Tunnel Pressure acting on Shallow Tunnel in Unconsolidated Ground

이재호(Jae-Ho Lee),아쿠타가와 신니치(Shinish Akutagawa),김영수(Young-Su Kim),문홍득(Hong-Duk Moon) 한국암반공학회 2007 터널과지하공간 Vol.17 No.6

Terzaghi터널조합 이론은 shield 및 도심 NATM터널의 설계토압으로 현재까지도 사용되고 있다. 본 논문에서 지반의 변형거동과 한계상태를 가정한 Terzaghi 토양과의 상호 관계에 관한 조사를 위해 Terzaghi 터널토압 이론, 2차원 실내 터널 모형 설험과 변형률 연화모델을 기본으로한 비선형 수치해석을 실시하였다. 굴착에 따른 터널 토압와 지반 변형거동의 폭넓은 이해와 그들의 상호작용에 대한 효율적인 활용은 경제적인 터널 지보설계와 안정한 시공을 이끌수 있다. Terzaghi's tunnel pressure theory is generally used to estimate primary design pressures on tunnel support for shield and urban NATM tunnels until now. A trial is made in this paper to investigate the interaction between the ground deformation behavior and Terzaghi's tunnel pressure, which assumes ground's limit (or critical) state, by considering results of Terzaghi's tunnel pressure theory, two-dimensional reduced-scale model tunnel tests and nonlinear numerical analysis based on strain softening modeling. A full understanding between tunnel pressure and ground deformation behavior under the tunnel excavation and an effective utilization of this interaction lead to an economical tunnel support design and a safe construction of tunnel.

구조해석을 통한 터널내 줄눈 콘크리트 포장의 거동분석

류성우,박준영,김형배,이재훈,조윤호 한국도로학회 2016 한국도로학회논문집 Vol.18 No.2

PURPOSES: The behavior of a concrete pavement in a tunnel was investigated, based on temperature data obtained from the field and FEM analysis. METHODS: The concrete pavement in a tunnel was evaluated via two methods. First, temperature data was collected in air and inside the concrete pavement both outside and inside the tunnel. Second, FEM analysis was used to evaluate the stress condition associated with the slab thickness, joint spacing, dowel, and rock foundation, based on temperature data from the field. RESULTS : Temperature monitoring revealed that the temperature change in the tunnel was lower and more stable than that outside the tunnel. Furthermore, the temperature difference between the top and bottom of the slab was lower inside the tunnel than outside. FEM analysis showed that, in many cases, the stress in the concrete pavement in the tunnel was lower than that outside the tunnel. CONCLUSIONS : Temperature monitoring and the behavior of the concrete pavement in the tunnel revealed that, from an environmental point of view, the condition in the tunnel is advantageous to that outside the tunnel. The behavior in the tunnel was significantly less extreme, and therefore the concrete pavement in the tunnel could be designed more economically, than that outside the tunnel.

터널내 온도조건을 고려한 콘크리트 포장의 거동 및 성능 평가

류성우,박준영,김형배,이재훈,조윤호 한국도로학회 2016 한국도로학회논문집 Vol.18 No.2

PURPOSES: This paper investigates behavior and performance of concrete pavement in tunnel based on temperature data from field. METHODS : In this study, there are 4 contents to evaluate concrete pavement in tunnel, First, Comparison for distress was conducted at outside, transition, and inside part of tunnel. Secondly, temperature data was collected in air and inside concrete pavement in outside and inside tunnel. Thirdly, FEM analysis was performed to evaluate stress condition, based on temperature data from field. Finally, performance prediction was done with KPRP program. RESULTS: From the distress evaluation, failure of inside tunnel was much less than it of outside tunnel, Temperature change in tunnel was less than out side, and also it was more stable. According to result of FEM analysis, both curling stress status of inside tunnel was lower than it of outside tunnel. Based on KPRP program analysis, performance of inside tunnel was longer than outside. CONCLUSIONS : Through all study about behavior and performance of concrete pavement in tunnel, condition in tunnel has more advantages from environmental and distress point of view. Therefore, performance of inside tunnel was better than outside.

