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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2017 Vol.54 Issue.2 Published 2017-04-25 Article 1 Roles and Structures of Cold-Proof Drainage Tunnels for Different Permafrost Tunnels Most tunnels built in cold regions suffer from frost damages such as lining cracking, icing up on the side-wall and icy pavement, which seriously affect normal tunnel operation and threaten the safety of the tunnels.As a common water drainage method in cold areas, cold-proof drainage tunnels are widely used in tunnelling, but drainage effects are quite different for different tunnels due to minimal research of the mechanisms of cold-proof drainage tunnels and improper implementation of the cold-proofdrainage tunnels. By analyzing the roles of coldproof drainage tunnels in different permafrost situations, this paper presents the applicability of and design requirements for cold-proof drainage tunnels. Considering these drainage tunnels just function as water channels in stable frozen and local permafrost tunnels, a new section type and layout design for cold-proof drainage tunnels are proposed that reduce the construction cost of drainage systems and decrease the impact of cold-proof drainage tunnel construction on the safety and construction schedule of the main tunnel, protect the original state of the permafrost,and are favorable for the long-term stability of the tunnel structure. 2017 Vol. 54 (2): 1-8 [Abstract] ( 1412 ) [HTML 1KB] [ PDF 4771KB] ( 2119 ) 9 Earthquake Damages and Characteristics of Highway Tunnels in the 8.0-Magnitude Wenchuan Earthquake CUI Guangyao1 WU Xiugang1 WANG Mingnian2 LIN Guojin3 It is important to understand the characteristics of earthquake damage to tunnels in order to provide a reference for the aseismic design of tunnels in areas of high-intensity earthquakes. Based on the investigation and analysis of earthquake damage on highway tunnels after the Wenchuan earthquake, the characteristics of earthquake damage to various tunnel structures were studied and summarized. The characteristics of earthquake damage at the tunnel portals are as follows: the structure outside of the tunnel portal is seriously affected by a secondary geological hazard, there is little earthquake damage of the support structure at the tunnel portal in hard rock, slight damage in the form of cracking and water seepage occurs in the secondary lining at a tunnel portal in soft rock with an 8.0-intensity earthquake, and serious earthquake damage such as collapse of the secondary lining occurs in areas with an 11.0- intensity earthquake. Earthquake damage is slight for tunnels passing through inactive faults, while serious earthquake damage (collapse of the secondary lining and rock mass) occurs for tunnels passing through active faults.As for tunnel structures in ordinary sections, there is little earthquake damage in hard rock tunnels, cracking and water seepage occur in the lining of ordinary sections with alternating soft rock and hard rock in an 8.0-intensity earthquake and the soft section in a 9.0~intensity earthquake, staged lining occurs at an ordinary section with alternating soft rock and hard rock in earthquakes of 10.0~11.0 intensity, and the serious damage of collapse of the secondary lining occurs at the ordinary section with defects of the surrounding rocks. 2017 Vol. 54 (2): 9-16 [Abstract] ( 1274 ) [HTML 1KB] [ PDF 11626KB] ( 1698 ) 17 Damage to Highway Tunnels Caused by the Wenchuan Earthquake ZANG Wanjun1,2 Quantitative indicators and a classification system of seismic damages to highway tunnels were developed based on a study of the seismic damage rules for highway tunnels in the Wenchuan seismic area. The results show that: the proportion of tunnel lining crack length is the highest along the total length of tunnel, and the length of secondary lining collapse and inverted arch dislocation goes the second; the proportion of most types of damage in surrounding rock of grade V is higher than that in surrounding rocks of other grades; in the area with Ⅹ & Ⅺ seismic intensities, damage at the fault section is the worst, and the damage at the portal section comes the second; the seismic damage severity decays quickly with increased distance from the epicenter, and the tunnels most seriously damaged are mostly located less than 10 km away from the epicenter, and nearly two-thirds of them are within 20 km;the degree of seismic damage to the tunnel in hard rock decreases with an increase of buried depth, and the relation? ship between the degree of damage and buried depth is unclear regarding tunnels in soft rock; the actual seismic intensities are higher than the fortification intensities specified for the tunnels with serious damage, and as for tunnels with moderate damage, nearly two-thirds of them have higher seismic intensities than the designed ones; seismic damage is serious when the crossing angle between the tunnel axis and the seismogenic fault is 60°~90°, and it is relatively light under angles of 30°~60°; and the primary support and secondary lining can′t work cooperatively during an earthquake because of the waterproof membrane, which increases the risk of seismic damage. 