Advanced Materials Research Vols. 243-249

Abstract: The self-developed finite element program on return mapping algorithm is used to the simulation of the true tunnel with C + + language, while the finite element program is embedded into differential evolution algorithm to achieve the inversion parameter. Applying to Line 1 of Dalian Metro, rock mechanics inversion parameters and true parameters are close, which indicates the superiority and good prospects of return mapping algorithm and different evolution algorithm, and it can be used for quantitative analysis of actual tunnel.

Abstract: The key problem of supporting structure design is the load calculation in tunnels with shallow buried depth and unsymmetrical pressure in the situation of weak surrounding rock. The results of simplified calculation method recommended by Code for Design of Road Tunnel differ from the practical situations to a certain extent because of the neglect of load calculation range that makes the results less than the practical values, which will bring about potential safety hazard. Based on the calculation method of the Code, modified computational formulas of vertical load of internal and external sides and horizontal load are put forward based on new assumption conditions and load simplified model. The modified formulas were adopted in the calculation of the entrance of Huo-Cheling Mountain Tunnel with unsymmetrical pressure, and the results were compared with those obtained by the method of the Code and numerical simulation. The comparison show that the results of modified formula coincided with those of numerical simulation, while the values calculated by the Code were smaller.

Abstract: Due to its better advantages, Double-O-Tube(DOT) shield has been widely applied in shield tunnel construction. But the impact caused by shield tunnel construction on buildings hasn’t been taken seriously. Considering the interaction of building-soil-tunnel, the independent foundation frame building vertical crossed by DOT shield tunnel was simulated by 3D MIDAS/GTS software, and the impact of construction on the building was analyzed. The results show that: during the passage of the shield tunneling through the building, the settlement of the building increased. The settlement was stable and had a little rebound when shield machine already passed the building. The building’s longitudinal displacement was great larger than lateral horizontal displacement. With the increase of driving distance, the first principal stress P₁ and maximum shear strain MS_max increased and then were stable. With the increase of L, the first principal stress P₁ and maximum shear strain MS_max tended to gradually reduce the security value, and the maximum differential settlement between columns increased first and then decreased. Finally, the safety of the building was assessed comprehensively.

Abstract: Ground fissures is one of typical geo-hazards in Xi’an area, which may cause damage of various types of buildings, city lifeline projects and resources, especially endangering the construction and running of Xi’an Subway. Ground fissures in Xi’an were introduced firstly, and models of land deformations and section destroy were found around Xi’an subway. Secondly, based on the interface mechanics, mechanical characteristics of interface between stratum on fissure and metro tunnel are studied, and void underneath metro tunnel are analyzed emphatically. At last, the result of numerical simulation shows that distribution law and amount of frictional force, scale and location of void under the tunnel, influence deformation and stress of tunnel; and then it also provides a theory basis for effective forecast evolution process of void underneath.

Abstract: The polypropylene, the silica flour and the carbon fiber will be considered to be added into the concrete when test, the orthogonal theory is used in this test, 32 groups samples were made, the heater was put for heating by choosing the RABT curve, the test result was analyzed, the ratio of compressive strength loss is changed with the meter of the polypropylene textile fiber, the silica flour and the carbon fiber, there is a optimality Proportion when the ratio of compressive strength loss is low.

Abstract: In view of the easy collapse characteristic of loess highway tunnel, as well as the theory upon the reality of practical engineering. Northwestern Region Qingshui County domestic Li Jiaping loess highway tunnel construction is taken in this article. And the new questions of practical research is proposed. The technical questions during the construction of shallow loess highway tunnel, the construction plan, the distribution rule of contact stress between the support and soil, and the distortion reason of structures are all analyzed. The loess highway tunnel stability calculation and analysis is consummated. Thus the theory basis of the possible to supply the reference for this kind of project's practical application is provided.

Abstract: The support of surrounding rock under the condition of deep mining has significant challenges due to high stress and low rock strength environment. Using the method of strengthening broken rock, reinforcing support force and releasing the mine-induced stress, this study has pointed out the complementary support technology which is based on the support using bolt-wire-shotcrete and is combined with steel arched yielding support. For the purpose of permanent support, the complementary support technology could combine the each support element and adequately take advantage of load-caring capacity of surrounding rock. The monitoring data of Xiaokang coal mine, Muchengjian coal mine and Yangquhe coal mine indicate that, for the various geological conditions, complementary support system has provided powerful support force to resist large deformation of weak and broken surrounding rock. It is proved that this type of support technology could reduce the mine-induced stress as well and has economical significance.

Abstract: Several numerical models were built by FLAC3D to simulate tunnel with karst around spandrel, tunnel with karst around springe, tunnel with karst around inverted arch and tunnel with karst around side wall. The influence of karsts on the deformation of lining and the safety coefficient distribution of surrounding rock after excavation was analyzed. The results from the numerical modeling suggest as follows: karst around spandrel has extremely unfavorable effect on the deformation of lining and the safety of surrounding rock above the vault, karst around side wall also seriously affect the stability of tunnel due to the asymmetry pressure on tunnel caused by karst, consequently, auxiliary measures should be taken to handle these two cases; karst around springe and karst around inverted arch has limited adverse influence on the overall safety of tunnel, backfill measures are enough to handle these two cases.

Abstract: The uncertainty of the ground, in which a deep excavation to be conducted, is always inherent. The risk control of the excavation is therefore necessary. Based on the principle features of a deep excavation, a general process of risk control is presented in terms of design and construction, with the application of the observational method. To avoid the conflicts of the involved groups’ interests, a close co-operation between the groups in a well planned procedure is vital to the success of the risk control, especially to the case with rapid deterioration stages included.

Abstract: For the Wuyi Square Station of Changsha Subway is close to Wan Dai Hotel, the construction process is simulated by FEM software Abaqus to research the settlement and distortion of the hotel building in this paper. To simulate the soil layers and diaphragm walls, compared seepage and stress are considered in the three dimensional elastic-plasticity model, in which the building is replaced by uniform load on the ground and horizontal supports are simulated by uniform load or moving distances. The vertical displacement of building foundation has been calculated, and recharging water has been simulated outside the pit. Finally, the control standards of building settlement are proposed to control the construction security of Changsha Metro Line 2.