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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2015 Vol.52 Issue.3 Published 2015-06-25 Article 1 Study of Influential Factors and Measures for Low Carbonization During the Construction of Shield Tunnels Li Qiaosong1 Bai Yun2 Li Lin2 In tunnel engineering at present, carbon emissions are generally estimated during the planning design stage or obtained by statistics of total emissions after completion. However, the difference of carbon emissions in each ring and relevant influential factors are seldom considered. For this paper, based on the emission coefficient method, real-time statistics were determined regarding the in-situ energy consumption of the South Hongmei Road tunnel, and the actual carbon emissions per ring were obtained. Furthermore, the difference of the actual carbon emissions in each ring is analyzed and discussed by considering the parameters of stratum and construction. The results show that: 1) the average carbon emission per ring of shield tunnelling is about 56 t, with material-generated carbon emissions being around 93%, and for the studied case the carbon emission was reduced by approximately 12 000 t(corresponding to the total emissions produced by 200 rings) by means of depth grading and steel-bar reduction; 2) for construction-generated carbon emissions, shield tunnelling in the ⑦2 silty sand layer features high penetration resistance, high cutterhead torque, and highly damaging effects on the slurry, so its carbon emission per ring is about twice of that of the ⑤3 clayey silt layer, and the carbon emissions can be effectively reduced by avoiding a long-distance tunnel buried in the ⑦2 silty sand layer, while the shield advance distance and the buried depth have little effect; and 3) the carbon emissions generated by a one-day stop of shield driving is about 4 400 kg, it is therefore important to improve the advancing efficiency of the shield and to avoid long shield stoppages during tunnel construction. The daily average shield advance rate should be more than three rings—this can reduce the average emissions per ring by at least 60% compared with a one-ring advance rate per day. 2015 Vol. 52 (3): 1-7 [Abstract] ( 3189 ) [HTML 1KB] [ PDF 1023KB] ( 2550 ) 8 On Altitude Coefficient Considering CO from Various Kinds of Vehicles in Highway Tunnels Yan Tao1,2 Wang Mingnian1 Guo Chun1 Yin Jie1 Xie Wenqiang1 As for the current ventilation design of highway tunnels, the value of the altitude coefficient is mainly determined by considering CO emissions in tunnels at low attitudes, while a relevant linear extension is adopted to determine the altitude coefficient for tunnels with altitudes above 2 200 m. With the development of automotive technology and an increase of high-altitude highway tunnels in western China, it is necessary to further study the value determination of altitude coefficients considering CO. In this paper, a calculation formula is deduced for altitude coefficients considering CO from various kinds of gasoline vehicles based on field measurements; this formula provides a relatively accurate way to calculate the required air volume for tunnel ventilation. Using a case study as an example, required air volumes and fan powers are calculated using the code-specified altitude coefficient and the modified altitude coefficient considering CO emissions from various kinds of vehicles, with the results showing that the calculated fan power is significantly reduced using the modified coefficient. 2015 Vol. 52 (3): 8-13 [Abstract] ( 2679 ) [HTML 1KB] [ PDF 823KB] ( 1765 ) 14 Applicability Analysis of the Complementary Ventilation System in Twin-Tube Highway Tunnels Wang Yaqiong1,2 Jiang Xuemeng3 Wu Yigai1 Xie Yongli1 In order to study the applicability of the complementary ventilation system in twin-tube highway tunnels, the effects on the complementary ventilation load ratio and ventilation efficiency are investigated and analyzed in terms of the influence factors, such as altitude, temperature, tunnel length, longitudinal slope, traffic flow, traffic composition and interval between the two tubes. The results show that: the complementary ventilation system should be adopted when the ventilation load ratio between the up-line and down-line tubes is above 1.5, or the absolute value of the one-way longitudinal slope is between 1.5%~2.0%;it is the most economic and practical way to apply the complementary ventilation system in twin-tube tunnels with lengths ranging from 4.5 km to 6 km; the complementary ventilation system should be considered when the mix rate of large vehicles is between 35%~50% based on the influence relation of traffic flow and traffic composition; and the minimum interval for twin-tube tunnels using the complementary ventilation is 30 m. 2015 Vol. 52 (3): 14-22 [Abstract] ( 2766 ) [HTML 1KB] [ PDF 1121KB] ( 2443 ) 23 Rock Classification for Tunnels in High Geostress Areas Yu Li1 You Zhemin2 Chen Jianping1 Sun Yang1 Zheng Wei1 Surrounding rock classification is key for guiding tunnel construction, and its effect on tunnel construction in high geostress areas is fairly significant. Firstly, the influences of the lateral pressure coefficient of the