구조해석을 통한 터널내 줄눈 콘크리트 포장의 거동분석

류성우,박준영,김형배,이재훈,조윤호 한국도로학회 2016 한국도로학회논문집 Vol.18 No.2

PURPOSES: The behavior of a concrete pavement in a tunnel was investigated, based on temperature data obtained from the field and FEM analysis. METHODS: The concrete pavement in a tunnel was evaluated via two methods. First, temperature data was collected in air and inside the concrete pavement both outside and inside the tunnel. Second, FEM analysis was used to evaluate the stress condition associated with the slab thickness, joint spacing, dowel, and rock foundation, based on temperature data from the field. RESULTS : Temperature monitoring revealed that the temperature change in the tunnel was lower and more stable than that outside the tunnel. Furthermore, the temperature difference between the top and bottom of the slab was lower inside the tunnel than outside. FEM analysis showed that, in many cases, the stress in the concrete pavement in the tunnel was lower than that outside the tunnel. CONCLUSIONS : Temperature monitoring and the behavior of the concrete pavement in the tunnel revealed that, from an environmental point of view, the condition in the tunnel is advantageous to that outside the tunnel. The behavior in the tunnel was significantly less extreme, and therefore the concrete pavement in the tunnel could be designed more economically, than that outside the tunnel.

측벽부 숏크리트 보강에 의한 재래식 도로터널 단면확대

김동규(Kim, Donggyou),신영완(Shin, Youngwan) 한국지반환경공학회 2012 한국지반환경공학회논문집 Vol.13 No.12

도심지 내에서 교통량 증가로 인하여 차선확대가 요구되는 경우, 기존 터널은 증가된 차선만큼 단면을 확대할 필요가 있다. 터널 단면확대 공사로 발생되는 터널주변의 교통정체를 해소하기 위하여 터널 내에 직사각형 단면의 프로텍터를 설치하여 프로텍터 내부로 교통흐름을 유지하기도 한다. 프로텍터를 사용하면 터널 측벽 하부에서 프로텍터와 굴착 면 사이의 공간이 협소하여 록볼트 시공이 불가능할 수도 있다. 본 연구에서는 터널 측벽 하부의 협소한 공간에서 록볼트를 시공하지 않고 숏크리트 두께를 증가시켜 터널의 안정성을 확보하는 방법을 제안하였다. 기존 2차선 재래식 터널을 3차선 및 4차선 NATM터널로 확대 시공할 경우에 대하여 수치해석을 수행하였다. 터널 측벽 하부에 록볼트를 시공한 경우, 록볼트를 시공하지 않은 경우 및 록볼트를 시공하지않고 숏크리트 두께만 증가시킨 경우에 대하여 터널의 천단변위, 내공변위 및 숏크리트에 발생한 응력을 비교분석하였다. 천단변위 및 상반 내공변위는 차이가 거의 없었으며, 하반 내공변위는 터널 측벽 하부에 록볼트를 시공하지 않은 경우가 록볼트를 시공한 경우보다 최대 1.3mm 크게 발생하였다. 또한 숏크리트에 발생한 휨압축응력은 터널 측벽 하부에 록볼트를 시공하지 않은 경우가 록볼트를 시공한 경우보다 최대 1.3MPa 크게 발생하였다. 록볼트 미시공에 의해 추가 발생된 숏트리트 응력을 감소시키기 위하여 기존 숏트리크 두께의 20%(250mm →300mm, 4차선 터널)및 25%(200mm →250mm, 3차선 터널)를 추가 시공하면 록볼트를 시공할 경우와 비슷한 응력수준을 나타내는 것으로 분석되었다. The existing tunnel in urban area can be enlarged because of requirement of road-widening by traffic growth. The protector with rectangular cross section can be set up in the tunnel, which will be constructed for enlargement of width, to solve traffic jam around the tunnel. It is impossible to install the rockbolt in the lower area of tunnel due to a limited space between the protector and cutting surface. The objective of this study is to suggest the method of shotcrete thickness increase instead of rockbolt installation in the side wall of tunnel for the stability of tunnel. Numerical analysis was performed to evaluate displacement at the crown of tunnel, convergence of tunnel, and stress in shotcrete lining in 3-lane and 4-lane NATM tunnels enlarged from 2-lane conventional tunnel. There were three types of analysis condition, rockbolt installation, no rockbolt installation, and increase of shotcrete thickness without rockbolt in the side wall of tunnel. There was no difference on the displacement at the crown and the convergence of upper tunnel. In the lower tunnel, the convergence in case of no rockbolt installation was larger as maximum 1.3mm than that in case of rockbolt installation. The stress in shotcrete lining in case of no rockbolt installation was larger as maximum 1.3MPa than that in case of rockbolt installation. Numerical analysis was performed to compare the behavior of shotcrete with rockbolt with that of shotcrete, which its thickness was increased, without rockbolt. The shotcrete has an increase of 20%(250mm →300mm, 4-lane tunnel)~25%(200mm →250mm, 3-lane tunnel) in its thickness to reduce the stress in shotcrete lining. The behavior of shotcrete lining increased the shotcrete thickness by 20%~25% was similar to that of existing shotcrete lining with rockbolt.