2017 Vol. 54 (2): 17-25 [Abstract] ( 1172 ) [HTML 1KB] [ PDF 4187KB] ( 1404 ) 26 Analysis of the Characteristics and Mechanism of Lining Cracking for a Tunnel Group in Schist YU Li1 ZHANG Enxiang2 GUO Wei3 HE Jibin Cracking in the secondary lining of tunnels in schist was found to be common when a survey of second? ary lining integrity was conducted for the tunnels of the Gucheng-Zhuxi expressway in Hubei province. To scientifically solve the problem of cracking, the following characteristics were summarized based on an investigation of the 48 tunnels along this line: 1) it is very common to see cracking in the secondary lining of tunnels in schist; 2) cracks are mainly located at the shallow-buried entrance and exit sections; 3) numbers of cracks in the first excavated tunnel are higher than that in the tunnel excavated later; 4) the cracking pattern is mainly oblique; 5) it is easier for the secondary lining to crack at places where large deformation and collapse occur; 6) and cracking occurs 5 months after the completion of the secondary lining. Based on the above experience, laboratory tests and site investigation, the mechanism and reasons for cracking of the secondary lining were studied and it was concluded that the schist is often soft when water is encountered due to its low strength; it is difficult to complete an arch at the shallow-buried section of the entrance; asymmetrical loading is very common; the settlements at the tunnel invert are uneven; and the rock is affected by underground water and the creep effect. The following suggestions and measures are presented: the grade of surrounding rock will be adjusted; much attention should be paid to construction at the entrance and the design of middle rock pillar stability of tunnels with small spaces. 2017 Vol. 54 (2): 26-33 [Abstract] ( 1055 ) [HTML 1KB] [ PDF 4534KB] ( 2086 ) 34 Optimization of the Waterproof Structure of the Deformation Joints at the Open-Cut Section of the Gongbei Tunnel LIU Qiang In light of the investigation of current design specifications and open-cut tunnel projects, the waterproof construction method and theory of deformation joints are summarized. Based on the principle of combination of water blocking with draining for the deformation joints, a drainable waterstop may be used to enhance water tightness for tunnels near the sea as well as for submerged tunnels. Considering the geological conditions and requirements for the open-cut section of the Gongbei tunnel, a drainable waterstop may be used for the waterproofing of deformed joints, and a drain pipe junction is designed for the inner side of the tunnels and used as the drain path for leakage water. 2017 Vol. 54 (2): 34-39 [Abstract] ( 1115 ) [HTML 1KB] [ PDF 7216KB] ( 1217 ) 40 On Web-based Investigation & Management System for Subway Tunnel Structure FANG Enquan Water leakage, lining cracking and lining corrosion may occur during operation of unban subway tun? nels, which threatens the operational safety. The traditional method for disease investigation has been gradually unable to meet the requirements of metro operation management. Based on the Web Service techniques and the Java programming language, a corresponding data standard was established through an investigation & management system for subway tunnel structure and its key techniques, synchronous information acquisition and electronization were realized, the timeliness and accuracy for controlling information on tunnel structure disease were improved,and a foundation for informatization and scientization of subway tunnel maintenance work was set up. 2017 Vol. 54 (2): 40-45 [Abstract] ( 1222 ) [HTML 1KB] [ PDF 4483KB] ( 2456 ) 46 Application of BIM Techniques to the Construction of the Donggang Station of the Lanzhou Metro ZHANG Xuegang1 ZENG Shaowu1 WANG Peng2 Considering the confined construction space, tight construction schedule and strict requirements for the Donggang station of the Lanzhou metro, a thorough study iwas undertaken in terms of a 3D perspective, collision check, material limitation, iBan mobile tracking of quality, 4D construction progress and 4D document management of the construction process based on the Revit and BIM programs of the Luban series software architecture, which gives a full play of Revit series software to create precise models and good display effects as well as the strong management functions of the cloud platform. 