geostress and the included angle between the maximum horizontal principle stress orientation and the tunnel axis on the classification of tunnel surrounding rock are presented in this paper; secondly, the geostress is corrected by increasing the included angle between the maximum principle stress orientation and the tunnel axis; and lastly, based on the Code for Design of Road Tunnels, the sub-classification is supplemented regarding rock masses of grades III, IV and V to achieve a more precise classification of tunnel surrounding rock. Using the Dapingshan tunnel on the Guzhu highway as an example, the surrounding rock classification is corrected by means of increasing the magnitude and orientation of the geostress, with results that are consistent with those of practical excavation. 2015 Vol. 52 (3): 23-30 [Abstract] ( 2608 ) [HTML 1KB] [ PDF 997KB] ( 1900 ) 31 Research on and Control Measures for Base Elevation Variations of Open-Cut Tunnels in Deep Soft Soil Ning Maoquan Base heaving and tunnel settlement due to the excavation and backfilling of open-cut tunnels in deep soft soil have always been of great concern. Using the Wenzhou intercity railway tunnel as an example, this paper studies the issues of base heaving and settlement induced by the excavation and backfilling of open-cut tunnels in deep soft soil. Based on the layer-wise summation method, the value of base heaving after unloading due to foundation pit excavation and the settlement value of a tunnel with a composite foundation after backfilling are studied using the rebound modulus method and the composite modulus method. A comparison analysis of base heaving values and tunnel settlement values under different construction conditions is conducted. The study results show that base heaving of the open-cut tunnel and the settlement of the operated tunnel are controllable, and the vertical deformation decreases and the ground strength improves after applying a composite foundation in deep soft soil. Appropriate control measures against tunnel settlement are adopted considering certain engineering characteristics. 2015 Vol. 52 (3): 31-38 [Abstract] ( 2110 ) [HTML 1KB] [ PDF 1108KB] ( 1696 ) 39 An Active Compensation Method for the Pile Foundation Settlement of an Existing Bridge Influenced by Metro Construction Su Jie1 Zhang Dingli1 Yang Guangwu2 Niu Xiaokai1,2 Zhao Jiangtao1 In response to poor controllability and difficulties with compensating for early settlement by conventional passive protective measures during metro construction beneath existing bridges, an active compensation method for pile foundation settlement of an existing bridge is presented in this paper. The upper and lower structures of the bridge are considered as two separate units—specifically, settlement of the upper part is actively adjusted using the help of an automatic monitoring system to keep it in a safety state by means of determining the rational key technical parameters and applying computer-controlled jacking-up devices. This technique has been successfully applied to the construction of Beijing Metro Line 7 beneath the Shuangjing Bridge. 2015 Vol. 52 (3): 39-46 [Abstract] ( 2486 ) [HTML 1KB] [ PDF 1293KB] ( 1912 ) 47 Assessment and Analysis of the Risks in Whole Construction Process of a Subsea Tunnel Project Li Yongkuan1,2 Zhang Dingli2 Fang Qian1 Compared with other kinds of tunnels and underground works, the subsea tunnel has the features of high complexity, uncertainty and high risk. To ensure the successful construction of a subsea tunnel, this paper systematically analyzed the mechanism for risk occurring in the whole process of subsea tunnel construction, presented the concepts of risk accumulation and risk assessment for the whole process of subsea tunnel construction. The main risk factors were analyzed and identified in terms of subsea tunnel planning, feasibility study, prospective design, bidding and tendering, construction and operation. Based on risk analysis, appropriate risk control measures were presented and successfully applied in the Jiaozhou Bay subsea tunnel in Qingdao. 2015 Vol. 52 (3): 47-54 [Abstract] ( 2269 ) [HTML 1KB] [ PDF 1146KB] ( 1867 ) 55 A Study of Combined Pipe-Roof Scheme Optimization for the Bored Section of the Gongbei Tunnel Pan Jianli1 Gao Haidong2 Shi Peixin3 A pipe-roof combining two kinds of steel pipes with different diameters was recommended in the preliminary design phase for the bored section of the Gongbei tunnel. During the construction design phase, and combining the construction level of the construction unit and the research results of a field pipe test, both the design option and the construction scheme of the pipe-roof were optimized in terms of a unified pipe diameter, section pattern type, launching and receiving of the jacking pipe. Considering the fluid-solid coupling interaction, these two schemes were simulated using the finite difference method. The results show that the unified pipe diameter scheme is superior to the original one in terms of lining deformation, internal force and surface subsidence, and the excavation-induced pore-water pressure drop will generate a consolidation settlement of soil, which is more significant in thawed frozen areas. Through synthetic consideration, the unified pipe diameter scheme can reduce engineering and equipment investments without decreasing the stability and structural safety of the pipe-roof, and it is most feasible in low-risk construction techniques. 