Advanced Materials Research Vols. 368-373

Abstract: Taken extremely complex and specific underground chamber excavation of TBM assembly in Jinping Ⅱ Hydropower Station as the background, the research was done on construction blasting vibration effects and control technology in the large cavern under high crustal stress. Combined theoretical analysis with field trials and other methods, chamber controlled blasting program and its parameters of better control of blasting vibrations were set in regard with the geological conditions of TBM assembly chamber, cross-section shape and size, chamber body structure and sequence of construction methods. The blasting vibration test program under complex conditions and measuring points were arranged appropriately. The result is that the blasting vibration attenuation coefficient values and was 1.24 and 0.56. Practice shows that the impact of blasting vibration on rock and underground structures is lesser, therefore the chamber driving speed and construction safety can be ensured by the chamber controlled blasting technology for construction. The blasting vibration attenuation that is deduced from the practice can better reflect the effect of blasting vibration chamber: according to the correlation between dose and level distance of blasting, safe construction blasting can be guided. In addition, there is a greater relevance between blasting vibration control method, materials and strength of underground structures. As blasting dose is the same, with increased age and strength of concrete, its ability to withstand the intensity of blasting vibration is also increased dramatically.

Abstract: Based on shaking table model test, each response of the pipe models is obtained by inputting different types, amplitudes, frequencies of seismic waves and white noise excitation. The transfer function of the measuring point related to the vibration table, natural frequency of soil and pile, power spectrum and other parameters are obtained by Matlab programming model. By applicating SeismoSignal the propagation of seismic waves in the soil was gotten. Reveal the regulation of the propagation of the seismic waves in the pile-soil system. Investigate dynamic characteristics and dynamic response of the pile and soil in the earthquake and the transfer laws of the seismic wave energy. Provide a useful reference for the pile foundation seismic design.

Abstract: Lin'an City, a building located in the downtown, surrounding and supermarkets, banks, residential quarters, office space and many other enterprises and adjacent companys.Complex building is difficult to remove. The direction of the main building collapsed requires accurately, to ensure blasting construction safety and the safety of the adjacent environment. To this end, on the basis of the removal program design,construction specific issues that need attention and contingency plans were discussed. Such blasting and demolition projects control points and the problem should pay attention to are summarized.

Abstract: The underground cavities of the Guandi Hydropower Station comprise four pressure division tunnels, a generator chamber, a main transformer chamber, a tail water control chamber and two tail water tunnels and arrange in the basalt mountain on the right bank of the dam. Based on the brief introduction of cavity arrangement, geological conditions, monitoring design and execution, the deformation magnitude and deformation characteristics of the three major cavities are focused on analyzing. The stability of the cavities is evaluated. The quality of the surrounding rock masses of the underground cavities of the Guandi Hydropower Station is good and the deformation is normally less than 30mm. However, some parts have large deformation due to the influence of the structure surfaces and the maximum deformation is 61.49 mm. Most of the parts with larger deformation are the middle and upper positions of the side walls and rock anchor beam positions. The structure surfaces have noticeable action for controlling the surrounding rock mass deformation. The stability of the cavities is good.

Abstract: By means of pseudo-dynamic theory, a new calculating method is presented to calculate the pseudo-dynamic seismic active earth pressure behind rigid retaining wall. Considering time and phase difference within the backfills, the horizontal slices is used to analyze the distribution of seismic active force behind retaining wall in more realistic manner. Under the assumption that the soil backfills are rigid body, the equations derived in this paper can be degenerated to Mononobe-Okabe equations. Through numerical analysis, it is shown that the values of seismic active force obtained from present study are smaller than those obtained from Mononobe-Okabe theory and the distribution of seismic force along the depth of the wall is nonlinear. It is also found that the action point of the total seismic active earth pressure is higher than one third of the wall height, which is corresponding to previous experimental results.

