, firefighter accidents and people injured by the collapse of steel structures during a fire have occurred frequently, which has attracted attention National Emergency Management Department Fire Rescue Bureau. It is urgent to carry out research on early warning systems for building fire. Existing methods mainly use characteristic parameters such as temperature, vibration, structural deformation. Due complexity an actual fire, it difficult accurately predict critical...

The impacts of temperature on the surface thermal damage rock salt, gypsum and mudstone from Yingcheng salt mine, China were investigated by crack growth propagation tests at different temperatures. We found that: (a) high could strengthen molecular motion weaken cohesion among grains, so that grain boundaries more prone to slip thus develop into cracks; (b) make water molecules evaporate specimens, which should change physical properties mudstone; (c) had a significant effect interface...

The mechanical characteristics of rock salt have an important influence on the safety cavity. acoustic emission (AE) technique was used to analyze generation microcracks in under uniaxial compression condition. By monitoring whole process stress - strain curve test, damage characteristic is obtained. AE rate-strain able reflect development with better consistency evident cracks generating. failure form mainly shear condition low loading rate. After failure, a lot small crushed particles...

The rock is a kind of geological medium with damages different degrees including fissures, faults, joints, and other structural defects. Many underground engineering projects, such as mining tunnel excavation, can break the three‐dimensional stress balance state mass make it subject to two‐dimensional or even one‐dimensional stress, thus inducing concentration which leads rapid failure. In order investigate failure law defects under based on similarity theory, we first prepared rocklike...

Aiming at the problem of pulverized migration and plugging propped fractures during coal seam fracturing, we experimentally studied pressure changes blocking characteristics with deionized water solutions three surfactants including 1227 (C21H38ClN), SDS (C12H25SO4Na) TX-100 (C34H62O11). A device capable visualizing was established, simulation experiments were conducted different injection flow rates. The obtained images binarized analyzed to quantify blockage degrees facture under...

The damage degree of a reinforced concrete structure is closely related to the generation and expansion cracks. However, traditional assessment methods structures have defects, including low efficiency crack detection, accuracy extraction, dependence on experience inspectors evaluate structures. Because above problems, this paper proposes method for members combining U-Net convolutional neural network fractal features. Firstly, collected test images are input into segmenting extracting...

A negative Poisson’s ratio structure has special deformation behavior and energy absorption characteristics, is a new with broad application prospects. However, most of the current research still at micro theoretical level, there less on macro mechanical properties. Therefore, this paper proposes polyurethane elliptical (PES), uses methods experimental simulation numerical to carry out comparison concave (PCS) analyze influence length–width structure, highlighting advantages PES in...

The passivation behavior of Al88Fe6La6 glassy ribbons in NaOH and H2SO4 solutions has been studied this paper. anodic polarization shows a good up to the measurement limit, which can be ascribed heterogeneity micro- nano- scales, providing bridges transport Fe atoms into oxide film. After polarization, cracks appeared surface ribbon divided A B types. mechanism crack formation is discussed study possibly used powder manufacturing technology.

Abstract The gage cutter is the key component in a tunnel boring machine (TBM); this part affects machine’s cutting efficiency and maintains diameter. In study, series of rock tests with different parameters (cutting spacing, penetration depth, installation angle) conducted using mechanical fragmentation experimental platform Beijing University Technology to study influences these on rock-breaking performance TBM cutter. During tests, triaxial forces chips are collected analyzed. test...

Based on laboratory experiments, the paper researches effect of polyvinyl alcohol (PVA) content performance fly ash-based cement grouting materials. The test results show that addition PVA has limited initial and final setting time brings a certain but minor delay appearance hydration peak period. It enhances during slow down impermeability to material is obviously improved, it increases with growing amount content. improves flexural strength compressive sample block varying degrees,...