2015 Vol. 52 (3): 55-62 [Abstract] ( 2164 ) [HTML 1KB] [ PDF 1262KB] ( 1774 ) 63 A Study of the Interaction Between the Pipes of a Curved Pipe-Roof Li Zhihong1 Li Jian2 Compared with straight pipe-roof jacking construction, curved pipe-roof jacking is more difficult with respect to accuracy control, interaction between pipes and pipe-roof formation. Using the curved pipe-roof jacking of the Gongbei tunnel of the Hong Kong-Zhuhai-Macao Bridge as an example, the interaction between the pipes of a curved pipe-roof is studied using a model test, a numerical simulation and an in-situ test, and the laws and characteristics of the effects of pipe-jacking on the cumulative disturbance of the soil, soil strain, contact pressure between the pipe and soil and the jacking path are analyzed. The results show that: 1) in the process of pipe jacking, the ground surface uplifts and the transverse and longitudinal soil strain increases in front of the jacking machine; 2) the variation laws of soil displacement and strain obtained by the model test are almost consistent with the numerical simulation results; and 3) with the help of effective jacking parameter controls and appropriate construction measures, the interaction between the pipes of a curved pipe-roof can be effectively reduced and controlled by timely measuring and correcting the jacking deviation to ensure successful formation of the pipe-roof. 2015 Vol. 52 (3): 63-68 [Abstract] ( 2167 ) [HTML 1KB] [ PDF 911KB] ( 1790 ) 69 Numerical Simulation of the Groundwater Seepage Field of a Tunnel Group in an Ejective Anticline Zone Zhao Rui1 Xu Mo1 Fan Chenchen2 The ejective anticline is a special geological karst structure found in eastern Sichuan, which may result in engineering hazards and could seriously affect the groundwater environment during tunnel group construction. Since it is difficult to effectively predict the induced variation of a groundwater seepage field by analytical methods, this paper establishes a conceptual model based on the hydrological conditions in the studied ejective anticline zone and predicts variation of the groundwater seepage field using Visual Modflow software. The results show that:1) with the excavation of tunnels, the seepage field changes are obvious and the water level declines sharply, with a maximum drawdown of 48 m and a maximum influential radius of 2.3 km; and 2) after a two-year operation with water being blocked, the water seepage field was almost returned to the normal state before excavation with the water level raised to 1 m below the original level, indicating that the influence of tunnel group construction on the ground water environment decreases gradually. The simulated results are consistent with the measured ones, proving the feasibility of this numerical method. 2015 Vol. 52 (3): 69-74 [Abstract] ( 2554 ) [HTML 1KB] [ PDF 925KB] ( 1791 ) 75 Application of Chaotic Time Series Analysis to the Prediction of Tunnel Surrounding Rock Displacement Chen Siyang1 Zhu Yanpeng2 Huang Lihua1 During tunnel excavation, the surrounding rock displacement inevitably will be affected by many factors. Being a macro representation of the internal mechanical phenomenon of surrounding rock, the displacement possesses strong properties of chaotic dynamics. In this paper, the embedding dimension and optimum delay time are reasonably confirmed based on the one-dimensional data of in-situ measured displacement, and the chaotic time series is reconstructed to fully reflect the phase-space of the original dynamic system. Using the chaotic time series as a training sample, a chaotic time series fuzzy neural network model is set up for predicting the surrounding rock displacement. Surrounding rock displacement of the Zaoshugou No.2 tunnel on the new Lanzhou-Chongqing railway is predicted and analyzed, with the research results showing that the new model has a high precision of prediction, fast calculation rates for convergence and advantages regarding real time and stabilization. 2015 Vol. 52 (3): 75-81 [Abstract] ( 2119 ) [HTML 1KB] [ PDF 964KB] ( 1523 ) 82 Simulation Study on the Deformation and Failure Mechanism of Level Rock in Tunnels Liu Peng1 Ji Feng2 Wen Shuyi1 Based on an analysis of the material composition and structural mechanical characteristics of tunnel surrounding rock, the deformation and failure mechanism of the surrounding rock in a certain tunnel was qualitatively analyzed, the rational test parameters for the base contact friction experiment were determined and an indoor geological model was established according to in-situ stratum bedding and joint occurrences, with the results indicating that deformation of the surrounding rock can be divided into three phases, i.e., bending and inward heaving, tensile cracking, and breaking and collapsing. This was verified for the tunnelling process using a 2D-UDEC numerical simulation, with the results being basically consistent with that of the laboratory model experiment. Thus it is clear that prediction of the deformation behavior of surrounding rock during tunnelling is possible by adopting this indoor model experiment and UDEC numerical simulation. 