Abstract

Tunnels in Tianshan are high-altitude highway tunnels, which are extra-long and high-cold. The distribution characteristics of the in-situ stress field of the entire project are crucial to the design and construction of the tunnel. Therefore, this paper first analyzes the hydraulic fracturing in-situ stress test results obtained during the preliminary and detailed survey stages of the engineering area. Second, the inversion of in-situ stress field of the super-long tunnel is proposed based on "overlapping partition-integration," and a large-scale three-dimensional numerical model with overlapping partition is established. Finally, the in-situ stress field regression of the "overlapping partition-integration," for inversion and stress field characteristic analysis of the entire engineering area are carried out based on the finite difference method. The results showed that the engineering area is primarily dominated by horizontal tectonic stress in the NNE-NE direction. When the buried depth of the tunnel is less than 300 m, between 300 m and 800 m, and greater than 800 m, the three principal stresses (σH-maximum horizontal principal stress, σh-minimum horizontal principal stress, σZ-gravity stress of overlying strata) showed the characteristics of σH > σh > σZ, σH > σZ > σh, and σZ > σH > σh, respectively. The "overlapping partition-combination" for inversion method of in-situ stress field could provide a reference for inversion of in-situ stress field of extra-long tunnel engineering.

1. Introduction

In-situ stress is an important basis for excavation design and construction of underground engineering. In the engineering field, in-situ stress testing is the most direct way to determine the stress field [1-2]. However, when in-situ stress is measured, a large number of tests cannot be performed due to the limitation of site conditions and fund constraints. Only a limited number of measuring points can be arranged in a local area for testing, and the test results can only reflect the stress field near the measuring points. Due to large buried depth and long line in extra-long tunnels, full-line testing from the surface before construction may be impossible. Therefore, it is extremely difficult to predict the distribution of in-situ stress field in the whole line of extra-long tunnel by relying solely on the measured in-situ stress.

Keywords:
geologist, artificial intelligence, geological subdiscipline, mathematics of computing, reservoir geomechanics, conference, geology, borehole, machine learning, highway tunnel
Subjects:
Reservoir Characterization, Information Management and Systems, Reservoir geomechanics
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2021. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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