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29 March 2020, Volume 39 Issue 03 Previous Issue    Next Issue
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Overview
Energy Saving
Construction and Structural Maintenance
Tunnel Engineering in High Altitude and Cold Regions
Mechanization and Prefabricated Construction
Risk Assessment and Control


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Overview

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Reliability Analysis Methods in Tunnel Construction and Operation ZHANG Wengang1,2,3，WANG Yan2，ZONG Zixu2，ZHOU Xiaowan2，LIN Wei2 2020, 39(03): 1-13.  DOI: 10.3969/j.issn.1674-0696.2020.03.01 Abstract ( )   PDF (864KB) ( )   With the development and utilization of underground space resources, the reliability analysis of tunnel engineering is becoming more and more important. Firstly, the three main uncertainties in tunnel engineering were illustrated, such as the variance of rock and soil mass, the statistical uncertainty and the uncertainty caused by inaccurate model. Secondly, the commonly-used reliability analysis methods in tunnel engineering were introduced, such as direct integral method, moment method, point evaluation technique, Monte Carlo simulation, random field simulation, response surface method. And then, the current situations of reliability analysis during tunnel construction and operation were described respectively. In the existing research, for the tunnel under construction, there were more researches on the reliability of the tunnel face and the tunnel section, while the reliability analysis of the influence of tunnel excavation on adjacent buildings was relatively less. For the operating tunnels, the current reliability analysis of tunnels mostly focused on a single disease without comprehensively considering the impact of various diseases. Finally, the main four development trends of the reliability analysis of tunnel engineering were predicted, that is the uncertain characterization of parameters, the development of efficient reliability calculation method, the risk analysis of new and existing tunnel and adjacent structures, the establishment of the comprehensive risk assessment system for operating tunnels. It is expected to provide reference and suggestions for the reliability study of tunnel engineering in the future. References | Related Articles | Metrics

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Present Situation and Prospect of Mechanization Construction of Mountain Highway Tunnels WU Mengjun1,2,3, WU Qingliang4 2020, 39(03): 14-21.  DOI: 10.3969/j.issn.1674-0696.2020.03.02 Abstract ( )   PDF (1324KB) ( )   The relevant literature on the mechanized construction technology of mountain highway tunnel in China from 2001 to 2019 was comprehensively analyzed. Firstly, the main mechanized construction equipment used in each construction process of the tunnel was summarized. At the excavation and primary support stages, the mechanized construction equipment mainly included rock drilling trolley, inverted arch trestle, wet spraying manipulator and arch erection trolley, etc. And in the secondary lining construction and maintenance, waterproof and drainage construction and other processes, the mechanized construction equipment mainly included the new intelligent lining trolley, temperature control spray maintenance trolley, waterproof slab paving trolley, as well as auxiliary supporting mechanical equipment such as ditch cable trough trolley, intelligent grouting machine, and tunnel dust removal equipment. Secondly, the main problems existed in the current mechanized construction in China were pointed out: the mechanization construction degree of highway tunnel was generally not high; the adaptability was poor; the project cost was high; the technical management personnel was lack; the current standards and specifications were not matched with the design, etc. Finally, the development direction of mechanization construction of mountain highway tunnel was prospected: informatization, intellectualization, complete set and assemblage. References | Related Articles | Metrics

Energy Saving

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Contrastive Research on Calculation Method of Luminance in the Threshold Zone of Shuangshan Tunnel LIANG Bo1,2, CHEN Hongyang1 2020, 39(03): 22-26.  DOI: 10.3969/j.issn.1674-0696.2020.03.03 Abstract ( )   PDF (2619KB) ( )   Aiming at the differences between the current domestic standard (code for Design of Road Tunnel: JTG/T D70/2—01—2014) and CIEs calculation method for the luminance in the threshold zone, the calculation method of the 20° equivalent veiling luminance was deduced, taking Chongqing Shuangshan tunnel as an example. The luminance in the threshold zone of the 20° and 56.8° field of view in different sky environments was calculated by the perceived contrast method, and compared with the normative design value. The research results show that: the perceived contrast method considers a larger field of view, and more consideration is given to the integrated influence of the surrounding scene environment, the atmosphere and the windshield of the car on the biological factors such as the drivers visual characteristics. Therefore, its calculation result is higher than the normative value. The result of the perceived contrast method using backlight illumination is about 52% smaller than that of symmetrical illumination. Backlighting can reduce the energy consumption of tunnel lighting. The sky environment has a significant influence on the luminance in the threshold zone. The luminance in the threshold zone needs to be ranked based on the sky type. References | Related Articles | Metrics