2015 Vol. 52 (3): 82-87 [Abstract] ( 2080 ) [HTML 1KB] [ PDF 932KB] ( 1719 ) 88 Influence of Tunnel Base Rock Mass Properties on the Dynamic Response of High-Speed Railway Tunnels Ding Zude1 Du Yonggang1 Peng Limin2 Shi Chenghua2 Huang Juan2 Aimed at common problems emerging in tunnel operation, such as softening and disengagement of surrounding rock, and using a high-speed railway tunnel in surrounding rock of grade V as an example, a relevant dynamic response model for multiple working conditions is established. The influences of rock softening and disengagement on the tunnel's dynamic response and operation performance are analyzed based on a concrete damage model and cumulative damage theory. The results show that the applied force of the tunnel deteriorates with the softening and disengagement of bedrock, and its dynamic response indexes, such as dynamic displacement, accelerated velocity, dynamic stress and dynamic damage, increase: of these, the variation of rock mass properties at the tunnel base has the most obvious impact on the vibration response of the tunnel base structure. With the rock disengagement width increasing from 0 to 1.5 m, the maximum increases of accelerated velocity, dynamic tensile stress and dynamic compressive stress are 13.9%, 91.1% and 18.1%, respectively, and the dynamic damage is increased by 17.6 times; with an increase of the rock disengagement width, the fatigue life of the base structure decreases sharply, seriously affecting the tunnel's operation performance. 2015 Vol. 52 (3): 88-94 [Abstract] ( 2107 ) [HTML 1KB] [ PDF 988KB] ( 1531 ) 95 A Study of the Dynamic Response Characteristics of a Tunnel Structure Through an Interface of Soft and Hard Rock Shen Yusheng1 Zou Chenglu2 Jin Zongzhen3 Wang Jingwei1 Tunnel portal sections passing through an interface of hard and soft rock are vulnerable to severe damage at this high intensity seismic area. Based on the Longxi tunnelon the Chengdu-Wenchuan expressway, the earthquake dynamic response of a tunnel portal structure was analyzed using the numerical simulation method for various inclination angles of the soft/hard rock interface. The results show that: 1) the relative displacement of the tunnel lining structure increases obviously during a strong earthquake when the tunnel structure passes through the interface between soft and hard rock, and the relative displacement of the tunnel lining in the diagonal direction is higher than the relative horizontal displacement at the tunnel crown and invert; 2) the relative displacement of the tunnel structure at the soft-rock side of the interface increases with the decrease of the inclination angle, while the earthquake motion has little influence on the tunnel structure deformation at the hard-rock side; and 3) under an inclination angle ＜45°, the earthquake motion has a crucial influence on the safety of the upper tunnel structures (crown and spandrel) with some safety factors being less than 1, and under an inclination angle ＞45°, the seismic motion has a significant effect on the lower part of the tunnel structure (invert and arch springing). 2015 Vol. 52 (3): 95-102 [Abstract] ( 2645 ) [HTML 1KB] [ PDF 1135KB] ( 2285 ) 103 Comparative Study of Earthquake Input Methods for the Seismic Analysis of Underground Structures Wang Jinghe Zhou Xiaojun Mao Lulu Hu Hongyun Considering that the selection of earthquake input methods has a direct impact on the accuracy and reliability of calculation results in the numerical simulation of seismic responses for underground structures, and based on a visco-elastic artificial boundary, this paper analyzes the calculation principles of three input means (acceleration input, displacement input and stress input) and researches the differences among the three methods using ANSYS. The results show that the envelopes of internal force amplitude of the lining are similar, while the numerical differences are quite obvious. A compatible stress input method shall be adopted for the visco-elastic artificial boundary due to the significant effects of different input methods on the efficiency of its energy absorption. 2015 Vol. 52 (3): 103-109 [Abstract] ( 1926 ) [HTML 1KB] [ PDF 1056KB] ( 1670 ) 110 Influence of Metro Construction on the Internal Force of Adjacent Bridge Pile Foundations Zheng Xiguang1 He Ping1 Zhang Anqi1 Li Zhendong2 Liu Zhe1 Wang Xiuying1 This paper studies the influences of urban shield-driven tunneling on the stresses and displacements of adjacent bridge foundations with one, two or four piles using numerical methods. The results show that:1) the axial stress of a single-pile foundation at the side nearest the tunnel decreases while that at the side farther away from tunnel increases, and the influence decreases with an increase of horizontal distance between the pile and tunnel; 2) the axial stress of a two-pile or four-pile foundation at the side nearest the tunnel increases while that at the side farther away from the tunnel decreases; 3) the influence of tunnel construction is greater on the