Applied Mechanics and Materials Vols. 353-356

Abstract: With the background of Qingdao Baoer~Hexi subway station in Water-rich Sand Stratum, research the application of horizontal jet grouting in soils underlain by rock. Introduce the difficulties in engineering and the optimization process in horizontal jet grouting. In order to understand its reinforcement effect, samples to test the point of load and compressive strength, at the same time, analyzes the impact of stratum settlement based on the monitoring data. Monitoring results show that horizontal jet grouting has great effects in control the settlement. The research results would provide guidance for the subsequent construction.

Abstract: Based on the fluid-structure interaction theory, FLAC3D was adopted to conduct a numerical simulation on the excavation of hong shigou hard rock tunnel. The basic mechanical properties for rock mass changed significantly during the process of secondary stress adjustments, and the rock deterioration constitutive model (RDM) can accurately reflect both the abruptness of the rock yield failure and the changes of mechanical parameters after yield. On the basis of RDM, the permeability coefficient with equivalent plastic strain function was introduced which can update the permeability coefficient. The results showed that both the surrounding rock displacement and the volume of plastic zone increased significantly because of the seepage action. Therefore, the seepage of fissure water on the hard rock should be fully considered during excavating and supporting in order to prevent accidents such as water inrush and sudden collapse.

Abstract: The deformation monitoring of surrounding rock and data processing in tunnel is the foundation and safety technical support of underground engineering information control and management. However, due to the special environment in the underground engineering construction, acquiring the deformation information of surrounding rock accurately and fast to assess the stability of surrounding rock is becoming one of the bottleneck problems for underground construction project information to be solved. According to the underground engineering projects, Based on the dynamic monitoring data processing and analysis, a set of underground engineering construction monitoring measurement data processing system is established, which can meet the acquisition of the monitoring measurement data, the arrangement of the measured data, data analysis and feedback, the monitoring data regression analysis.

Abstract: Inner Mongolia's xilingol league area of chagannaoers main inclined shaft is extremely soft rock roadway with the properties of 0.12 ~ 5.12MPa in uniaxial compressive strength of rock, 60.6% in clay mineral content and 82% of clay mineral composition is montmorillonite, and with the feature of argillation and expansion by absorbing water in surrounding rock. The two previous supporting schemes for this roadway were double16a I-beam and 650mm concrete layer as the first scheme, and close U36 steel stents as the repairing scheme, respectively. Both of them were failed to control deformation failure of surrounding rock. In this paper, a new supporting scheme was proposed by testing mechanics parameters and mineral composition of surrounding rock, analyzing hydraulic properties of surrounding rock and deformation failure, and evaluating surrounding rock load. This new scheme consists of high strength pressure-bearing ring supporting technology based on concrete filled steel tubular support and surrounding rock partial pressure-releasing technology. Aiming at deformation of side walls of the main inclined shaft roadway, a test was carried out to study the bending resistance of the support and improve the support. The industrial test showed that the new supporting scheme can effectively control the deformation of the main inclined shaft surrounding rock and realize long-term stability of roadway.

Abstract: Water inflow was the main damage during blasting excavation of subsea tunnel, disturbance due to blasting could also induce water inflow. Based on the blasting mechanism of water-bearing fractured rock-mass, stress state and breaking-down process of the fracture was analyzed, which was affected by dynamic stress field (blasting effect) and static stress field (water and in-situ stress). With the affect of overlapping dynamic and static stress field, the calculation formula of the critical inner water pressure in water inflow was presented. At last, using these formulas, critic water press and radial extent were calculated of water-bearing fractured rock-mass in Xiamen subsea tunnel.

Abstract: Xiaohegou tunnel is an under construction shallow expansive loess tunnel with Large Pipe Roof Support. Large Pipe Roof Support construction and excavation of the tunnel was simulated by the Fast Lagrangian finite difference software Flac3D. The pipe roof loading states and the deformation of surrounding rock in front of the tunnel face was obtained in each step of excavation, and the results was compared with a simulation without Large Pipe Roof Support. The results show that the reinforcement effect of Pipe Roof was to restrain the plastic flow of soft soil, and Pipe Roof help to share soil pressure, which could decrease the tunnel deformation effectively.

Abstract: A study on C80 high performance concrete used in deep freezing mine shaft liner is made. Test results are listed as follows: (1) Concretes compressive strength at 1 day is 53.0 MPa, while the compressive strength at 28 days is 93.5 MPa. (2) The diffusion coefficient of chloride ion at 28 days is 9.8×10^-14m²/s, and freezing-thawing cycle is over 1000 times. The evidence above proves that this concrete can satisfy the requirements of C80 high performance concrete used in freezing shaft sinking techniques.

Abstract: Based on rock burst mechanism and the present research situation of control technique, pressure relief process of drilling to rock burst roadway is modeled by numerical simulation software, the contrast and analysis of stress field of surrounding rock are put up with and without pressure relief. The results of the calculation indicate that after drilling high stress area on the both sides of the roadway reduces obviously, but stress peak increases and its position is not converted into the deep areas evidently. It is the energy of the high stress area that makes the rock mass between the drillings failure, which achieves the purpose of pressure relief. Drilling diameter and space between drillings are main factors influencing pressure relief effect. The major the drilling diameter and the smaller the space between boreholes, the more complete the rock mass between the drillings failure and the better the pressure relief effect.

Abstract: This study developed a safety evaluation model for traffic operation environment of freeway tunnel based on the grey entropy weight clustering. Firstly, a safety evaluation system was proposed including four aspects related road conditions, traffic operating conditions, environmental conditions and climate condition. Secondly, whitenization weight function was defined and weights of indexes were determined by entropy theory. Thirdly, the grey entropy clustering coefficient was calculated, and the safety level for traffic operation environment of freeway tunnels was evaluated. Finally, a case study of seven tunnels of XI-HAN freeway was conducted to verify the feasibility and effectiveness of the model.

Abstract: In this paper, through theoretical analysis and finite element of numerical calculation method, superimposed influence effect in the process of typical complex foundation pit group excavation was analysis and research. Put forward hazard prevention methods aim at the superposition effect in the process of construction, at the same time, the information construction means monitoring is conducted to be verified. Results show that, the relevant control measures was effectively control the displacement of deep foundation pit and surrounding environment.