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Evaluation Method of Highway Tunnel Lighting Based on Indoor Simulation of Light Environment and Visual Performance Experiment HE Shiyong1, LIANG Bo1, ZHONG Shengming2, PAN Guobing2 2020, 39(03): 27-35.  DOI: 10.3969/j.issn.1674-0696.2020.03.04 Abstract ( )   PDF (1936KB) ( )   With the rapid increase of highway tunnel mileage in China, the problems such as high energy consumption, low quality of lighting and frequent traffic accidents in the operation become increasingly prominent. Based on the current lighting design and operation status of highway tunnels, the indoor simulation of lighting environment of highway tunnels was carried out with the perspectives of drivers “static spatial visual perception” and “dynamic luminance adaptation”. The effects of environmental parameters such as the spectral power distribution (SPD) and the correlated color temperature (CCT) on the visual state of the tested subjects were quantitatively characterized by visual performance based on reaction times. The results show that in the interior zone of highway tunnels (especially long and extra-long tunnels), the visual performance of the tested subject increases with SPD of the light environment in the visual field perception domain, that is SPD1, SPD2 and SPD3 in turn, and increases with the increase of CCT of the environment. The visual performance corresponding to the visual task is significantly lower than that corresponding to other tasks when the luminance gradient decreases. The short adaptation time under the dynamic dark adaptation helps to enhance the tested subjects visual performance in the process of decreasing the luminance gradient. The maximum spectral sensitivity of the drivers vision system gradually transits to the shortwave direction under the characteristics of dynamic dark adaptation. References | Related Articles | Metrics

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Threshold Zone Length of Road Tunnel Based on Visual Performance DU Feng1,2, LIU Hui1,WENG Ji2,HU Yingkui2, CAI Xianyun2 2020, 39(03): 36-43.  DOI: 10.3969/j.issn.1674-0696.2020.03.05 Abstract ( )   PDF (528KB) ( )   In recent years, road tunnels have developed rapidly, which greatly facilitates transportation; and the lighting zone length study has become more and more significant. The length of the entrance reinforced lighting section in the regulations and the bases proposed by different codes, including CIE, EU, UK, USA, Japan and China, was contrasted, and it was found that there was a big difference in these regulations and bases. In order to analyze and solve this problem, the visual performance method was adopted to simulate the light environment of the highway tunnel site through laboratory experiments, which was mainly for reaction time index. The reaction time of several testers under different light environment was tested, and the adaptation time of each entrance reinforced lighting step was obtained by the preliminary fitting analysis of the data. The relationship expression between the adaptation time and the luminance of each lighting step was obtained by fitting the adaptation time and the luminance change of each entrance reinforced lighting section. By using the proposed relationship expression, the corresponding adaptation time values under the luminance steps of different entrance reinforced lighting sections could be obtained, and the length of each reinforced lighting step could be further deduced. Finally, the obtained results were compared with the existing specifications. The research results show that: the obtained adaptation time of entrance section is longer, the transition section has little difference, and the relative energy saving performance is slightly worse; whereas the safety is obviously enhanced. References | Related Articles | Metrics