group-pile foundation than on the single-pile foundation, for which the stress difference between the two sides at the top of the pile farther from the tunnel increases significantly after tunnelling, and concrete on the upper part of the pile farther away from the tunnel may be subjected to tensile stress when the pile cap is close to the tunnel; 4) the vertical displacement of the piles decreases with an increase of distance between pile and tunnel, and the settlement induced by tunnelling will be relatively small when the pile bottom is located below the tunnel floor; and 5) tunnelling has the greatest impact on the horizontal displacement of the top of a pile. Specifically, the horizontal displacement decreases linearly with an increase of pile depth when the pile is far from the tunnel, while it decreases nonlinearly when the pile is close to tunnel. The displacement at the upper part of the pile decreases rapidly with an increase of pile depth, and the displacement at the lower part converges to a constant, while the displacement at the top of the pile will peak at a certain distance between the pile and tunnel. 2015 Vol. 52 (3): 110-118 [Abstract] ( 2207 ) [HTML 1KB] [ PDF 1178KB] ( 1495 ) 119 Study of the Interface Mechanical Properties of Concrete Segments in Shield Tunnels Zhao Wusheng1 Chen Weizhong1,2 Yang Fan1 The interface mechanical properties of concrete segments directly affect the stress and strain of the linings in shield tunnels and further affect tunnel waterproofing performance and safety. Therefore, compression and shear tests of the concrete interface were carried out to study the mechanical properties of the interface under different normal forces, different shearing rates and cyclic shearing. The results show that:1) with an increase of normal nominal stress on the interface, its stiffness experiences exponential growth at first, then becomes stable, while the tangential friction coefficient approximately experiences a negative exponential growth; 2) with an increase of the shearing rate, the dynamic friction coefficient decreases at first and later becomes stable; and 3) during cyclic shearing, both the normal stiffness and the tangential friction coefficient of the interface exhibit stability after an increase. Based on the contact mechanics, the normal mechanical model and the tangential friction coefficient model of the interface were obtained by fitting the test results. These results can be used as a reference for the design of segment joints and force analyses of lining structures. 2015 Vol. 52 (3): 119-126 [Abstract] ( 2291 ) [HTML 1KB] [ PDF 993KB] ( 1543 ) 127 Calculation Method for the Passive Limit Support Pressure of an Extra-Large Diameter Slurry Balance Pipe-Jacking Machine in Clay Zhou Shuwei1,2 Xia Caichu1,2 Ge Jinke3 Wang Shuang1,2 Zhang Pingyang1,2 Considering that the support pressure of a pipe-jacking machine must be lower than the passive limit support pressure to ensure stability of the working face, this paper proposes a calculation method for the passive limit support pressure of an extra-large diameter slurry balance pipe-jacking machine in clay based on the ultimate equilibrium of the working face. First, the jacking pipe's passive failure model was studied using anumerical simulation, then a relevant calculation concept was established based on the results and finally the method's rationality was preliminarily verified by the numerical simulation of a practical case. Compared with other methods and based on the analysis of its influence factors, it is indicated that:1) the horizontal cylinder failure mode, which is a passive failure mode and independent of buried depth, is appropriate for the slurry jacking pipe; 2) the proposed method is applicable to the practice for its rationality and simple calculations, of which the application condition for the layered and homogeneous clay simply requires that the working face being kept in a single stratum; 3) the method is more conservative than others, with reasonable lower values; and 4) the obtained passive support pressure increases with an increase of the depth-diameter ratio, internal friction angle and cohesion. 2015 Vol. 52 (3): 127-136 [Abstract] ( 2589 ) [HTML 1KB] [ PDF 1417KB] ( 2493 ) 137 Sungai Buloh-Kajang Line-Underground Package 1 of Klang Valley MRT Project Wen Shuyi1 Liu Peng1 Hu Fan2 Taking the underground package 1 of Kuala Lumpur MRT project as an example, based on 3D Horn's wedge failure mechanism, it adopted limit equilibrium analysis to derive a calculation method for shield chamber support pressures in 3 different cases of full-chamber soil, half-chamber soil or soilless under the acting of earth pressure and full water head pressure, and verified it with the combination of integral analysis and local analysis. The calculation results show that there are totally 5 factors affecting on soil chamber support pressure, i.e. water level, thickness of overburden, cohesion, the internal friction angle of overburden soil and the internal friction angle of soil in working face. Furthermore, a sensitivity analysis of these factors was carried out. It was found that ground settlements have met the design requirements by analyzing the in-situ monitoring data and applying the calculated soil chamber support pressure in construction practice. 