2017 Vol. 54 (2): 46-54 [Abstract] ( 1117 ) [HTML 1KB] [ PDF 13044KB] ( 1746 ) 55 Problems with the Calculation of Forces Applied to Tunnels Based on the Terzaghi Soil Arching Theory ZHANG Haifeng MA Baosong ZHOU Wei The Terzaghi soil arching theory has been widely used in force calculations for tunnel structures, howev? er, the theoretical explanation and experimental verification are not sufficient regarding the calculation width, lateral pressure coefficient and frictional coefficient, as well as for the soil arching pattern involved in the Terzaghi formula.Moreover, the technicians are not quite clear about the physical meaning of model parameters, and the selection of parameters is not accurate enough. In this context, the physical meaning of such parameters as the calculation width,lateral pressure coefficient and frictional coefficient, as well as the soil arching pattern, are analyzed here in detail,and the effect of parameters on the calculation results for soil pressure is presented based on a comparison of different parameters. The analysis shows the calculation width and soil arch pattern have a large impact on soil pressure,and the calculation width and soil arch pattern should be chosen based on measured data, or a wider calculation width and more conservative soil arch pattern should be taken when the scope of construction disturbance is relatively large; it is safer to choose active soil pressure coefficent; the friction angle also has a large impact on soil pressure; and it is recommended that the critical friction angle or half of the critical friction angle should be used to conduct the calculation. 2017 Vol. 54 (2): 55-60 [Abstract] ( 1105 ) [HTML 1KB] [ PDF 3412KB] ( 2433 ) 61 Influence of Principal Stress Orientation on Tunnel Stability Based on the Finite-Element Strength Reduction Method ZHOU Lei ZHU Zheming LI Yuanxin Based on the finite-element strength reduction technique, the effects of principal stress orientation on tunnel stability were studied by experimental and numerical methods. In the numerical simulation, ABAQUS code was adopted to calculate the safety factor and the equivalent plastic strain on the integral point of the arched tunnel with a vertical wall under different orientations of principal stresses, and the results agree well with the experimental results. The study results show that the finite-element strength reduction method can be well applied to the analysis of tunnel stability; the orientations of principal stresses affect tunnel stability significantly; if only the factor of principal stress orientation is considered, when the angle between the major principal stress and tunnel vertical axis is 45°, the tunnel model′s compressive strength is the lowest, the safety factor is the smallest, and the corresponding tunnel stability is the worst. 2017 Vol. 54 (2): 61-67 [Abstract] ( 1130 ) [HTML 1KB] [ PDF 3409KB] ( 2253 ) 68 Long-Term Stability of Tunnels Considering the Degradation Effects of FreezeThaw Damage to Surrounding Rock WANG Zhangqiong1 YAN E′chuan The surrounding rock of tunnels in cold regions suffers from freeze-thaw damage, which has adverse ef? fects on the long-term stability of the tunnels. Based on the Tongsheng Tunnel of the Shiyan-Fangxian Expressway in the north of Hubei province, the relationship between the uniaxial compressive strength and the freeze-thaw cycle times of schist is obtained by an indoor freeze-thaw cycle test and uniaxial compression tests. Mechanical parameters of the rock mass are estimated considering the deterioration effects of freeze-thaw damage based on the HoekBrown criterion in light of the field geological survey of the rock surrounding the work face. FLAC3D was used to perform a numerical analysis on the long-term stability of tunnels under the conditions of freeze-thaw cycles, and the characteristics of the displacement field and stress field variations of the tunnel under freeze-thaw cycles times of 0, 4, 8, 12, 16 and 20 were obtained. The results show that tunnel lining deformation and principal stress both increase to different degrees under the effects of the freeze-thaw cycle. Compared with the situation, which doesn′t consider the effect of freeze-thaw deterioration damage, the deformation, maximum principal stress and minimum principal stress of the lining increase 1.3%, 5.3% and 1.5%, respectively, after 20 freeze-thaw cycles. Thus, it is necessary to consider the influence of degradation of the mechanical properties of surrounding rock on tunnel stability under the long-term effects of freeze-thaw cycles regarding support program selection and design for the support structure. 2017 Vol. 54 (2): 68-72 [Abstract] ( 994 ) [HTML 1KB] [ PDF 2633KB] ( 1659 ) 73 PFC3D-Based Analysis of the Time-Dependent Characteristics of Rock Deformation and Fracturing around a Deeply-Buried Round Tunnel LIN Zhibin1 LI Yuanhai2 GAO Wenyi2 Yang Fan The time-dependent characteristics of rock deformation and fracturing are key issues concerning the sta? bility and control of deep tunnels. Based on a deeply-buried tunnel, the discrete particle flow code software PFC3D and a physical model test were used to analyze the spatio-temporal evolution law and mechanism of rock deformation and fracturing around the deep roadway. The research results show that: 1) the deformation of the roadway surrounding rock has a "step" growth relationship with the excavation time and has an exponential decay relationship with the distance from the roadway surface; 2) moving forward, shear slip cracks occur at two sides of the roadway near the haunch and gradually expand toward the roof and floor, with the number of cracks and rupture fractal dimension increasing in an exponential decay; and 3) the shear stress transfer of the tunnel rock mass is a process of lagging and attenuation, the shear stress of the shallow-buried rock mass at two sides of the tunnel increases rapidly and results in a yield fracture, and the shear stress of the rock mass at that place transfers more deeply and leads to ductile shear failure of the nearby rock, and obvious shear slip cracks occur. 