Construction and Structural Maintenance

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Upper Limit Solution for Anti-uplift Instability of Narrow Foundation Pit under Continuous Deformation Field WANG Mingnian1,2，ZENG Zhengqiang1,2，LIU Dagang1,2，WU Xuedu3 2020, 39(03): 44-50.  DOI: 10.3969/j.issn.1674-0696.2020.03.06 Abstract ( )   PDF (682KB) ( )   In the upper limit analysis of anti-uplift instability of foundation pit in the past, the soil was usually divided into several rigid bodies, which neglected the shear deformation inside the rigid bodies and the size effect of foundation pit; thus, it was difficult to reflect the actual deformation mechanism of the foundation pit. The displacement increment of Rayleigh distribution function was selected, and the deformation model of narrow foundation pit under Terzaghi mechanism was established. The expression of the shear strength of soil considering soil anisotropy and over-consolidation ratio was adopted. According to the principle of upper bound method, the calculation method of safety coefficients of anti-uplift considering the geometric size of foundation pit was proposed. The influence rule of important parameters, including the geometric size of foundation pit, over-consolidation ratio and anisotropic coefficient of shear strength, on the safety coefficients of anti-uplift was quantitatively analyzed. The comparison between the classic foundation pit failure cases and the results of nonlinear finite element analysis shows that: in the proposed method, the influence of internal bracing erection on the stability of foundation pit is taken into account, and the influence of the width and anisotropy of foundation pit on the safety coefficient of anti-uplift can be considered. References | Related Articles | Metrics

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Factors Affecting the Settlement of Double-Line Shield Tunnel Construction BAO Xiaohua1，ZHANG Yu1，XU Changjie2，FU Yanbin1，CUI Hongzhi1，XIE Xiongyao3 2020, 39(03): 51-60.  DOI: 10.3969/j.issn.1674-0696.2020.03.07 Abstract ( )   PDF (1701KB) ( )   Ground settlement caused by shield tunnel construction is always a difficult problem in the engineering practice. Based on the double-line tunnel between Fangzhuang and Shilihe Station on line 14 of Beijing Metro, a three-dimensional numerical calculation model was constructed to simulate the successive excavation and grouting process of the double-line tunnel. The modified Cam-Clay model was used to calculate the soil mass, and the stiffness transfer method was used to simulate the shield tunneling process and synchronous grouting construction process. The influence of grouting pressure, grouting volume behind the wall, consolidation and hardening of slurry changing with time and successively tunneling construction on the surface deformation was analyzed. The results show that reasonable determination of grouting volume and grouting pressure can effectively control surface subsidence. The calculation results of settlement considering the hardening of slurry is larger than that without considering the hardening factors. Under the condition of optimum grouting pressure and grouting volume, the calculated results are in good agreement with the measured values when the volume strain method is used and the slurry hardening is considered. In the later stage, the line construction not only causes the further settlement of the stratum, but also increases the structural deformation of the first constructed tunnel. References | Related Articles | Metrics

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Groundwater Buoyancy Based on the Theory of Statics NI Wenbing 2020, 39(03): 61-68.  DOI: 10.3969/j.issn.1674-0696.2020.03.08 Abstract ( )   PDF (750KB) ( )   Aiming at the reduction of the under groundwater buoyancy of underground structure,a theoretical basis was established.Firstly, two kinds of visualized soil accumulation models were proposed,which represented the real sand and clay respectively. Next,the similarities and differences of the two models were compared and it was pointed out that they had the characteristics of interconnection between pores. Then,in view of the statics concept and method, the accumulation model of contact flange soil abstracted from visual-particle accumulation models of soil was obtained, and the interaction between the size of groundwater buoyancy and the contact between soil particles was analyzed.The research results show that a new concept of soil mechanics can be established, that is contact-area ratio of solid particles, which represents the contact relationship between solid particles in soil layer. It is further concluded that there is always a reduction in the buoyancy of the groundwater water of the underground structure, and the reduction coefficient is directly proportional to the contact-area ratio of the solid soil particles. Besides,the buoyancy of underground structure under the condition of multi-soil foundation was analyzed. The results show that the water buoyancy of underground structures may be affected by the soil layers in a certain depth range of the basement,and the specific theoretical algorithm is given. References | Related Articles | Metrics