2015 Vol. 52 (3): 137-143 [Abstract] ( 2525 ) [HTML 1KB] [ PDF 940KB] ( 1620 ) 144 Static and Dynamic FEM Analyses and Optimization of a Mix-Shield Cutterhead Zhou Yangzong1,2 Nie Yufei3 Li Jie3 Zhang Wei2 Liu Jingzhi3 Guo Jingbo3 The study of force conditions of shield cutterheads can provide a basis for shield type selection as well as the optimal design of cutterheads. Based on the analysis of the force conditions of a shield cutterhead, a static analysis on the cutterhead of a large-diameter shield used in Dongguan city was performed using ANSYS and the stress and deformation of the shield cutterhead in mixed ground were obtained. The vibration performance of the cutterhead was obtained by a modal analysis, and theforce condition of the cutterhead was improved by optimization of the cutterhead structure. The results show that: 1) the maximum stress of this shield cutterhead is 251 MPa during shield construction in mixed ground, which is smaller than the yield limit of 345 MPa; 2) the inherent frequencies of the cutterhead at the first six orders range from 38.803 Hz to 64.842 Hz; and 3) it satisfies the requirements of strength and stiffness, thereby achieving ground settlement control and safety during the tunneling process. 2015 Vol. 52 (3): 144-149 [Abstract] ( 2584 ) [HTML 1KB] [ PDF 934KB] ( 2527 ) 150 Field Monitoring and Analysis of the Influence of Shield Tunnelling for the Huangzhou Metro on Existing Buildings Wei Gang1 Ye Qi2 Yu Xingfu1 Using the double-tube shield tunnelling of Hangzhou Metro Line 1 that passes beneath buildings as an example, field monitoring was performed and relevant analyses were made regarding the measured settlements of existing buildings and ground surface in combination with shield driving parameters; the settlement rules of different positions and buildings induced by the double-tube shield tunnel construction were researched. The results show that: 1) building settlement can be effectively controlled by managing the volumes of grouting and soil extraction; 2) the larger the base area of a building, the more variable the settlement curve of the monitoring point, which requires strict control of the construction process; and 3) the closer the horizontal distance between the buildings and tunnel axis, the more approximate is the settlement rule of the monitoring point to that of the ground surface above the axis. 2015 Vol. 52 (3): 150-159 [Abstract] ( 2127 ) [HTML 1KB] [ PDF 1420KB] ( 2175 ) 160 A Study on the Ground and Building Settlement Caused by Shield Tunnelling in a Peat Soil Stratum Zhou Jiamei1,2 Meng Guowang1,2 Yan Qi1,2 Xie Qubo3 In this paper, using the Kunming Metro as an example, the effects of shield tunnelling in a peat soil stratum on ground and building settlement are studied using a numerical simulation method. The results show that: 1) advanced compression and settlement of the peat soil are induced by the construction load; 2) the influence range of ground heaving in the longitudinal direction is nearly 2~3 times the tunnel diameter, while the influence range of settlement in the horizontal direction is nearly 7 times the tunnel diameter, with maximum settlement occurring in previously constructed tunnels; 3) the ground settlement becomes stable 30 m behind the excavation face; and 4) ground and building settlement is mainly induced by previously constructed tunnels, within a range of 20 m on both sides of the tunnel axis, which leads to the building inclination and tensile failure of the substructure. Therefore, countermeasures should be adopted to reduce such building damage according to ground deformation laws and the relative position of buildings and previously constructed tunnels. The ground and building settlement laws are verified by field test data. 2015 Vol. 52 (3): 160-167 [Abstract] ( 2450 ) [HTML 1KB] [ PDF 1161KB] ( 1816 ) 168 Excavation Schemes for Eight Pilot Tunnels in the Daguanying Subway Station on Beijing Metro Line 7 Tan Wenhui Sun Hongbao Xu Luheng The construction of the Daguanying subway station on Beijing Metro Line 7—beneath heavy traffic on Guangan Avenue and adjacent to a pedestrian overpass—features a large excavation cross section, complex soil conditions and numerous underground utilities. In order to guarantee safe construction and normal operation of municipal infrastructure, FLAD3D software was used to establish a model for the pilot tunnels and a comparison study of the excavation schemes for the pilot tunnels was carried out. The results indicate that the settlements at the crown, utilities and ground induced by excavation of the upper pilot tunnel first were less than those induced when excavation of the lower pilot tunnel occurred first; the stress distribution on the lining was also more reasonable for the former, so the scheme of excavating the upper pilot tunnel first was selected. Dynamic monitoring of the settlements at the crown, utilities and ground was carried out during excavation of the pilot tunnels and the real-time monitoring results are nearly consistent with those of numerical simulation, which indicates the rationality and feasibility of this numerical analysis. 