According to Rabcewicz (1964, 1965), tunnels should be driven full face whenever possible. The pre-cutting method is a popular tunnelling method based on this idea. This method allows safe excavation even in poor ground conditions by creating continuous pre-arching around tunnel periphery in advance. Because of high costs and safety risk in field test, the previous studies on pre-cutting method are limited and qualitative, which mainly focused on its machine, construction procedure and applicable conditions. To further develop this method, systematic and quantitative studies on ground settlement and pre-arching stress caused by it are needed. In this study, a 1:10 geo-mechanical physical model test was performed to understand the mechanism of pre-cutting method by simulating its construction process. The ground settlement, earth pressure and pre-arching stress during tunnelling were investigated. Afterwards, three-dimensional numerical simulations were performed to simulate the process of physical model test so as to compare with experimental results. The effects of different pre-cutting parameters such as length, thickness, lap length and sequence of cutting slots, which can’t be sufficiently covered by the model test, were studied by numerical method. Comparative studies between pre-cutting and New Austrian Tunnelling Method (NATM) under the same geological conditions were also carried out. In general, the comparative analysis shows that the physical model test has achieved satisfactory results and the pre-cutting method has a great advantage in controlling ground deformation compared with NATM.

In the case of a shield tunnel construction in Beijing, on the basis of the interaction mechanism of neighborhood tunnels during tunnel excavating, a 3D nonlinear numerical simulation model was set up. The developing laws of the segment lining stress, ground deformation around tunnels, segment lining deformation, and changing bending moment of segment lining in different tunnel spaces are analyzed in detail. The results show that the stress growth rate of segment lining and tunnel space are linearly descending related to the situation of the immediately adjacent shielding. The ground settlement form is similar to the case of the single-tunnel construction due to space constraint. Furthermore, it is found that the form is single mode. Under horizontal compression and vertical tension, the segment lining deformation is in ellipse deformation trend. The response of the left existing tunnel to adjacent shielding has hysteresis effect. The result shows that 3D numerical model is a useful method, which can directly display the interaction law of neighborhood tunnels during construction. The study results can be used to guide the construction of immediately adjacent shield tunnels.

以北京地区大断面地下人行通道工程近距离上穿最小净距仅1.97 m的地铁10号线盾构隧道为背景,采用浅埋暗挖CRD法上穿盾构隧道施工,根据工程特点,分别对东线和西线隧道结构竖向位移、隧道结构水平收敛位移及道床结构竖向位移3种变形进行监测、分析.现场实测结果表明:(1)大断面通道上穿施工引起的既有地铁隧道结构变形以上浮为主,隧道结构竖向位移为-0.10～4.10 mm、水平收敛位移为-0.03～-1.80 mm、道床竖向位移为-0.30～2.90 mm,隧道结构与道床结构变形协调.(2)隧道结构竖向位移、水平收敛位移及道床结构竖向位移的变化规律一致,均经历了快速上升区、急速回落区、波动下降区及后期波动稳定区4个阶段.在通道掌子面开挖通过盾构隧道后,隧道结构的上浮变形速率明显加大,呈现陡升趋势;通过通道底板向下注浆后,隧道的整体上浮受到明显控制;向下注浆结束后,隧道的上浮变形速率已趋于平缓;通道二衬结构完成后,由于上部荷载的增加使得隧道整体变形呈波动下沉,并最终趋于稳定.可见,通道内注浆对于控制盾构隧道结构上浮作用明显,为今后类似工程提供借鉴.

Numerical simulation analysis method is empoyed to study the mechanical behaviors of segments of connecting passage of a shield tunnel. The general construction method and process of the connecting passage are introduced. Through field monitoring analysis and three-dimensional finite element analysis, the force and displacement characteristics of the get the contact channel, segments during construction of the connecting passage and after hole-opening are obtained. The results show that during: construction of the connecting passage and after hole-opening, the horizontal additional displacement of the shield segments is generated, towards the direction of the connecting passage. Owing to the construction of the connecting passage, the original forces of the segments lead to stress redistribution of the Most of the segments at the side openings will produce negative tension forces, and it will seriously affect the safety of the shield tunnel. To this end, temporary support reinforcement measures for the shield tunnel segments are proposed. This study has the reference value for similar projects.

Based on the construction of deep foundation pit in Beijing, according to the actual construction process of supporting structure, the beam calculation model was used for excavation and support of the deep foundation pit. In the pit, piles and internal bracing were used as the enclosure structure. The interval force and deformation of supporting structure were discussed. According the calculations of numerical modeling, the variable law of horizontal displacement, bending moment and axial force in the pile body was analyzed. It was comparative analyzed between the monitoring data and the calculated values of y horizontal displacement and bracing axial force in the pile bod. The results show that: (1) the maximum horizontal displacement of pile increases with the increase of excavation depth and time, and maximum horizontal displacement of points moving gradually to excavation face. The horizontal displacement reached a maximum value when the excavation at the bottom of the pit. (2) while the axial force is a reflection of the pressure of behind the supporting structure, but the axial force was not increased with the depth of bracing. (3) comparative analysis result of field monitoring shows that the variable law of values calculated by the numerical simulation results well agrees with the measured data.

Based on the construction of deep foundation pit in Beijing, according to the actual construction process of support structure, two different numerical simulation models are constructed separately for the diaphragm wall and the bored pile. The interval force, deformation of diaphragm wall and bored pile were discussed. Through comparison of surrounding surface settlement, horizontal displacements of support structure, bending moment of support structure, axial force of bracing, and stability of foundation pit in different case obtained from the simulation model, the performances of these two methods mentioned above were analyzed. It is shown that the diaphragm wall is more effective than bored pile in controlling the displacement and the proper stress of piles.