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Model Test of Influence of Cavities behind Lining on the Safety of Tunnel HUANG Feng1,2, LIU Xingchen1,2, JIN Chenghao1,2, LIN Zhi1,2 2020, 39(03): 69-77.  DOI: 10.3969/j.issn.1674-0696.2020.03.09 Abstract ( )   PDF (1256KB) ( )   The phenomenon of cavity behind the tunnel lining as one of the main diseases occurs in the construction and operation of road tunnel, which changes the interaction between tunnel lining and surrounding rock and induces the concentration even failure of tunnel structure. The physical model test was adopted, and three test cases were simulated: no cavity, one cavity and multiple cavities. By comparing the variation rule of surrounding rock pressure, lining axial force and bending moment under the action of overburden load, the following main conclusions are obtained: ①When there is no cavity behind the tunnel, the lining and the surrounding rock contact well, and the surrounding rock pressure, lining axial force and bending moment will increase with the increase of overburden load. ②When there are cavities behind tunnel lining, the surrounding rock pressure cant be passed to the lining structure in the range of cavities. In that way, the rock pressure, axial force and bending moment of lining will reduce with the increase of overburden load; but the lining structure is easy to crack because of the increase of eccentricity. ③The influence of the cavity behind the lining on the safety factor of the lining vault is the greatest, the more the number of cavities, the more obvious the reduction of the safety factor, but the distribution law of the safety factor in the tunnel cross-section has not been changed. References | Related Articles | Metrics

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Full-Scale Test Analysis of Flexural Behavior of Composite Arch Reinforced Lining SANG Yunlong1,2, SUN Zhou1, ZHANG Qiang1 2020, 39(03): 78-83.  DOI: 10.3969/j.issn.1674-0696.2020.03.10 Abstract ( )   PDF (1060KB) ( )   It is not clear how to determine the flexural performance of reinforced structure and load sharing between old and new structures after composite arch is used to reinforce the cracked lining of tunnel. Taking the medium damage (the crack depth reaching 1/3 lining thickness) in the vault of local lining as the research object, the full-scale test by prefabricating crack of the original lining was adopted. The bending resistance test about the crack lining strengthened by the complex set of arch was carried out and the deformation of reinforced structure, the variation rule of cross-sectional bending stiffness changing with the load and the failure mode were analyzed.Combined with the test data, the distribution principle of the reinforcement structure load and the calculation method of the bending capacity were discussed. The tests show that: when medium-damage lining is reinforced with composite arches, ①the new and old structures share the load and deformation together before the existing cracks of the original lining are penetrated; the load after the penetration is mainly carried by the new arch; ②the newly added arches are evenly distributed and not extended to the original lining, which effectively improves the waterproof performance of the tunnel; ③the short-term stiffness of the reinforced structure can take the sum of the short-term stiffness of the original lining and the new arch; when the external load changes little, the internal force and the design reinforcement parameters can be calculated according to the stiffness distribution principle; ④the reinforced structure is subjected to bending failure load, which is consistent with the damage load of the newly added arches under the individual force; when the external load changes greatly, the reinforcement parameters should be designed according to the additional force of the new arch. The test results verify the reinforcement effect of the composite arch to a certain extent, and the calculation conclusions of load distribution and bearing capacity can be used as reference for the reinforcement design. References | Related Articles | Metrics

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Shear Behavior of Tunnel Concrete Subjected to Hybrid Stress State ZHANG Zhongya1,2,3, JIN Xiaoguang1,2,3, ZHANG Zhaobing1,2,3 2020, 39(03): 84-93.  DOI: 10.3969/j.issn.1674-0696.2020.03.11 Abstract ( )   PDF (1910KB) ( )   Underground excavation adjacent to existing tunnels/stations may induce unloading of stress and/or shear diastrophism in the excavation-disturbed zone. However, the impact of such hybrid stress state on the shear failure and deformation characteristic of tunnel concrete is not clear. The direct shear test on tunnel concrete specimens under hybrid stress state was designed to investigate the impact of this kind of hybrid stress state on the shear behaviors. The implement of this kind of hybrid stress state consisted of three main steps: ① loading the normal stress to the initial normal stress (INS); ② loading the shear stress to the initial shear stress (ISS); ③ unloading the normal stress and simultaneously re-loading the shear stress until the failure occurred. Different combinations of INS and ISS were considered during the test. The results show that this hybrid stress state significantly affects the shear failure and deformation characteristic of tunnel concrete specimens. For example, with the increase of INS, the shear displacement in step-③ (Vu) decreases and the normal displacement in step-③ (Uu) increases. As ISS increases, however, Vu decreases and Uu just has a little undulation. A larger unload amount (mu) doesnt always give rise to a larger displacement in step-③. In addition, the hybrid stress state results in an elevation of failure shear stress (τf) and a reduction of unload amount (mu) under current test conditions. References | Related Articles | Metrics