2017 Vol. 54 (2): 73-80 [Abstract] ( 1109 ) [HTML 1KB] [ PDF 15049KB] ( 1548 ) 81 Displacement Prediction of Cavern Surrounding Rock Based on the Buffer Operator Revised Metabolism Unbiased Grey Model WAN Chen1 LI Jianfeng2 Predictions for the displacement of surrounding rock is important to ensure safe high-quality construc? tion. In light of the characteristics of monotonous growth and randomness of time series regarding the deformation of surrounding rock, an exponential buffer weakening operator is introduced to eliminate the random effect on the original data series of rock mass displacement based on the theory of a GM (1,1) unbiased grey forecasting model. A buffer operator revised UBGM (1,1) metabolic unbiased grey model is put forward to predict rock mass displacement and is applied to the Pangduo key water conservancy project. The results show that the model is highly precise and reliable, thus providing a new approach for displacement prediction for surrounding rock. 2017 Vol. 54 (2): 81-86 [Abstract] ( 1028 ) [HTML 1KB] [ PDF 699KB] ( 2046 ) 87 Calculation of Ground Settlements Induced by the Construction of Twin Parallel Shield Tunnels with Small Intervals Based on the Uniform Analytical Solution WEI Gang1 WANG Xiao2 A corrected two-dimensional analytical formula is presented based on a uniform soil mass movement model for shield tunnels, and it is used to compute the total ground settlements caused by construction of twin parallel shield tunnels with small intervals. The proposed formula is applicable for the approaching construction of twin parallel tunnels under the condition of a relative horizontal distance coefficient C=L/(h+R)≤0.66, while it is inapplicable if C is larger than 0.66; the settlements curve is a“V”shape if C is lower than or equal to 0.66, it is a“V-W” shape if C is larger than 0.66 and lower than or equal to 0.79, and it is a“W”shape if C is larger than 0.79. The calculation example analysis show that: the ground settlements calculated by the proposed formula agree well with the measured values when C is lower than or equal to 0.66; the curve of ground settlements caused by approaching construction of twin parallel shield tunnels conforms with the normal distribution law but the maximum settlement sometimes may deviate from the central axis. 2017 Vol. 54 (2): 87-95 [Abstract] ( 988 ) [HTML 1KB] [ PDF 7067KB] ( 1282 ) 96 Distribution Laws of Surface Settlement Induced by Shield Construction of Twin-Tube Metro Tunnels QIU Mingming1 YANG Guolin1 WU Zhenqing2 JIANG Anlong3 LIN Yuliang1 It is inevitable for shield construction to disturb surrounding strata, and it is particularly important to control deformation induced by shield construction. Based on a metro shield tunnel project, the laws of surface settlement for a twin-tube tunnel are studied by a theoretical analysis and numerical simulation, a modified ground settlement prediction method for twin-tube tunnels is put forward, and a comparison between theoretical data and measured data is conducted. The study results show that the larger the tunnel tube interval, the more obvious the“W” -shaped curve of the settlements; the smaller the tunnel overburden, the smaller the interval L required for the transformation from a“V” -shaped curve to a“W” -shaped curve of settlements; the better the soil conditions, the smaller the scope of disturbed strata and the more obvious the features of the“W” -shaped settlement trough; it is possible to use C=L/2i to describe the surface settlement distribution features of the twin-tube tunnel, and the surface set? tlement distribution curve develops from a“V”shape to that of a“Pot”and“W”with an increase of C, and the unsymmetrical“W” -shaped distribution is related to the relative interval of the tunnel tubes; and the predicted surface settlements calculated by the proposed formula agree well with the measured settlements induced by the construction of twin-tube tunnels. 