Abstract: Based on virtual soil pile model, the influence of sediment properties on complex impedance at the head of rock-socketed pile is theoretically investigated by virtue of Laplace transform technique and impedance function transfer method. Firstly, the sediment under pile toe is assumed to be virtual soil pile which the cross-section area is the same as the pile. The layered soils surrounding pile are described with plane strain model. Then, by means of initial conditions and boundary conditions of the soil-pile system, the complex impedance at rock-socketed pile head in frequency domain is derived at condition of arbitrary excitation on the pile head. At last, by using parametric study method, the influence of sediment properties on complex impedance at rock-socketed pile head is studied. It is shown that sediment properties have significant influence on complex impedance at the head of rock-socketed pile.

Abstract: By using the numerical analysis method as the test means, this paper simulated and studied the main factors of ground loss which was caused by the full face excavation of shallow tunnels. The results of the numerical experimentation make clear that: in the same conditions, the inverted arch reinforcement is more effective than the vault reinforcement, the advanced reinforcement of inverted arch is more effective than Radial reinforcement of that, and the vault reinforcement doesn’t work or the effect isn’t obvious.

Abstract: This article used the elastic-plastic finite element analysis method based on strength reduction theory and researched the regularity of longitudinal formation cracks during the loess tunnel construction. It analyzed the development trend of the crack dips and the distance between the surface crack and the tunnel center by different depth conditions when using the full section method and the bench cut method during the construction. From that it can get the boundary value of tunnel depth that the longitudinal crack can reach the ground. The result shows that: (1) Through the finite element analysis of the continuum structural model, it is feasible and effective to use the method, which is based on the area including the shear stress greater than the cohesive stress, the mutant horizontal displacement, and the change trend of the vertical displacement, to analyze the trend and the scope of longitudinal cracks after the excavation of the loess tunnels. (2) When using the full section method, the longitudinal cracks can reach the ground as long as the buried depth is less than 50m.With the increase of the buried depth, both of the depth of the cracks and the distance between the cracks and the tunnel center are all increased and the crack dips are changeable whose range is 56º~67º. However when the buried depth is more than 50m, the cracks can’t reach the ground and develop from the vault to the ground. The slip tendency near the ground is diminished. With the increase of the buried depth, the dips get larger, but the distance between the cracks and the tunnel center and the crack depth are invariable. (3) When using the-bench-cut method, the development trend of the formation crack is similar to that of the full section method. The cracks can reach the ground when the depth is less than 40m, and the range of the cracks is 56º~62º, or else the cracks can’t reach the ground. (4) From controlling the surface cracks, the bench cut method is superior to the full section method.

Abstract: Subway construction involves a large number of excavation engineering. For the restrictions caused by conditions on the spot,Many foundation pits projects showed some features of clear spatial effects, complex stress characteristics,multiplex affecting factors, it often can not be suit for the applicable conditions of the existed earth pressure theory very well. On the background of BeiLing Station Passageway construction in Shenyang Subway Line No.2, Through counting and analyzing the results of three-dimensional numerical simulation in detail,summing up regulations of Taishan bridge abutment displacement in the horizontal plane. Force act on 4,5foundations fender post present trapezium and parabola distribution with depth respectively. So it is concluded the properties of foundation pit earth pressure, proposing a simple calculating model comparing its results with numerical simulation results to verify the reasonableness of the model. So the problem which is how to calculate the earth pressure under the complexity of obvious spatial effects and a variety of environmental conditions can be solved and reference experiences on the calculation of earth pressure can be provided to similar Follow-up projects

Abstract: The soil-water characteristic curve is an important constitutive feature of unsaturated soils, defining the relationship between the soil suction and moisture content. Mineral component and pore space topology are the most important physical factors affecting the soil-water characteristic, and that dry density synthetically reflects the mineral component and pore space topology. Compaction is a classical application involving unsaturated soil, and dry density represents the pore structure at special moisture content. Soil water characteristic curve for compacted loess is studied by test, and the effect of dry density on soil water characteristic curve is discussed. Based the soil-water characteristic curve and compaction curve, mechanism of compaction is explained. Research results show that the soil-water characteristic curves for all dry density soil intersect at the point, which is optimize moisture content, and suction is the most important factor affecting the compaction.