Applied Mechanics and Materials Vols. 90-93

Abstract: The increase in axle load and speed, the worse of service environment and the deterioration of existing bridges result in various of damages in structures. In order to ensure the safety of the structure, it is essential to assess the performance of the structure. In this paper, based on the frequency changes of the damaged and undamaged structure, damage positioning indicator method was used to locate the damage of the structure. Damage assessment method (SSZD) based on modified modal strain energy method was used to assess the extent of structural damage. The results show that this method can be used to locate and assess the structural damage accurately.

Abstract: The length of Shijiazhuang Railway six-line tunnel(Beijing-Shijiazhuang Passenger line) is 4980m, cut and cover excavation method is used widely. The width of pit is 30~52m and the depth is 8.5~22m. In order to use large machine, cable support structure is used. The west side of pit is Beijing-Guangzhou Railway. The nearest distance from pit is only 10.2m. The cable properties will change because of the train vibration. Therefore, the scope of the train vibration, vibration velocity, anchor axial force and horizontal displacement of pile are measured to get the influence of the train vibration, which can provide basic data for design and construction.

Abstract: The function of vc++ is powerful, and the application of its serial communication technology is more and more extensive. This paper introduces the settlement monitoring system first, and then focuses on the application of vc++ serial communication technology and real-time data monitoring technology in the subsidence monitoring. Next we debug the system and draw the final conclusion: using computer and wireless communication technology can successfully achieve the accurate monitoring of the remote settlement.

Abstract: It is often necessary to study on the seismic performance of the buried pipelines subjected to tunnel excavation, because the ground motion will inevitably endanger the nearby underground pipelines. In this paper, modeling and analysis of earthquake-resistant performance of tunnel excavation to the upper underground pipeline have been carried out. The changes of stress and displacement of the upper underground pipeline under action of the same seismic wave before and after tunnel excavation was compared. It is showed that there’s a greater impact on the stress and displacement of upper underground pipeline under seismic action, and a tunnel with reasonable supporting would support the underground pipeline to some extent.

Abstract: The yanmiao bridges are used in the 32m prestressed concrete simply-supported box girders on the wuhan-guangzhou passengers dedicated line,they are constucted in the mobile form.To ensure the constuction safety and the accurated line,static load test and monitor for the mobile form were did.The result of test and monitor showed that in the state of work the different parts’force of the mobile form is in the elastic range. The entire beam deflection curve linear is reasonable, they provided the test reference for the the setting of the pre-camber and the control of the box girder’s height.

Abstract: In order to study and demonstrate the safety condition of urban track transportation system in mechanics area, and to determine the key points and difficulties of this system, it uses FLAC3D numerical simulation software, combines the applied examples of engineering projects, carries on simulation analysis on aspects of surrounding soil’s deformation rule during construction stages, the mechanics analysis during main structure’s construction, and the system surrounding soil’s stress-strain rules during operation stages, etc.. Feasible safety measures and suggestions were proposed accordingly. The applied research indicates that the numerical simulation analysis can express the risk characteristics and rules well during engineering construction and after construction, and further avoid potential hazards or accidents’ occurrence, which has important meanings for ensuring the safety of engineering projects during the whole process.

Abstract: Abstract: Conducted a series of triaixl coupled consolidation and creep tests ,and researched the coupled consolidation and creep character for the typical soft clay in Wuhan region in different drainage conditions.The following conclusions are got from analysing the stress、strain and time relationship curves in different conditions:(1)The consolidation drainage condition is very important in the soil consolidation creep deformation.When the stress is low,the deformation amount in the consolidation undrained condition is much smaller than that in the consolidation drained condition;with the increasing of the stress,the viscoplasticity will appear,and the deformation speed in the undrained condition exceeded that in the drained condition;when the stress increases to some point,the deformation amount in the undrained condition will exceed that in the drained condition finally.(2)The consolidation creep deformation rule for the typical soft clay in Wuhan region in different drainage conditions can be expressed by empirical formula.

Abstract: The Wushaoling tunnel passes the active engineering fault 7(simply called F7 below), where the surrounding rock is broken, mainly composed of fault boulder clay and rubble with very low strength/geostress ratio, resulting in remarkable deflection. Measures have been taken to control the large deflection of the primary support effectively and to ensure safety of the lining structure so that the F7 can be passed as early as possible . Two small-section roundabout drifts for left and right line each, affected less by the high geostress, are excavated in order to continue the construction ahead, to release partial geostress and to conduct experimental study guiding the design &construction of the main tunnels. At the same time, in-situ experiments are carried on against different pattern and parameters of support structure. Based on the above study, the measures are finally determined such as adopting circular multiple-support composite lining, setting deformation joints per segment to absorb the movement of the active fault, adhering the construction principle of “rapid excavation, rapid support, rapid closure and timely lining”, etc. As a result, the large deflection is controlled effectively in subsequent construction and the large-scale active fault rarely encountered domestic and abroad has been passed successively.

Abstract: Based on the 1# shield tunnel of SU ZHOU rail transit, a 3D discontinuous contact computational model of shield tunnel segment and bending bolts is built. This paper study about the stress and the deformation of shield tunnel segment with actual loads ,and the influences on shield tunnel segment by properly install the bolts. Result shows that timely apply pre-stress on the bolts could effectively decrease the deformations on segment joint by the shear resistance capacity of the bolts. The maximum deformation reduces from 3.580mm to 0.302mm. And there appear an open-angle which turn to outside or inside on segment joint. The maximum spacing of the open-angle is 0.66mm, and the maximum angle is 0.108 degree. In most position about shield tunnel segment, installed bolts reduced the axial forces and increased or reduced the bending moments.

Abstract: CRD method and three-bench method with temporary invert, which are applied to shallow buried and large cross-section tunnel engineering, are discussed, and simulated by FLAC2D so as to study the variation feature of displacement field, surrounding rock disturbance and internal supporting force caused by the excavation. According to the simulation results, it is proved that CRD method, with higher safety, can control tunnel collapse effectively while three-bench method quickens construction schedule. Therefore, it is recommended that the two methods are used for excavating tunnels alternately if possible so that it will increase economic benefit.