2017 Vol. 54 (2): 96-105 [Abstract] ( 1117 ) [HTML 1KB] [ PDF 9117KB] ( 1428 ) 106 Influence of Shield Tunnelling in Soft Soil on Adjacent Buildings with Shallow Foundations XUE Wen1， 2 DING Zhi2 QIN Jianshe3 WEI Xinjiang2 The construction of a shield tunnel in soft soil will affect the deformation and internal force of adjacent buildings because of the shield construction technology and the characteristics of the foundations and buildings.Based on ground loss theory, a mechanical model showing the synergistic action of the ground, foundation and structure of the shallow-foundation building above the shield tunnel axis is established. The software 1stopt is adopted to solve the differential equation for the bending of the buildings on an elastic foundation, and the distribution laws of settlement, inclination and internal force of the building above the axis varying with the position of shield driving are analyzed. The case in which the max. positive bending moment and shear force occur in the building is chosen to study such key influential factors as the soil mass loss ratio, building rigidity and coefficient of the foundation and subgrade, which causes changes to the internal force of the buildings and the law of influence. 2017 Vol. 54 (2): 106-113 [Abstract] ( 961 ) [HTML 1KB] [ PDF 3234KB] ( 2215 ) 114 Analysis of Stratum Deformation Induced by Shield Construction Adjacent to an Existing Deep Foundation Pit SUN Leijiang1 LIAO Ying2 ZHU Fengbin3 LIU Xu2 In light of the construction of a shield tunnel adjacent to an existing deep foundation pit, a scaled model test is conducted and a 3D FEM calculation model is established regarding the combined functions of the tunnel,soil mass and enclosure of the deep foundation pit. Based on a comparison of an indoor model test and numerical calculation results, the feasibility and reliability of the 3D numerical analysis is verified; the distribution characteristics and variation law of the surrounding surface settlements induced by shield tunnel construction adjacent to an existing deep foundation pit are obtained; shield tunnel construction induced displacement characteristics of the stratum of cross sections at different depths, the surface settlement distribution affected by the adjacent existing foundation pit, and the law of settlement varying with shield tunnel driving are analyzed; the displacement of the foundation pit enclosure affected by the shield tunnel is determined; and real-time monitoring is suggested for the surface settlement, stratum deformation and displacement and deformation of the foundation pit enclosure during shield tunnel construction. 2017 Vol. 54 (2): 114-120 [Abstract] ( 1038 ) [HTML 1KB] [ PDF 2700KB] ( 2029 ) 121 Mean and Non-Mean Models for the Safety Evaluation of Surrounding Rock Based on Shield Driving under a Flyover Structure SHANG Yonghui1,2 SHANG Li2 FANG Qiancheng2 ZHANG Bo3 ZHAO Ying2 Evaluation of the stability of a tunnel′s surrounding rock is one of the most important issues in the con? struction and maintenance of underground works. Based on this, a mean and non-mean numerical model are established from the perspective of material behavior, and the safety and stability of surrounding rock are evaluated aiming at the lot one shield tunnel of Shenyang Metro Line 2 under a flyover structure. The mean model focuses on analyzing the deformation of the surrounding rock, stress variation and distribution features of the plastic zone, and verifies the rationality of the calculation with the measured data. The non-mean model focuses on the micro-failure process of the surrounding rock, and the plastic-elastic damage constitutive model with the residual strength and degradation method characterized by failure element material are adopted to simulate the progressive failure process and the sound-emission law under the reduced strength of the tunnel surrounding rock. The overall structure safety fac? tor is calculated. Using the acoustic emission (AE) law, the failure mode of surrounding rock in similar cases is discussed. 2017 Vol. 54 (2): 121-128 [Abstract] ( 1052 ) [HTML 1KB] [ PDF 5937KB] ( 2004 ) 129 Secondary Lining Cracking Mechanism and the Best Time for Supporting the Zhegushan Tunnel MENG Lubo1 PAN Huangsong1,2 LI Tianbin1 ZHANG Wenju3 Causes of secondary lining cracking in tunnels are complex and it is important to identify them so that reasonable treatment measures can be proposed to ensure safety during tunnel construction and operation. Using a tunnel that passes through carbon-based phylite as an example, and in light of the cracking characteristics of the secondary lining at the exit section, the measured data at the site and the geological conditions, it is determined that the main reasons for cracking in the secondary lining are poor quality of the surrounding rock, low levels of surrounding rock and early implementation of the secondary lining. Early installation of the secondary lining will result in large tensile stress at the inner side of the secondary lining near the sidewall and haunch, and the earlier the installa? tion of the secondary lining, the larger the tensile stress, which will result in cracking of the secondary lining. It is appropriate to install the secondary lining when the deformation of the primary support is 65%~70% of the final convergence. It is recommended to put more effort into monitoring and measuring and to strictly control the installation schedule of the secondary lining. 