2D numerical investigations of twin tunnel interaction

Do, Ngoc Anh,Dias, Daniel,Oreste, Pierpaolo,Djeran-Maigre, Irini Techno-Press 2014 Geomechanics & engineering Vol.6 No.3

The development of transportation in large cities requires the construction of twin tunnels located at shallow depth. As far as twin tunnels excavated in parallel are concerned, most of the cases reported in literature focused on considering the effect of the ground condition, tunnel size, depth, surface loads, the relative position between two tunnels, and construction process on the structural lining forces. However, the effect of the segment joints was not taken into account. Numerical investigation performed in this study using the $FLAC^{3D}$ finite difference element program made it possible to include considerable influences of the segment joints and tunnel distance on the structural lining forces induced in twin tunnels. The structural lining forces induced in the first tunnel through various phases are considerably affected by the second tunnel construction process. Their values induced in a segmental lining are always lower than those obtained in a continuous lining. However, the influence of joint distribution in the second tunnel on the structural forces induced in the first tunnel is insignificant. The critical influence distance between two tunnels is about two tunnel diameters.

Numerical modelling of internal blast loading on a rock tunnel

Zaid, Mohammad,Sadique, Md. Rehan Techno-Press 2020 Advances in computational design Vol.5 No.4

Tunnels have been an integral part of human civilization. Due to complexity in its design and structure, the stability of underground structures under extreme loading conditions has utmost importance. Increased terrorism and geo-political conflicts have forced the engineers and researchers to study the response of underground structures, especially tunnels under blast loading. The present study has been carried out to seek the response of tunnel structures under blast load using the finite element technique. The tunnel has been considered in quartzite rock of northern India. The Mohr-Coulomb constitutive model has been adopted for the elastoplastic behaviour of rock. The rock model surrounding the tunnel has dimensions of 30 m x 30 m x 35 m. Both unlined and lined (concrete) tunnel has been studied. Concrete Damage Plasticity model has been considered for the concrete lining. Four different parameters (i.e., tunnel diameter, liners thickness, overburden depth and mass of explosive) have been varied to observe the behaviour under different condition. To carry out blast analysis, Coupled-Eulerian-Lagrangian (CEL) modelling has been adopted for modelling of TNT (Trinitrotoluene) and enclosed air. JWL (Jones-Wilkins-Lee) model has been considered for TNT explosive modelling. The paper concludes that deformations in lined tunnels follow a logarithmic pattern while in unlined tunnels an exponential pattern has been observed. The stability of the tunnel has increased with an increase in overburden depth in both lined and unlined tunnels. Furthermore, the tunnel lining thickness also has a significant effect on the stability of the tunnel, but in smaller diameter tunnel, the increase in tunnel lining thickness has not much significance. The deformations in the rock tunnel have been decreased with an increase in the diameter of the tunnel.

