Study on Mechanical Properties of Basalt Fiber Shotcrete in High Geothermal Environment.

Yueping Tong,Zhaoguang Li,Yan Wang,Ditao Niu,Yahao Chen,Shaohui Zhang

doi:10.3390/ma14247816

Yueping Tong, Zhaoguang Li + Show 4 more

Open Access

https://doi.org/10.3390/ma14247816

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Journal: Materials	Publication Date: Dec 17, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Xi'an University of Architecture and Technology

Abstract

With the development of infrastructure, there are growing numbers of high geothermal environments, which, therefore, form a serious threat to tunnel structures. However, research on the changes in mechanical properties of shotcrete under high temperatures and humid environments are insufficient. In this paper, the combination of various temperatures (20 °C/40 °C/60 °C) and 55% relative humidity is used to simulate the effect of environment on the strength and stress–strain curve of basalt fiber reinforced shotcrete. Moreover, a constitutive model of shotcrete considering the effect of fiber content and temperature is established. The results show that the early mechanical properties of BFRS are improved with the increase in curing temperature, while the compressive strength at a later age decreases slightly. The 1-day and 7-day compressive strength of shotcrete at 40 °C and 60 °C increased by 10.5%, 41.1% and 24.1%, 66.8%, respectively. The addition of basalt fiber can reduce the loss of later strength, especially for flexural strength, with a increase rate of 11.9% to 39.5%. In addition, the brittleness of shotcrete increases during high temperature curing, so more transverse cracks are observed in the failure mode, and the peak stress and peak strain decrease. The addition of basalt fiber can improve the ductility and plasticity of shotcrete and increase the peak strain of shotcrete. The constitutive model is in good agreement with the experimental results.

Highlights

A growing number of railway and highway tunnels are being constructed imminently in the Sichuan–Tibet region of China with the advancement of the “The belt and TheRoad” strategy
One of the main functions of high temperature is considered to be accelerated cement hydration, resulting in the rapid but highly non-uniform formation of a structure. This is beneficial to the development of early strength, the increase in defects in concrete causes a decrease in homogeneity, and the coarsening of the pore structure degrades mechanical properties [2,3]
◦ C, the 7 d to 60 d flexural strength of shotcrete without fibers increased by 8.6%

Summary

Introduction

A growing number of railway and highway tunnels are being constructed imminently in the Sichuan–Tibet region of China with the advancement of the “The belt and TheRoad” strategy. The engineering of high geothermal phenomena occurs more frequently due to geological structure, magmatic activity, groundwater activity, and other factors This special environment leads to adverse effects on building procedure, while the tunnel construction deteriorates in long-term service [1]. One of the main functions of high temperature is considered to be accelerated cement hydration, resulting in the rapid but highly non-uniform formation of a structure. This is beneficial to the development of early strength, the increase in defects in concrete causes a decrease in homogeneity, and the coarsening of the pore structure degrades mechanical properties [2,3]. Liu et al [6]

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Conclusion