2017 Vol. 54 (2): 129-136 [Abstract] ( 1076 ) [HTML 1KB] [ PDF 2250KB] ( 2150 ) 137 Influence of Insufficient Lining Thickness on the Safety of a Tunnel Structure ZHANG Chengping ZHANG Xu FENG Gang ZHANG Dingli Insufficient thickness of the tunnel lining will significantly change its mechanical state and threaten the safety of the tunnel structure. A numerical simulation is conducted to analyze the safety state of tunnel linings under the conditions of integral or local insufficient lining thickness based on a two-lane highway tunnel in surrounding rock of class IV. The results show that insufficient lining thickness leads to a decrease of the axial force and bending moment on the defective section of the tunnel and an obvious reduction of the ultimate bearing capacity of the tunnel structure, which significantly reduces the safety factor of the tunnel structure at the defective section. Additionally,the internal force, bearing capacity and safety factors of the defective section are strongly influenced by a local insuf? ficient lining thickness, while sections far away from the defect are relatively less affected by this. The relationship is linear between the lining thickness and the safety factor of the tunnel structure under the condition of an integral or local insufficient lining thickness, and the critical thickness of the tunnel lining for meeting structural safety requirements is determined by a regression analysis. 2017 Vol. 54 (2): 137-143 [Abstract] ( 1076 ) [HTML 1KB] [ PDF 4367KB] ( 2389 ) 144 Calculation of Evacuation Time by the Monte Carlo Method WANG Chixin Most of the previous calculations for tunnel evacuation times are based on fixed parameters, and there are large differences between assumed and actual situations, so the calculation results are less than satisfactory. Because of the complexity of the tunnel environment and the behavior of people, evacuation behavior is full of randomness. Many statistical results of random calculations are obtained through a detailed analysis of the tunnel evacuation process and by using the random data input method and the Monte Carlo method to calculate evacuation time.Statistics show the randomness of evacuation behavior and the computation results are closer to the real-life situation compared with those of a general simulation. The results show that the Monte Carlo method is simple, goal-oriented, fast, and characterized by easy parameter adjustment and application, which adapts to tunnel evacuations in complex scenarios. 2017 Vol. 54 (2): 144-148 [Abstract] ( 1075 ) [HTML 1KB] [ PDF 582KB] ( 1620 ) 149 Layout of Jet Fans Used in Double-Lane Highway Tunnels FAN Jianguo FANG Yong LEI Shuai HUANG Lei Pressure boosting is not only related to the performance of jet fans, but also to their designed locations in longitudinal and transverse sections. Due to the limited space of the double-lane highway tunnel transverse section,it is important to have a reasonable layout of fans to improve their efficiency. Universal CFD software was used to simulate the flow field of jet fans in double-lane highway tunnels. Results show that: the clear distance of two jet fans should be 1D～2D, and the best clear distance is 1.5D to reduce the mutual interference of two jet flows and the impact of the tunnel wall on the jet flow; the height of the fan should be close to the building clearance as far as possible, and the distance between the jet fan and the tunnel vault should be 1.2D to decrease the interference of the tunnel′s inner wall on the jet flow; and the longitudinal distance L should be between 100 m and 120 m, with the best longitudinal distance at 110 m in order to avoid mutual interference of two group of fans and achieve the best effect on pressure boosting. 2017 Vol. 54 (2): 149-155 [Abstract] ( 1041 ) [HTML 1KB] [ PDF 2755KB] ( 2166 ) 156 Model Test of Influence of the Shield Cutterhead Aperture Ratio on Driving Parameters JIN Dalong YUAN Dajun LI Xinggao A model test was performed to study the effects of the cutterhead aperture ratio on the main shield driv? ing parameters during shield tunnel construction. Rules of pressure variations induced by different aperture ratios of the shield cutterhead inside and outside of the earth chamber were analyzed based on the monitoring of pressure changes and the transfer and distribution of soil pressures at the panel of the earth chamber under different aperture ratios of the cutterhead. Pressure differences at the work face and earth chamber panel were discussed, correlation formulas were established based on viscous fluid mechanics and a brief analysis of the influential factors of the pressure difference inside and outside of the earth chamber is conducted; the influence of the cutterhead aperture ratio on the squeezing effect and torque of the cutterhead was discussed and two kinds of squeezing effect mechanisms were presented. The test results show that the squeezing effect induced only by the cutterhead thrust occupies about 70% of the total squeezing effect, and the squeezing effect induced by cutterhead rotation occupies about 30% of the total squeezing effect. The relationship of the aperture ratio, torque of the cutterhead and the squeezing effect was systematically analyzed. 