Numerical studies on the radiation of train-tunnel impulse waves

Zhang, Guang,Kim, Dong Hyeon,Kim, Heuy Dong Elsevier 2018 Tunnelling and underground space technology Vol.80 No.-

<P><B>Abstract</B></P> <P>An impulse wave is always discharged from the exit of a train tunnel when a weak compression wave induced by a moving high-speed train at the tunnel entrance propagates outside of the tunnel exit. An impulse wave is a micro-pressure wave, which leads to environment problems such as noise, vibration and other structural damages in the vicinity of the tunnel exit. Currently, due to the development of the optimization and acceleration systems of the high-speed train, the train speed becomes much higher than before and environmental problems become more serious as well. Therefore, it is significantly important to find effective methods to control and reduce magnitudes of impulse waves discharged from the tunnel exit. In the present study, numerical simulations were carried out to investigate the generation and propagation of impulse waves discharged from the exit of a model tunnel. Weak compression waves with different pressure gradients were assumed at the tunnel entry for investigating the relationship between the compression wave and the impulse wave radiated from the tunnel exit. Several tunnel exit geometries with and without a flange at the exit portal of the tunnel were simulated to check their effects on the radiation of impulse waves. Coefficient of effective radiation solid angle indicating the effects of the surrounding environment near the tunnel exit was discussed in-depth. The comparison was made in terms of the magnitudes of impulse waves and coefficients of effective radiation solid angle at different boundary conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Impulse waves induced by assuming weak compression waves instead of modelling a high-speed train. </LI> <LI> Different entry compression waves. </LI> <LI> Impulse waves at the near and far fields. </LI> <LI> Effects of the length and the angle of the tunnel flange. </LI> <LI> The coefficient of effective radiation angle. </LI> </UL> </P>

Water Disaster Susceptible Areas in Loess Multi-arch Tunnel Construction under the Lateral Recharge Condition

Zhengjun Mao,Xiaokang Wang,Ning An,Xiaojun Li,Rongyu Wei 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.10

The water disaster susceptible areas in loess multi-arch tunnels were studied. Taking Lishi multi-arch tunnel as an example, the tunnel is located in Luliang City, Shanxi Province, China, with a total length of 180 m. It is the first loess multi-arch tunnel in China. The groundwater recharge in the tunnel site is dominated by rainfall, and the surrounding rock of the tunnel is unsaturated. Considering the lateral recharge of groundwater, in this study, midas geo-technical analysis system was adopted to simulate the construction process of a middle pilot tunnel–bilateral pilot tunnel of a loess multi-arch tunnel, accounting for fluid-solid coupling. The variations in the surrounding rock stress and seepage fields of loess multi-arch tunnels during the construction process were studied. A water disaster susceptible area in a loess multi-arch tunnel was confirmed based on the catastrophe area of the displacement, stress, gross head, pore water pressure, and seepage velocity. The result show that the water disaster susceptible areas for loess multi-arch tunnels during the construction period mainly concentrated in the mid-partition, arch springs of the left and right tunnels, and the tunnel face.

국내 터널 구조물의 변상에 관한 조사 및 분석

배규진,이성원,조만섭,이광호 사단법인 한국터널지하공간학회 2001 한국터널지하공간학회논문집 Vol.3 No.3

In this study, we carried out investigation and analysis on dam ages in tunnels on order to provide the basicinformation for the safety assessment of tunnels and to minimiz e the potential damage of the same kind as investigated.The frequencies of occurrence in terms of 4 items, i.e., servic e life interval, type of the damage, cause of the damage, andgeological condition, were examined and summarized based on 44 foreign and domestic cases of tunnel damages. Also,we carried out a survey research of which the content included 28 questions on the tunnel safety assessment. Theanswers collected from domestic experts in tunneling suggested that the most probable cause of the tunnel damages wascracking in tunnels at 42~58%. They also suggested that the poo r constrution work strongly caused the damages.Therefore, to ensure tunnel safety, high quality of constrution should be maintained as examined. The types of damageand their extent of influence on the overall tunnel safety are of practical importance to be used in the artficial intelligentsystem for tunnel safety assessment.