Interface bond degradation and damage characteristics of full-length grouted rock bolt in tunnels with high temperature

Full-length grouted bolts play a crucial role in geotechnical engineering thanks to their excellent stability.However,few studies have been concerned with the degrading performance of grouted rock bolts caused by extensive and continuous heat conduction from surrounding rocks in high-geothermal tunnels buried more than 100 m(temperature from 28C to 100C).To investigate the damage mechanism,we examined the time-varying behaviors of grouted rock bolts in both constant and variable temperature curing environments and their damage due to the coupling effects of high temperature and humidity through mechanical and micro-feature tests,including uniaxial compression test,pull-out test,computed tomography(CT)scans,X-ray diffraction(XRD)test,thermogravimetric analysis(TGA),etc.,and further analyzed the relationship between grout properties and anchorage capability.In order to facilitate a rapid assessment and control of the anchorage performance of anchors in different conditions,results of the interface bond degradation tests were correlated to environment parameters based on the damage model of interfacial bond stress proposed.Accordingly,a thermal hazard classification criterion for anchorage design in high-geothermal tunnels was suggested.Based on the reported results,although high temperature accelerated the early-stage hydration reaction of grouting materials,it affected the distribution and quantity of hydration products by inhibiting hydration degree,thus causing mechanical damage to the anchorage system.There was a significant positive correlation between the strength of the grouting material and the anchoring force.Influenced by the changes in grout properties,three failure patterns of rock bolts typically existed.Applying a hot-wet curing regime results in less reduction in anchorage force compared to the hot-dry curing conditions.The findings of this study would contribute to the design and investigations of grouted rock bolts in high-geothermal tunnels.

Bioinspired Adaptive,Elastic,and Conductive Graphene Structured Thin-Films Achieving High-Efficiency Underwater Detection and Vibration Perception

Underwater exploration has been an attractive topic for understanding the very nature of the lakes and even deep oceans.In recent years,extensive efforts have been devoted to developing functional materials and their integrated devices for underwater information capturing.However,there still remains a great challenge for water depth detection and vibration monitoring in a high-efficient,controllable,and scalable way.Inspired by the lateral line of fish that can sensitively sense the water depth and environmental stimuli,an ultrathin,elastic,and adaptive underwater sensor based on Ecoflex matrix with embedded assembled graphene sheets is fabricated.The graphene structured thin film is endowed with favourable adaptive and morphable features,which can conformally adhere to the structural surface and transform to a bulged state driven by water pressure.Owing to the introduction of the graphene-based layer,the integrated sensing system can actively detect the water depth with a wide range of 0.3-1.8 m.Furthermore,similar to the fish,the mechanical stimuli from land(e.g.knocking,stomping)and water(e.g.wind blowing,raining,fishing)can also be sensitively captured in real time.This graphene structured thin-film system is expected to demonstrate significant potentials in underwater monitoring,communication,and risk avoidance.

Sperm cryopreservation in the human sperm bank:11-year results of the Chinese mainland sperm banking network

To the Editor:Montegazza in 1866 was the first to suggest banks for frozen human semen.[1]In 1981,China's first human sperm bank was successfully established at the CITIC Xiangya Hospital.During the previous four decades,from 1981 to 2020,there were 27 human sperm banks in Chinese mainland.Human sperm banks provide cryopreservation of spermatozoa services for males needing to preserve fertility for an extended period in the Chinese mainland.