Applied Mechanics and Materials Vols. 405-408

Abstract: To address the problem of sluice concrete easily cracking during construction, this study introduces the crack mechanism of concrete structures. Temperature differences and constraints are the main causes of cracks. Anti-cracking measures should focus on optimizing concrete mixing ratio and improving construction technology. Using simulation calculation to model the actual construction process and temperature control measures, this study analyzes the causes of crack and selects timely and reasonable temperature control measures, which are necessary links in engineering construction. A three-dimensional finite element analysis was conducted for a huge concrete sluice structure. The causes of cracks are discussed, and timely and feasible anti-cracking measures are proposed to provide technical support for project construction.

Abstract: To research the local stress state of the polyline pretensioned beams, the 3-D nonlinear finite element model is established by FEA software ANASYS. The results show that the existence of the inflection point on the prestressed reinforcement is the main reason of local stress distribution, and the corner radius R is the primary influential factor of the local stress distribution phenomenon. Then, the variation law of the stress and stress distribution by the corner radius R is illustrated clearly. With the increasing of R, the maximum local stress has decreased, and the stress distribution curve has increasingly become smoothly and gently. Considered the variation law of local stress and various of construction requirement in engineering practice, R=600mm is selected as the optimal radius.

Abstract: The surrounding rock strain field monitoring have been done during a highway tunnel excavation. The rock rheological parameters was inversed by neural network based the field monitoring data. The predicted value and the field monitoring data have been compared, the result shows that the difference is 12%, the predicted value is credible.

Abstract: Through the elaboration of the management towards the whole process of preliminary feasibility demonstration, planning of design, construction process and completion settlement about Hangzhou subway construction project, the paper summarizes and analyzes the conditions of subway construction project in the aspect of investment control management, in addition to the analysis of the reasons for some problems occurred and finally puts forward some measures and suggestions to improve the investment control management of subway construction project with an aim to enhance the ability of investment control management towards the subway construction projects in Hangzhou and other domestic regions.

Abstract: In case of poor surrounding rock conditions, multiple-section blasting method is usually used in large-span tunnel. The sprayed concrete in tunnel will receive multiple blasting effects from different blasting section. Hence, its valuable to research the safety of sprayed concrete lining. Based on the field observation data and construction condition in Shizilong tunnel, The relation between initial velocity and crack length of different concrete age is obtained through indoor tests and the velocity is calculated when the length is 2mm. Then, with the mechanics theories of fracture and damage, the cumulative damage of rock and concrete is studied microcosmically and the increment expression is mended at the same time. The accuracy is verified based on a large number of data in the end, which is helpful for construction of large-span tunnels in future.

Abstract: The prediction of ground collapse caused by subway shield construction has been an important technical problem in urban subway shield construction, if the ground collapse could be pre-estimated, it could be able to take appropriate precautionary measures in advance to avoid the occurrence of ground surface settlement before the project construction, but it’s difficult to predict and calculate the settlement accurately. This paper analyzed main causes of ground collapse caused by shield construction, summarized the influence of several important parameters to surface settlement and then Midas GTS 3D numerical simulation software was used to simulate shield construction process and calculate ground surface settlement, to calculate stress, strain and displacement of overlying strata above the shield driving machine, obtained calculated values of surface settlement to predict ground collapse. Practice has proved that this pre-estimation new technology is in accordance with fact, it provides a useful reference for subway shield construction project.

Abstract: Supper-deep diaphragm wall construction of a Tianjin traffic hub project penetrated through many soil layers and two layers of confined water, geological and hydraulic conditions were complicated. Some special technologies including grooving methods,anti-collapse measures,verticality controlling measures, joint treatment measures and steel reinforcement cage hoisting measures were adopted for the construction. The project was finished with short time, low cost and good quality. Engineering practice shows that these technologies were appropriate for constructing supper-deep diaphragm wall under complicated geological and hydraulic conditions. These experiences can give some references to the similar super-deep diaphragm wall construction of Tianjin and other regions in future.

Abstract: The 1.39km long tunnel in Shouyi Square of Wuhan is situated at the main artery of the city traffic. To ensure smooth construction of this tunnel project, a varieties of supporting systems such as rubble retaining wall, piles and steel supports, cantilever piles, pile-anchors, shotcrete-bolts are adopted. Meanwhile, safety monitoring is carried out using advanced monitoring instruments and methods with emphasis on the key cultural relic of Hubei province Honglou. The influence of the foundation excavation construction on Honglou is informed by analysis of monitoring result and the monitoring prediction provides forceful support for decision-making during the construction. In this way smooth construction of the foundation excavation and safety of Honglou are ensured.

Abstract: The 3D finite element simulation was adopted to study the globality stability of tunnel caused by the different excavation length of invert. Kelan-Linxian highway loess tunnels were taken as an example. The research results are shown as follows: The vertical displacement and horizontal convergence increased by the increasing of the excavation length of the invert. But the latter increase range is larger than the former. The horizontal convergence in sidewall is convergence value is greater than the level of the arch and the corner, the horizontal displacement primarily occurred in the side wall position. The surrounding rocks maximum plastic strain occurred in side wall and corner wall in 4 working conditions. The plastic zone occurred around from arch corner to wall side. In Tab. 4, the maximum plastic strain is increased by the excavation length of inverts increasing.

Abstract: The ABAQUS software was used to establish an actual soil layers-tunnel model in which the infinite element boundary was adopted. Then, frequency domain analyses were conducted on the model under vertical train loads with different frequencies. The attenuation of the vertical displacement amplitude on ground surface under each load was computed in the area ranging from 0m to 30m. The results show that the displacement amplitude may rebound in a particular area under some loading frequencies and this phenomenon is closely related with the loading frequency.