Generally the tunnel construction in downtown area is restricted by high-density buildings, narrow site space, complicated geotechnical condition, dense underground networks and busy traffic. The double or multiple tunnels are frequently used in processing subway engineering in cities. Sometimes underground space construction must be done close to the existing tunnels with complicated mechanics behavior. With the increasing adjacent-tunnel engineering by shielding, problems of interaction induced by nearby-neighbor shielding tunnel become more and more serious. Therefore, controlling the effect of clear-distance shielding tunnels can ensure the safety of existing shield tunnels and successful construction of new shield tunnel, which is very important to the development and utilization of urban underground space. In this paper, an overall analytical study was made on the neighborhood effects during the nearby-neighbor tunnel construction with shield driving method. On the basis of summarizing the current studies, some typical practical cases and treatment methods were introduced, some key problems encountered in the present studies are put forward, and some new ways for research in future are expected.

Based on a certain constructing running shield tunnel of Beijing metro side-crossing close to a high-rise building,using the finite element method calculation model and site monitoring method,the foundation characteristics of the high-rise building affected by the constructing shield tunnel are studied. In different construction stages,the variations of the foundation settlement and inclination of the high building are analyzed. The simulation results show that stratum vertical displacement has a sudden change near the high-rise building. Away from the building in an enough distance,the displacement curve becomes flat. From site monitoring results, the high-rise building inclined to the direction away from the tunnel prior to the shield closing to the building, while the building inclined towards the tunnel during shield crossing. The settlements of the monitoring points reach the maximum value when the shield is 10.0 m away from the monitoring surface. However,the settlements declined significantly when the shield is more than 60.0 m from the monitoring surface,and finally becomes stable. The simulation and the site monitoring results agree well. The conclusion would be helpful for the future similar shield tunneling projects.

Due to the continuous development and utilization in urban underground space, the spacing between adjacent tunnels in new projects is becoming smaller and smaller in constriction of the surrounding buildings. In case of a shield immediate adjacent double-line tunnel construction in Beijing subway, a three-dimensional (3D) nonlinear numerical simulation model to simulate earth pressure balance (EPB) shield tunnelling was set up. The developing law of the stress and deformation of the adjacent existed tunnel in variable tunnel spaces are analyzed in detail. The results show that the segment lining deformation is in ellipse deformation trend under horizontal compression and vertical tension. The simulation results obviously demonstrate that the deformation growth rate of segment lining is less than the stress growth rate of segment lining. The results also describe the sensitivity of the stress of segment lining to the variation of tunnel space. In plastic zones connected around double-line tunnel, the plastic zone form is similar to the case of the single tunnel construction due to very narrow tunnel space. The 3D numerical model directly displays the interaction of immediate adjacent tunnels during construction, therefore, it can be served as references for project design and the construction of adjacent variable spacing shield tunnels in future.

选择21日龄约克夏仔猪24头(公母各半),采用随机配对,分为对照组(基础日粮)、在基础日粮中添加溢多酶复合制剂的试验A组(180mg·kg-1)和B组(150mg·kg-1),每组8头,经过27d饲养试验,分析溢多酶对仔猪生产性能、腹泻和经济效益的影响。结果表明,试验A组和B组仔猪日增重比对照组分别提高17.2%(P<0.01)和13.7%(P<0.01),饲料效率提高16.6%(P<0.01)和13.7%(P<0.01),饲料成本分别降低2.5%和2.2%,平均每头仔猪节约饲料费用7.45元和6.56元,经济效益显著,且仔猪腹泻率随溢多酶添加量的增加呈现下降趋势。

For a certain deep foundation pit of Beijing Olympic Park,the beam calculation model was used for excavation and supporting of the deep foundation pit.In the pit,the piles and earth anchors were used as the supporting structure.The principle of bar system finite element method could effectively take into account the influences of various factors and complex situation during the course of excavation on interval force and deformation of supporting structure.According to the calculated results, for the horizontal displacements,bending moments and shear forces of the fence piles as well as the horizontal pull forces of the earth anchors,the analytic results were given with the increasing depth of excavation on earth change.It is shown that the supporting structure is effective in controlling the displacement of strata around the foundation pit and the proper stress of piles.

In the paper,test principles and method of installation of the steel string strain gages are introduced.Steel string strain gages were installed in the segments in order to monitor the stress variation in the segments due to the excavation of a cross passage in a Beijing subway shield tunnel.Monitoring data provided assurance for the construction region and environment around the project.At the same time,statistical analysis was applied to the monitoring data.By comparing the stresses in the concrete segments with those in the neighboring steel segments,the stress variation in the shield tunnel segments due to the construction of the cross passage was revealed,and thus paved the way for the smooth completion of the project.

The immunization against steroid hormones could improve the fertility of female mammals. The present study was to investigate the effects of TIT on the fertility in Huanghuai White goat. Twenty healthey she-goats,2-2. 5 years old . 20~25kg weight, were equivalently divided into two groups at random. One group were administrated hypodermically with 1ml TIT, whose active ingredient is Testosterone-3-Carboxymethl-Oxime-Bovine Serum Albumin . And this injection was repeated once 3 weeks later. As the same way, the control was treated with 1ml physiological saline twice . The results show that the active immunization against TIT significantly improve (P0. 05) the birth rate (treated group vs control, 383. 3±61.1% vs 283. 3±55. 6%). The rate of survival lamb however, has no signifi cant difference (361. 7±55. 6% vs 266. 7±66. 7%),P0. 05. The administration could enhance the rate of survival lambs by 18. 7%. The treatment of TIT has no statistically significant effect on gestational periods and the survivallambs' weight (P0. 05). it is also found that there is significantly negative correlation between the litter sizes and the gestationsl prtiods(r=- 0. 6114. n = 12).