2017 Vol. 54 (2): 156-162 [Abstract] ( 1028 ) [HTML 1KB] [ PDF 3253KB] ( 2089 ) 163 Small-Scale Model Experiments for Fires in Tunnels with Roof Openings Based on Orthogonal Design WANG Yanfu1 Zhang Biao YAN Peina To study the performance of smoke control in tunnels with roof openings under the conditions of natural ventilation and various combinations of shaft parameters, a series of orthogonal experiments were conducted. Taking the shaft width, height, group space and the number of the shaft as the controllable factors and the maximum smoke temperature under the tunnel ceiling, smoke diffusion rate and smoke sedimentation rate as the evaluation index,some optimized schemes, which aim at lowering the maximum smoke temperature under the tunnel ceiling and reducing the smoking diffusion rate and smoke sedimentation rate, were obtained. The results show that the temperature around the tunnel ceiling is lower than 100℃ in each case; the shaft width has the largest influence on the maximum smoke temperature around the ceiling; the shaft height has a large influence on both the smoke diffusion rate and the smoke sedimentation rate; and the shaft group space affects the smoke diffusion rate significantly 2017 Vol. 54 (2): 163-169 [Abstract] ( 965 ) [HTML 1KB] [ PDF 2157KB] ( 2055 ) 170 Experimental Study on Slurry Separation by Disc Centrifuge ZHOU Cuihong1 YANG Changshun1,2 ZENG Meng1,2 CHEN Peng With the development of urban rail transit in recent years, slurry shield technology has been widely used. To improve the efficiency of slurry separation, the water cycle utilization rate is increased and wastewater is reduced. A slurry separation test is conducted by a disc centrifuge, which has many discs to reduce the sedimentation height and increase the sedimentation area. At first, a separation test of a mixed liquid of water, clay and fine sand is carried out to analyze the turbidity and removal rate of the mixed liquid before and after separation, then a separation of the mixed liquid composed of the shield slurry, clay and fine sand is performed to analyze the turbidity and granularity of the mixture before and after the separation, and the stability of the mixed liquid is tested before and after adding the shield slurry. The results show that the disc centrifuge is very effective for the slurry separation and works well in respect to particles with a grain size of 40 μm to 60 μm; the average removal rate is above 90% and the separation effect is proportional to time; and after separation by disc centrifuge, the material stability is en? hanced and the turbidity is decreased, and the median size D50 is decreased significantly. The research results pro? vide a theoretical and practical foundation for higher efficiency of slurry separation. 2017 Vol. 54 (2): 170-176 [Abstract] ( 1025 ) [HTML 1KB] [ PDF 1258KB] ( 1947 ) 177 In-situ Monitoring Analyses of the Influences of Deep Foundation Pit Excavation on Adjacent Metro Tunnels and Surrounding Strata ZHANG Zhiguo1,2 Bai Qiaomu1 JIANG Yunjuan1 WANG Weidong3 The operating tunnel deformation and soil mass settlement induced by deep foundation pit excavation are highly concerning in urban rail transit construction safety management and risk assessment. Based on the Shanghai Symphony Orchestra foundation pit project and the monitoring data for the operating tunnel and enclosure structures, the rules and characteristics of surrounding ground settlements, diaphragm wall deformations, horizontal convergence and vertical displacements of the foundation pit at different construction stages are analyzed. The measured results show that the overall trend of ground settlements is one of sinking and is generally presented in a parabolic distribution; the lateral deformations of the soil mass and diaphragm walls present substantially the same variation, which moves towards the inside of the foundation pit, and the influence of excavation depth on the horizontal displacements is not a simple linear relationship; horizontal additional convergence is presented by stretching outward, and the convergence increases with the excavation of the foundation pit; and the SMW reinforcement for both sides of the diaphragm wall can effectively control the deformation of the tunnel, the surface outside of the foundation pit and the diaphragm walls. 