Tunnel Engineering in High Altitude and Cold Regions

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Optimal Length of Forced Ventilation in Construction of Long Tunnel at High Altitude ZHAO Ningyu1,2，LYU Chenfu1，CHEN Hongyang1，HU Shilin1 2020, 39(03): 94-99.  DOI: 10.3969/j.issn.1674-0696.2020.03.12 Abstract ( )   PDF (530KB) ( )   There are many challenges in the construction of long tunnels in high altitude areas. Ventilation in the construction of long tunnels at high altitude under the conditions of low pressure and low oxygen content is an important research topic. In the existing engineering practice of construction ventilation of long tunnels at high altitude, the ventilation mode of combination of the forced type and roadway type was mostly adopted, and the length of forced ventilation section was determined only by construction experience and construction task. The theoretical research on the demarcation of length between the forced type and roadway type was rare. At present, the research on the forced ventilation distance mainly focused on the analysis of the limit ventilation distance under specific conditions, which was a lack of direct calculation of the forced ventilation length without considering the construction process. Based on the principle of flow conservation, combining with the experience of the forced ventilation in tunnel construction in low altitude areas, the optimal length correction formula of tunnel forced ventilation in high altitude area was obtained. Based on the theoretical formula used in the construction of Mila Mountain Tunnel Project, the ventilation scheme was developed, and the dust concentration and CO concentration in the tunnel at 30 minutes after excavation and blasting were monitored and recorded on site. The feasibility of the theoretical formula was verified by analysis. References | Related Articles | Metrics

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Laying Length of Tunnel Thermal Insulation Layer and Anti-freezing Measures of Lining in Cold Region XIA Caichu1,2，WANG Chao1， HUANG Wenfeng2 2020, 39(03): 100-106.  DOI: 10.3969/j.issn.1674-0696.2020.03.13 Abstract ( )   PDF (1928KB) ( )   For tunnels in cold regions, in previous studies, the section with the lowest annual temperature of 0 ℃ in non-frozen section of tunnels in cold regions was generally regarded as the end point of thermal insulation layer laying. Based on the Zhihaidai highway tunnel in Qinghai province, with the help of finite element calculation software ANSYS, the direct coupling method was adopted to optimize the laying length of thermal insulation layer in the non-frozen soil section of Zhihaidai tunnel. The results show that it is more suitable to lay the thermal insulation layer of Zhihaidai tunnel with a length of 600m, rather than to lay the insulation layer to the place 650m away from the tunnel portal with an annual minimum temperature of 0 ℃. According to the characteristics of tunnel lining affected by freeze-thaw cycles, the freeze-thaw resistance and freeze-proof measures of tunnel lining in cold regions under freeze-thaw cycles were summarized. For tunnels in cold zone, the freeze-thaw cycle of lining can be improved by improving the frost resistance of concrete, setting up cold proof and heat preservation doors and installing snow proof shed. For Zhihaidai tunnel, by increasing the frost resistance grade of concrete to F800, the safety factor of lining structure will not be reduced during the operation period of 100 years. References | Related Articles | Metrics

Mechanization and Prefabricated Construction

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Key Technology of Assembled Lining Structure in Drill-Blasting Method of Highway Tunnel LIN Zhi1, HAO Li1, LI Yuwen2, TAN Zhong1 2020, 39(03): 107-112.  DOI: 10.3969/j.issn.1674-0696.2020.03.14 Abstract ( )   PDF (820KB) ( )   At present, the drill-blasting method is often used in the construction of mountain highway tunnels in China. Most of the tunnel linings are traditional on-site pouring, which adversely affects personnel health, safety, construction efficiency and engineering quality. With the improvement of economic and transportation construction level, the tunnel construction tends to be standardized, mechanized and prefabricated. According to domestic and international engineering construction experience, the development of prefabrication and assembly technology can solve the above problems. Under the premise of the lack of relevant research and construction experience at home and abroad, the key technologies such as lining structure, type selection, block design, thickness, and joint bending stiffness were studied for the prefabricated lining structure in drill-blasting method of highway tunnel. A new type of fabricated lining structure was proposed. The beam-spring model was used to simulate the thickness and joint stiffness of the structure. The deformation and internal force distribution characteristics were analyzed to ensure the safety and reliability of the structure and to provide experience for similar projects. References | Related Articles | Metrics

