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An extended 3D limit analysis of slope stability considering prestressed anchor cables reinforcement

Hong Yong, Shao Zhushan, Wu Kui, Shi Guangbin, Wu Saisai, Jiang Song

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e59, 2023

EN

Prestressed anchor cables have been extensively utilized in slope reinforcement engineering. Combining limit analysis with the strength reduction method (SRM), this article presents a new method to assess the three-dimensional (3D) stability of slopes with prestressed anchor cables. Compared with traditional methods, the factor of safety (FS) calculation method is modified by considering prestressed anchor cable reinforcement by applying a horn-like shape 3D rotational failure mechanism. To validate the proposed method, comparisons between unreinforced slopes and those reinforced with a row of anchor cables are carried out using optimization algorithms and procedures. The minimum width-to-height (B/H) ratio for which the slope can be analyzed using two-dimensional (2D) analysis under different FS calculation accuracies is obtained. To evaluate the consequences of the model parameters, parametric analysis is performed, assessing the FS sensitivity, 3D effects, anchor cable axial force, anchor position, anchor orientation, slope angle, internal friction angle, and cohesion on slope stability. Additionally, slope stabilities under the reinforcement of a row and multiple rows of anchor cables are compared and analyzed. The proposed approach can guide the design and evaluation of slope reinforcement with prestressed anchor cables.

2

Crack damage evolution in concrete coarse aggregates under microwave‑induced thermal stress

Yuan Yuan, Shao Zhushan, Qiao Rujia, Guo Xuan, Wang Weitao

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e108

EN

Coarse aggregates of waste concrete can be efficiently separated from mortar under microwave irradiation. However, the microwave-induced damage in aggregates are restricting mechanical properties of the aggregates for replacing natural aggregates. Since damage evolution in rocks treated by microwave are influenced by mineralogy and microwave operating parameters, such as power and irradiation time, understanding the microwave weakening mechanism of rocks is necessary to assess and control the damage of aggregates for recovery of high-quality concrete coarse aggregates. This article develops an approach for evaluating crack damage evolution in aggregates exposed to microwave by combining theoretical analysis with experimental investigation. A theoretical heat source-matrix model based on electromagnetic and thermal properties of mineral components is established for microwave heated aggregates. Substituting microwave irradiating parameters and mineralogy of the aggregates into the model, corresponding temperature fields and thermal stress fields are solved. Cracks in aggregates after microwave exposure are observed using scanning electron microscopy (SEM) and quantified in terms of crack length, density and intensity. Crack damage varied with microwave energy is assessed by crack length and density. Crack propagation is further discussed by contrast of stress intensity factor (SIF) at the crack tip and fracture toughness of the aggregate. Cracking behavior analyzed by SIF of cracks is consistent with that obtained from quantitative analysis on SEM images. The results suggest that granite shows a stronger resistance to thermal stress damage compared with basalt under microwave exposure, and a multistage microwave treatment should be adopted for recovery of various aggregates.

3

An analysis model for the temperature and residual stress of tunnel liner exposed to fire

Qiao Rujia, Shao Zhushan, Yuan Yuan, Zhou Hang, Guo Yinbo

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

388--398

EN

The temperature and stress analysis of tunnel liner is the basis of the damage assessment of the tunnel, and it is also have a great significance to tunnel fire protection design. In this study, a thermo-mechanical coupling model is derived to study the temperature and stresses of tunnel liner under the RABT fire curve. In contrast to consideration the effects of flame impingement on the heated surface only, the heat transfer coefficient (HTC) of the heated surface of tunnel liner is considered in the proposed model. The applicability of theoretical method is verified by comparing with the fire tests. According to maximum temperature experienced and material degradation, the residual stress of tunnel liner after fire is discussed, which could provide the basic for the damage assessment after fire. Contributions of the HTC of tunnel liner on the temperature and stresses were quantitatively described. This theoretical model explains the temperature and residual stress evolution of tunnel liner under fire when considering the effect of HTC, which provides a theoretical basis for the tunnel fire proofing.

4

An analytical design method for ductile support structures in squeezing tunnels

Wu Kui, Shao Zhushan, Qin Su

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

396--408

EN

Ductile linings have been proved to be highly effective for tunnelling in heavy squeezing grounds. But there still has not been a well-established design method for them. In this paper, an investigation on an analytical design method for ductile tunnel linings is performed. Firstly, a solution in closed form for ground response of a circular tunnel within Burgers viscoelastic rocks is derived, accounting for the displacement release effect. Then based on the principle of equivalent deformation, the mechanical model of segmental shotcrete linings with yielding elements is established using the homogenization approach. Analytical prediction for behaviour of ductile tunnel linings is provided. Furthermore, the proposed design method for ductile tunnel linings is applied in Saint Martin La Porte access tunnel and the analytical prediction is in good agreement with field monitoring data. Finally, a parametric investigation on the influence of yielding elements on performance of ductile tunnel linings is conducted. Results show that the length of yielding elements poses a great influence on linings. It is feasible and effective to increase the length of yielding elements to obtain the pressure within the bearing capacity of linings. However, yield stress of yielding elements does not significantly affect the performance of the lining. It is suggested to apply yielding elements with relatively higher yield stress in linings for higher stability.