2017 Vol. 54 (2): 177-184 [Abstract] ( 1186 ) [HTML 1KB] [ PDF 3097KB] ( 1611 ) 185 Grouting Lifting Effect on Building Settlements Induced by Seepage during Shield Tunnelling ZHENG Gang1,2 ZHANG Xiaoshuang1,2 Settlement occurred at an existing building during shield construction of Tianjin Metro Line 3 due to ground water leakage. Based on the measured data, a numerical simulation was adopted to analyze the grouting lifting effect on the existing building under the condition of water leakage, and the effects of location of the grouting points and grouting time on the grouting lifting and tunnel were also analyzed. The research results show that the compensation grouting rate is relatively high and the required grouting volume for the shallow-hole grouting is obviously much less than that of deep-hole grouting, but the fluctuation of the compensation rate is large and the building inclination increases significantly; the bending moment of the tunnel increases sharply because of the grouting pressure during deep-hole grouting, it is 2.7 times greater than that for shallow grouting, and the influential scope of tunnel bending is around 1.5 times the grouting width; and with proper timing of the grouting, the building inclination increment is relatively small while the lifting of the measuring points and the compensation grouting rate increase significantly, and the effect of grouting lifting is better. 2017 Vol. 54 (2): 185-193 [Abstract] ( 987 ) [HTML 1KB] [ PDF 4334KB] ( 1937 ) 194 The Effects of Treatment of Collapses in Shallow-Buried Loess Tunnels with Unsymmetrical Loading LAI Jinxing1 QIU Junling1 NIU Fanyuan1,2 FAN Haobo1,4 WANG Ke1,3 In order to study the effects of the treatment of collapses in loess tunnels, the main reasons for tunnel collapse are analyzed and such treatment measures as the combination of a large pipe-roof and small pipe grouting, surface treatment and treatment inside a tunnel are put forward based on the collapse event that occurred at the portal of the Ganquan tunnel on the Baotian expressway. Treatment effects are analyzed by numerical simulation and field experiments. The analysis results show that if the tunnel is buried shallowly and unsymmetrical in terms of topography, the original design concept is unsafe and the surrounding rock is soaked with water from rainfall coming in from surface cracks, it would ultimately result in tunnel collapse and surface subsidence; the deformation and force applied on the initial support and secondary lining tend to be stable and no abnormal changes occur 20 days after treat? ment; and the calculation results of the crown settlements and peripheral convergence basically agree with the measured results and the changed values are within the scope of the specification, with the tunnel structure being stable after treatment. 2017 Vol. 54 (2): 194-201 [Abstract] ( 1115 ) [HTML 1KB] [ PDF 3680KB] ( 1720 ) 202 Raise Construction Techniques for Inclined Ventilation Shaft of the Long, Deep- Buried Erlangshan Tunnel SONG Zhirong Based on the case of the extra-long Erlangshan highway tunnel, a raise construction scheme is proposed for an inclined shaft when it is not useful for the construction of a main tunnel. And key techniques for construction of cross passage above the main tunnel, cutting of the top of underground fan room, construction of various intersections and breakthrough of the incline shaft are described in detail. 2017 Vol. 54 (2): 202-206 [Abstract] ( 1145 ) [HTML 1KB] [ PDF 2404KB] ( 2114 ) 207 Application of Micro-Vibration Blasting Techniques for Hard Rock Tunnel Construction in Complex Environments CHEN Wenyin The Qingren running tunnel of Qingdao metro line 3 is located in a slightly weathered granite formation and passes underneath some preserved national historic buildings and an civil defense cavern group, with a very complex surrounding environment. To guarantee the safety of the ancient buildings and prevent the cavern group from collapsing, the safety criterion for blasting is verified by field tests; the tunnel may safely pass beneath the historic buildings and cavern group by using such measures as a large-diameter hollow cut hole, delayed ignition with a parallel cut, a millisecond delayed detonating network with different zones and pre-bored vibration attenuation holes. 2017 Vol. 54 (2): 207-212 [Abstract] ( 1051 ) [HTML 1KB] [ PDF 1533KB] ( 2259 ) 213 Key Construction Techniques for Waterproofing and Drainage of Large-Span Four-Track Railway Station Tunnels in a Soft Rock Mountain Area WANG Lianping For the long-term operation of large-span tunnels to be safe, challenging basic requirements are that the lining surface needs to be impermeable and watertight, the water drainage system needs to work well, and the surface of the filled concrete needs to stay dry without any hydrops, especially in the case of shallow overburden and unfavorable geological conditions. Based on the four-track station tunnel at the exit section of the new Wumengshan No. 2 tunnel from Liupanshui to Zhanyi of the Guizhou-Kunming railway, the key techniques for waterproofing and drainage of large-span tunnels with small and large overburdens are studied systematically, improvement measures for the waterproofing and drainage of shallow-buried tunnels are put forward, and the key points for construction quality management of waterproof sheets and drain pipelines are summarized. 2017 Vol. 54 (2): 213-217 [Abstract] ( 971 ) [HTML 1KB] [ PDF 1219KB] ( 2165 )

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