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Numerical Analysis and Support Mechanism of Bolt-Steel Strip Structure in Soft Rock Tunnel REN Zhaodan 2020, 39(03): 113-122.  DOI: 10.3969/j.issn.1674-0696.2020.03.15 Abstract ( )   PDF (1618KB) ( )   In order to study the supporting effect of the bolt-steel strip structure in the soft rock highway tunnel and to promote its application development, the FLAC3D was used for numerical analysis of the V-class surrounding rock highway tunnel excavated by the two-step method. According to the connection method of the structural members of the anchor, the simulation method of bolt-steel strip structure was proposed and the model was established. The displacement and stress of surrounding rock and the mechanical characteristics of supporting structure of four kinds of different supporting methods were compared and analyzed. The mechanical characteristics and supporting mechanism of the structure of the tension anchor support were summarized. The results show that the bolt-steel strip support is the best way to improve the stress state of the surrounding rock, reduce the displacement of the tunnel, and play the effectiveness of the supporting structure. The bolt-steel strip support can significantly improve the stress state and deformation of the bow waist; the axial force of the anchor bolt of bolt-steel strip support is greater than that of the conventional support, and the axial force distribution is getting larger and larger from the tail to the head of anchor bolt. The stress of the transverse steel strip of the tension anchor support at each point is greater than that of the steel arch frame, especially at the arch waist. References | Related Articles | Metrics

Risk Assessment and Control

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Full-Scale Experiment Study on Full-Jet Longitudinal Smoke Exhaust of 20 MW Fire in Yanglushan Tunnel CAO Zhengmao, ZHANG Qi, CHEN Jianzhong 2020, 39(03): 123-128.  DOI: 10.3969/j.issn.1674-0696.2020.03.16 Abstract ( )   PDF (1492KB) ( )   In order to study the feasibility and effectiveness of full-jet longitudinal smoke exhaust of the Yanglushan tunnel on the G50s Shanghai-Chongqing south expressway, the full-scale 20 MW fire test for full-jet longitudinal smoke exhaust was carried out in the left tunnel of Yanglushan tunnel, which was a downhill tunnel that was not conducive to smoke exhaustion. Fuels used in the oil pan fire test were diesel and gasoline. The environment parameters inside and outside the tunnel such as temperature T, atmospheric pressure P at the tunnel portal, and humidity of atmosphere φ were tested. Meanwhile, the wind speed along the tunnel and the smoke exhaust time were also tested. The results show that: the natural wind velocity vn in the left tunnel of the Yanglushan tunnel is 1.0~1.6 m/s during the full-scale fire test, and the wind direction is opposite to the direction of smoke exhaust, which is a resistance for smoke exhaust. When 6 groups of jet fans are opened in the tunnel, the longitudinal wind velocity vi is 3.5 m/s along the downhill tunnel; when 12~15 groups of fans are opened in the tunnel, the longitudinal wind velocity vi is 5.5~7.0 m/s in the downhill tunnel. It takes about 30 minutes from the start of ignition to the time when all smoke in the tunnel is discharged out of the tunnel. Therefore, it is feasible to use the full-jet longitudinal exhaust in the Yanglushan tunnel. References | Related Articles | Metrics