2015 Vol. 52 (3): 168- [Abstract] ( 2201 ) [HTML 1KB] [ PDF 1072KB] ( 1457 ) 175 Calculation Method for Surrounding Rock Pressure of a Loess Highway Tunnel with an Extra-Large Section Wang Chunhao Using the construction of the Tangjiayuan tunnel in loess with an extra-large section as an example, the surrounding rock pressure is calculated by five common methods, of which the results from the Terzaghi theory-based method were very consistent with the measured data. A correction method is put forward regarding the lateral pressure coefficient, and is recommended for application to the Tangjiayuan tunnel. Furthermore, in light of the definition criterion between the shallow- and deep-buried tunnels, a simulation method is also proposed for determining the boundary of the shallow and deep depths based on the variation rule of the lateral pressure coefficient of the soil body on the centerline, the Tangjiayuan tunnel is considered to be shallow-buried, with a boundary of 90 m. 2015 Vol. 52 (3): 175-181 [Abstract] ( 2435 ) [HTML 1KB] [ PDF 944KB] ( 2449 ) 182 Discontinuous Deformation Analysis for an Underground Cavern Group with Stepwise Support Wang Wen1, 2 Zhu Weishen1 Zhang Dunfu3 In this paper, an existing discontinuous deformation analysis program was improved using the aspects of stepwise support and relevant convergence criterion. The stability of an underground cavern group with random joints in a large hydropower station was analyzed by the improved program, especially in terms of the effects of construction factors and the stepwise support, and it was verified by comparing the analyzed results with the measured ones. Through a comparison of the influence of various excavation sequences of the three caverns (main powerhouse, transformer chamber and tailrace surge chamber) on rock stability, an optimization was carried out for the support scheme based on the deduced depths of the failure zone and the displacements of key points, showing that the optimal excavation sequence is to excavate the main powerhouse and the tailrace surge chamber first and then the transformer chamber; the cable bolting may be additionally installed at key parts of the tailrace surge chamber to improve the stress state of the surrounding rock. 2015 Vol. 52 (3): 182-188 [Abstract] ( 2103 ) [HTML 1KB] [ PDF 1013KB] ( 2402 ) 189 Optimization of Tunnel Overbreak Prediction Based on Geological Parameter Analyses Lu Zhongle1,2 Wu Li1,2 Li Bo1,2 Zhang Xuewen1,2 Considering that overbreak of rock may cause construction cost increases, large deformation or even tunnel collapse, and using the Mingshan tunnel as an example, this paper analyzes overbreak characteristics and establishes a prediction model. Using the blasting parameters as a constant, the effective geological parameters as an input and the actual overbreak volume as an output, three prediction methods are compared: the Fisher Discrimination Analysis Method(FDA), the Conjugate Gradient Method(CG) and the Support Vector Machine Method(SVM). The results show that their correlation coefficients R2 are 0.694, 0.718 and 0.947,with the correlation coefficient of the SVM model being the highest and the CG model coming second. The SVM model has sound prediction precision and adaptability even at the data point where abrupt change occurs. Adopting the SVM model can result in optimal quantitative prediction with high precision, while adopting the CG model can provide rapid and simple prediction with controllable precision. 2015 Vol. 52 (3): 189-192 [Abstract] ( 2624 ) [HTML 1KB] [ PDF 623KB] ( 1729 ) 193 A Study of the Construction Sequences of a Large-Section Shallow-Buried Unsymmetrical Loading Tunnel by the CRD Method Shi Xiong Zhang Jiasheng Liu Baochen Using the Liangcun tunnel constructed with the CRD method as an example, the surrounding rock deformation and structural internal force characteristics are analyzed for tunnels constructed by the CRD method by installing deformation monitoring points and internal force testing elements. The surrounding rock displacement and stress variation under different excavation sequences are analyzed and compared by numerical simulation of the excavation process for a tunnel constructed using the CRD method. The results show that the CRD method has a great impact on the construction sequence of each construction part, while the magnitude of impact by each construction part on crown settlement are (from high to low): part one, part two, part three and part four. Rock pressure at the internal side of the mountain is larger than that at the outer side, and all the internal force of the steel brace is compressive stress with the maximum axial force located at the haunch. By comparing the deformation differences caused by tunnel excavation and the structural loading features, and based on a numerical analysis, it is concluded that first excavating a partial section at the outside of the mountain has great advantages in terms of surrounding rock deformation, structural stress and safety factors. Thus, the reasonable construction sequence is to first excavate the partial section outside of the mountain with primary support installation and then to excavate the other section inside of the mountain. 