Monitoring and correction of the stress in an anchor bolt based on Pulse Pre‐Pumped Brillouin Optical Time Domain Analysis

Abstract

Bolt is an important connection in underground construction and monitoring its stress characteristics is essential to evaluate the effectiveness of bolt. The strain information collected along a rock bolt reveals the long-term movement characteristics of rock mass, which greatly helps toward disaster prevention and risk warning.Grooving on the surface of a bolt and embedding an optical fiber is one of the main methods for monitoring the anchorage performance and stress distribution around the bolt in underground engineering. In this study, Pulse Pre-Pumped Brillouin Optical Time Domain Analysis (PPP-BOTDA) technology is used to evaluate the stress, axial force, and shear stress distribution of the bolt under tensile load for different types (grooved and nongrooved) of bolts embedded in concrete with resin as anchoring agent. The results show that the PPP-BOTDA sensor can be used to monitor the stress state of the bolt embedded in concrete with resin as anchoring agent when the bolt is subjected to a tensile force. However, the apparent stress value measured in this way is not the actual stress value of the bolt, but is an increased value caused due to the groove. The closer to the exposed end of the bolt, the greater is the deviation between the apparent stress value and the actual stress value of the bolt. Based on the monitoring results from this experimental study, a stress reduction calculation method is proposed, which can change the measured value into the actual stress of the bolt. K E Y W O R D Saxial force, bolt, PPP-BOTDA technology, pullout test, shear stress 2012 |

Wrapping Nanocellulose Nets around Graphene Oxide Sheets

“…As we observed, after the filtration, the R6G and gold nanoparticles are effectively trapped within 3.5 μm GO/CNFs membranes (Figure S11). The rejection rate for both markers can reach nearly 100 %, which is comparable with the best examples of GO membranes . This high rejection rate resulted from the small interlayer spacing and heterogeneous interactions of GO nanosheets embedded into continuous CNF network.…”

“…f) Water transport properties of GO/CNFs membrane and comparison with other reported GO‐based membranes. Abbreviations: rGO/CNT, reduced graphene oxide/carbon nanotube; GO/PNIPAM, poly(N‐isopropylacrylamide) bonded graphene oxide; NC‐GO, nanostrand channeled graphene oxide; PNIPAM/CCG, poly(N‐isopropylacrylamide) bonded chemical converted graphene . Separation performance of 3.5 μm thick membranes for Rhodamine 6G (R6G) (g) and 5 nm gold nanoparticles (h).…”

“…The water transport rate measured here strongly depends upon membrane thickness, and the thinnest membranes (600 nm) show high water transport rate of above 1000 L h −1 m −2 bar −1 . Even for thicker membranes (3.5 μm), the flux value (around 200 L h −1 m −2 bar −1 ) is still higher than that of most GO materials reported to date . To demonstrate the functionality of as‐prepared GO/CNFs nanosheets materials, we have investigated their application as nanofiltration membranes.…”

Monitoring analysis of influence of extra-large complex deep foundation pit on adjacent environment: a case study of Zhengzhou City, China

“…In addition, there are often municipal pipe networks, underground pipe corridors, subway stations, and other municipal facilities around urban foundation pit projects, such as the foundation pit of the Shanghai Hongqiao comprehensive transportation hub and the foundation pit of Shanghai Tower (Zheng and Jiao 2010;Tan and Wang 2013). The construction environment and surrounding environment of foundation pit projects are extremely complex and sensitive (Wang et al 2019;Liu, Chai, et al 2020).…”

Two dimensional nanomaterial‐based separation membranes

“…2D nanomaterial, whose thickness is one atomic layer, has attracted increasing attention in many fields since the discovery of single‐layer graphene by Geim and Novoselov from graphite via mechanical exfoliation method in 2004 . Ultrathin 2D nanomaterials are of great significance to energy storage , electrocatalysis , substance separation , and other interdisciplinary fields due to their unique properties such as superior mechanical flexibility, ultrahigh specific surface area, high selectivity, etc. .…”