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Analytical Calculation of Rise-Span Ratio of Arch Wall of Single-span Four-lane Highway Tunnel Based on the Secondary Stress Characteristics of Surrounding Rock YANG Zhongjie1，WU Jie2, ZHANG Junru3 2020, 39(03): 129-135.  DOI: 10.3969/j.issn.1674-0696.2020.03.17 Abstract ( )   PDF (676KB) ( )   Taking two-way Jiangshuiquan tunnel with eight-lane of Jinan connecting line on Beijing-Shanghai expressway as the study background, the distribution law of the secondary stress σθ of the surrounding rock around the flat elliptical tunnel was analyzed, and the relationship between the tunnel rise-span ratio m and the σθ was simulated under six conditions GK1~GK6, among them: the section of GK1 was the design section; GK2~GK3 were formed by the combination of two ellipses, and the intersection of ellipses was located at the common tangent point of three center circles at the foot of the wall; GK4 ~ GK6 were ellipses with different m. Taking σθ of the surrounding rock of the tunnel vault that was the most disadvantageous part of the tunnel changed from compressive stress to tensile stress as the control standard of the surrounding rock stability, the arch wall rise-span ratio m1 of the single-span four-lane highway tunnel was analyzed. The results show that the value of σθ of the flat elliptical tunnel decreases gradually from the maximum span to the middle of the span, and the flatter the tunnel is, the larger the σθ is at the maximum span and the smaller the σθ is at the middle of the span; and whether there is tensile stress or compressive stress in the middle of the span depends on the value range of the tunnel rise-span ratio m; the main factor affecting the σθ of the surrounding rock of the flat tunnel is the arch wall rise-span ratio m1; the reasonable arch wall rise-span ratio m1R of single-span four-lane highway tunnel is put forward, that is the m1R of the surrounding Ⅲ-, Ⅳ-&Ⅴ-grade rock should be less than 0.420 ~ 0.490, 0.365~0.420 and 0.280~0.365 respectively on the premise of meeting the requirements of tunnel clearance. References | Related Articles | Metrics

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Test and Analysis of Jacking Force and Friction Resistance of Large-Diameter Concrete Pipe-Jacking with Super-long Distance at Seabed CHEN Xiaoxiang1，2, CHEN Yong3, ZHAO Jianhao4, HE Lei5, CHEN Wenxing6, YE Qishen2 2020, 39(03): 136-141.  DOI: 10.3969/j.issn.1674-0696.2020.03.18 Abstract ( )   PDF (584KB) ( )   Based on the in-situ measured data of the first pipe-jacking of Xiamen Xiangan subsea comprehensive pipe gallery project, the correlation between the jacking force Fp, the average resistance friction fk and the jacking distance L were studied, so as to refine the value of the average resistance friction fk in the second pipe-jacking. The results show that: fk has a large absolute value and fluctuates frequently when L=0~20 m; fk≈3.0 kPa when L＞30 m; when L＞380 m, and fk＜2.0 kPa, fk oscillates up and down at 2.0 kPa and never exceeds 3.0 kPa. When the construction stops, fk increases significantly in the range of 2~ 5 m of recovery jacking and then it quickly falls back to normal level. The research results provide the basis for the average friction value of the second pipe-jacking and the layout of the relay wall. References | Related Articles | Metrics

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Complex Geological Modeling and Numerical and Digital Integration Based on iS3 LI Peinan1,2, SHI Lai2, LIU Jun3, LI Xiaojun2 2020, 39(03): 142-148.  DOI: 10.3969/j.issn.1674-0696.2020.03.19 Abstract ( )   PDF (5939KB) ( )   3D geological modeling and numerical simulation are important analytical tools for underground space exploitation. However, the geological modeling data are hard to apply in numerical simulation in current. One of the main reasons for the low reliability of numerical simulation results is that the distribution of strata cant be accurately characterized. Based on the multi-source data coupling modeling theory,combined with borehole data, stratigraphic contact constraints and attitude information,a geological model of complex regions was established via the Cokriging gradient interpolation method from the potential interpolation.The geological model could be imported to the iS3 platform and incorporated into the unified information management system of the project.And by the secondary development, the data of the geological model was combined with the numerical simulation,and the spatial distribution of the strata was fully considered under the requirements of the grid quality and complex construction conditions simulation.Taking Nanjing Metro line 5 as the application object,the results show that the multi-source data coupling modeling can better reveal the spatial distribution of the composite stratum in the shield crossing section.Based on the iS3 platform, the geological modeling results can be further utilized, and the uneven distribution of the stratum can be fully considered in the numerical simulation to realize the numerical digital integration. References | Related Articles | Metrics