• Journal of the Korean GEO-environmental Society
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• v.24 no.8
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• pp.13-20
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• 2023

Tunnelling through the geological anomalies has widely known to have many difficulties such as bottom heave, crack of lining, squeezing and so on. To stabilize the tunnel during the construction or after construction, various reinforcing methods have been introduced and applied such as micropiling at the bottom of tunnel to prevent the bottom heave. In this study, long-term behavior of tunnel in the presence of geological anomalies was predicted using numerical analyses. To this end, material properties for swelling rock model capable of representing the rock swelling behavior was obtained using matching process with measured data to validate the adopted model. After the model validation, simulations were performed to predict the long-term behavior of tunnel in the geological anomalies.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.605-621
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• 2009

대심도 암반을 굴착함에 따라 암석강도 및 암반응력 등의 특성에 따라 Rockburst 등과 같은 취성파괴 및 Squeezing 등과 거동을 나타낼 수 있으며, 이러한 대심도 암반거동은 터널 및 지하 공동 시공중 위험요소로 작용하여 안정성에 심각한 영향을 줄 수 있다. 따라서 대심도 암반구간에 터널을 건설하는 경우에는 합리적인 설계 및 시공을 달성하기 위해서는 대심도 암반에 대한 지질 및 암반특성을 정확히 이해하는 것이 필요하며, 대심도 암반특성에 적합한 보강 및 시공대책을 수립하도록 하여야 한다. 본 고에서는 대심도 암반구간에서의 위험도 평가 및 터널 설계사례를 검토하여, 대심도 암반특성을 고려한 터널구조물 설계시 합리적인 방안을 도출하고자 하였다.

• Advances in concrete construction
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• v.11 no.5
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• pp.357-365
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• 2021

High deformable concrete (HDC) elements have compressive strength rates equal to conventional concrete and have got a high compressive strain at about 20% to 50%. These types of concrete elements as prefabricated parts have an abundance of applications in the construction industry which is the most used in the construction of tunnels in squeezing grounds, tunnel passwords from fault zones or swelling soils as soft supports. HDC elements after reaching to compressive yield stress, in nonlinear behavior have hardening combined with increasing strain and compressive strength. The main aim of this laboratory and numerical research is to construct concrete elements with the above properties so the compressive stress-strain behavior of different concrete elements with four categories of mix designs have been discussed and finally one of them has been defined as HDC element mix design. Furthermore, two columns with and without implementing of HDC elements have been made and stress-strain curves of them have been investigated experimentally. An analysis model is presented for columns using finite element method adopted by ABAQUS. The results obtained from the ABAQUS finite element method are compared with experimental data. The main comparison is made for stress-strain curve. The stress-strain curves from the finite element method agree well with experimental results. The results show that the dimension of the HDC samples is significant in the stress-strain behavior. The use of the element greatly increases energy absorption and ductility.

• Geomechanics and Engineering
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• v.34 no.6
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• pp.637-648
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• 2023

When an earth pressure balance (EPB) shield machine bores a tunnel in gravelly sand stratum, the excavated natural soil is normally transformed using foam and water to reduce cutter wear and the risk of direct muck squeezing out of the screw conveyor (i.e., muck spewing). Understanding the undrained shear behavior of conditioned soils under pressure is a potential perspective for optimizing the earth pressure balance shield tunnelling strategies. Owing to the unconventional properties of conditioned soil, a pressurized vane shear apparatus was utilized to investigate the undrained shear behavior of foam-conditioned gravelly sands under normal pressure. The results showed that the shear stress-displacement curves exhibited strain-softening behavior only when the initial void ratio (e₀) of the foam-conditioned sand was less than the maximum void ratio (e_max) of the unconditioned sand. The peak and residual strength increased with an increase in normal pressure and a decrease in foam injection ratio. A unique relation between the void ratio and the shear strength in the residual stage was observed in the e-ln(τ) space. When e₀ was greater than e_max, the fluid-like specimens had quite low strengths. Besides, the stick-slip behavior, characterized by the variation coefficient of measured shear stress in the residual stage, was more evident under lower pressure but it appeared to be independent of the foam injection. A comparison between the results of pressurized vane shear tests and those of slump tests indicated that the slump test has its limitations to characterize the chamber muck fluidity and build the optimal conditioning parameters.