JZUS - Journal of Zhejiang University SCIENCE

Journal of Zhejiang University SCIENCE A 2017 Vol.18 No.3 P.179-193

A new approach to simulate the supporting arch in a tunnel based on improvement of the beam element in FLAC^3D

Author(s): Wei-teng Li, Ning Yang, Ting-chun Li, Yu-hua Zhang, Gang Wang
Affiliation(s): Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention, Shandong University of Science and Technology, Qingdao 266590, China; more
Corresponding email(s): tchli_sd@163.com
Key Words: Tunnel, Supporting arch, FLAC^3D, Beam element, Yield criterion, Modified model

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Abstract: The beam element in FLAC^3D can be used to simulate the supporting arch in a tunnel. However, this approach has the shortcoming of its constitutive model, and the bearing capacity and surrounding rock supporting effect of the arch model will be significantly exaggerated. To simulate the supporting arch in tunnel engineering well, a new approach is proposed by improving the beam element. The yield criterion of the beam element subjected to compression-bending loads is established based on the now-available bearing capacity formulas of some typical compression-bending sections. In addition, the yield criterion is embedded in the FLAC^3D main program by using the FISH language, and the modification of the beam model and the yielding failure simulation of the supporting arch are finally implemented. Compression-bending tests and roadway tunnel arch support example analysis were performed. The results are as follows: (1) the modified model showed the dependence of the bending moment and axial force on the yielding action of the beam element under compression-bending loads; (2) the implementation program is effective and sensitive; (3) the computing deviation caused by the shortcomings of the original beam element model was effectively suppressed, the mechanical behavior and surrounding rock supporting laws exhibited by the arch model were much closer to reality, and the calculation accuracy and design reliability were improved by the new simulation approach.

This manuscript gives a modified model of the Beam structure element in the commercial code of FLAC3D. The modified model can consider the yield not only on the bending behavior but also on the axial deformation. The modification procedure of the axial yielding of the Beam structure element is described clearly, and the modified Beam has a good performance when it is subjected a compression-bending load. An example analysis of roadway arch support using the modified Beam is given. According to the results, the difference between the modified Beam with unmodified Beam is obvious.

基于FLAC^3D梁单元修正的隧道/巷道拱架支护模拟方法

目的：基于常用的数值模拟软件FLAC^3D进行二次开发，弥补现有数值模拟方法的缺陷，提出一种准确有效的隧道/巷道拱架支护数值模拟方法。
创新点：1. 引入抗弯和抗压能力的相关性，改进梁单元压弯极限判据；2. 通过FISH语言编程，实现梁单元修正和拱架精确模拟。
方法：1. 通过对FLAC^3D中梁单元支撑理论的分析，明确其存在的缺陷，并利用算例进行证实（图4~6）；2. 基于传统强度理论，对梁单元现有压弯极限判据进行改进（图7和8）；3. 通过FISH语言编程，实现梁单元修正模型嵌入（图9）；4. 通过算例分析，对新模拟方法的效果进行验证（图10和13）。
结论：1. 改进了梁单元压弯极限判据，通过FISH语言编程实现了梁单元的修正及拱架屈服失效的模拟。2. 构件压弯试验和巷道拱架支护实例分析表明：修正模型体现了在压弯组合荷载作用下梁单元屈服时弯矩和轴力的相关性；实现程序是有效的且灵敏度较高；提出的新模拟方法使计算偏差得到有效压制，拱架模型呈现出的力学行为及围岩支护作用更加接近实际，计算精度和设计可靠度更高。

关键词：隧道；拱架；FLAC^3D；梁单元；屈服判据；修正模型

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