2015 Vol. 52 (3): 193-199 [Abstract] ( 2523 ) [HTML 1KB] [ PDF 969KB] ( 1803 ) 200 Treatment of Bed Waterlogging and Track Heaving in Tunnels on the Xiangtang-Putian Railway Xiao Guangzhi Xue Bin Aimed at the problems of bed waterlogging and track heaving in the Xuefengshan tunnel and three other tunnels on the Xiangtang-Putian railway, this paper analyzes relevant causes and proposes a treatment scheme based on the principle of "pressure reduction by water discharging, tunnel bottom reinforcement and returning of water flow to channel," showing that the track elevation returned to a normal level at the heaved section and the bed structure became stable after fine adjustments of the ballastless track with no water inside the bed or with little water left after the flow returned to the channel. Suggestions are made, including improving tunnel waterproofing and drainage designs and enhancing construction technology control and quality assurance regarding defects such as cracking and heaving of ballastless beds induced by water seepage or confined water at the tunnel bottom. 2015 Vol. 52 (3): 200-204 [Abstract] ( 2276 ) [HTML 1KB] [ PDF 717KB] ( 1672 ) 205 Failure Mechanism and Control Measures for Gas Bursts in Gas Tunnels Huang Xiongjun Considering that gas bursts are very detrimental to tunnel construction, and using a railway tunnel with such a risk as an example, this paper discusses the failure mechanism and relevant prevention and control measures from the aspects of advance geological prediction, gas monitoring, construction ventilation and coal disclosing technology. Results show that: 1) gas burst—the result of multiple factors, including of the outburst of coal, rock, gas and stress field—is a complex dynamic phenomena, for which the elastic strain energy of the coal and rock and the internal energy of the gas are the bursting energies and the geostress mutation and construction disturbance are the incentives; 2) gas bursts are easily induced at the weak point or surface of the working face, especially during construction disturbances with poor prevention; 3) a comprehensive advance geological prediction system, dominated by advance horizontal drilling, deepened hole detection and gas measurement and various physical exploration methods, is an important means to prevent gas bursts; and 4) with the help of a safety standard management system, construction risks can be effectively avoided by adopting technical measures like gas emission, coal disclosing, construction ventilation and structural treatment. 2015 Vol. 52 (3): 205-210 [Abstract] ( 2326 ) [HTML 1KB] [ PDF 949KB] ( 1624 ) 211 A Study of Construction Risk and Countermeasures for Shield Tunnelling Under Urban Buildings Zhang Tuanjie1 Wang Yuanping2 A risk assessment and corresponding treatment are carried out for the special working conditions regarding shield tunnelling under houses for the Wuxi Metro Line 1(from the College town station to the Xuelang station). There are two problems that need to be solved: 1) the passage under the houses, for which the earth pressure intensity shall be calculated and backfilling shall be adopted for the deep well, which may breakdown under the grouting pressure; and 2) maintaining construction safety during tunnelling under the old houses, whose foundational structures, service conditions, safety performance and controllable settlement shall be investigated and evaluated. For these problems, such construction countermeasures as uniform and continual shield driving, less correction of alignment deviation and regular monitoring are presented. The results show that these countermeasures are feasible and appropriate for the requirements of construction safety, including calculation of earth pressure intensity, control of shield tunnelling parameters, shield attitude adjustment and monitoring and measurement; when the shield passed beneath the houses, no danger occurred and the maximum settlement was 8.2 mm. 2015 Vol. 52 (3): 211-215 [Abstract] ( 1985 ) [HTML 1KB] [ PDF 785KB] ( 1679 ) 216 Experimental Study of Tunnelling Technology Combining a Boom-Type Roadheader with Smooth Blasting Xie Dawen As a soft-rock shallow-buried tunnel passes through urban areas, surrounding residential buildings are disturbed and even damaged by vibrations that occur during blasting construction, and therefore, special damping measures are needed. Using the new Hongyan tunnel on the Chongqing hub railway as an example, tunnelling technology that combines a boom-type roadheader with smooth blasting is studied based on such mechanical equipment as the boom-type roadheader and milling machine adopted in tunnel construction. The results indicate that this combined boom-type roadheader and controlled blasting excavation method apparently reduces the construction vibrations and is applicable to the construction of tunnel sections with an overburden of 15~20 m, while a half-section fully-mechanized excavation method is suggested for the construction of tunnel sections with an overburden of less than 15 m. 2015 Vol. 52 (3): 216-220 [Abstract] ( 731 ) [HTML 1KB] [ PDF 717KB] ( 2364 )

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