• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.3
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• pp.263-278
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• 2022

This paper contains experimental study for the development and performance of TBM backfill material with thixotropic properties. The LW backfill material is widely applied to fill the cavity on the back side of the shield TBM excavation, but has disadvantages such as settlement caused by strength reduction, material separation by groundwater, and reduced plasticity. In this paper, laboratory tests and a model test were conducted to assess the performance of inorganic thixotropic backfill material proposed to improve these problems. The results of laboratory tests show that 1 hr-uniaxial compressive strength of ITB was 12 times higher than LW, and the rate of bleeding of 20 hr was 8.3 times lower, and the result of flow table test was more than 27 times higher. This result indicated that the inorganic thixotropic backfill material has superior properties to LW backfill in terms of strength reduction, material separation, and thixotropy. In the model experiment, a model injection device tester was manufactured and the injection performance and filling rate were verified. When material was injected in the water, it was visually checked whether material separation occurred, and it was confirmed that the filling rate was 96% or more. Comparison results with the test of LW and ITB materials was concluded that ITB can reduce the material separation by groundwater and the occurrence of tunnel cavity.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.58-72
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• 2006

In recent years, not only the occurrences but the magnitude of earthquakes in Korea are on an increasing trend and other sources of dynamic events including large-scale construction, operation of hi띤-speed railway and explosives blasting have been increasing. Besides, the probability of exposure fir rock joints to free faces gets higher as the scale of rock mass structures becomes larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, a shaking table test system was set up and a series of dynamic test was carried out to examine the dynamic frictional behavior of rock joints. In addition, a computer program was developed, which calculated the acceleration and deformation of the sliding block theoretically based on Newmark sliding block procedure. The static friction angle was back-calculated by measuring yield acceleration at the onset of slide. The dynamic friction angle was estimated by closely approximating the experimental results to the program-simulated responses. As a result of dynamic testing, the static friction angle at the onset of slide as well as the dynamic friction angle during sliding were estimated to be significantly lower than tilt angle. The difference between the tilt angle and the static friction angle was $4.5\~8.2^{\circ}$ and the difference between the tilt angle and the dynamic friction angle was $2.0\~7.5^{\circ}$. The decreasing trend was influenced by the magnitude of the base acceleration and inclination angle. A DEM program was used to simulate the shaking table test and the result well simulated the experimental behavior. Friction angles obtained by shaking table test were significantly lower than basic friction angle by direct shear test.