Advanced Materials Research Vols. 250-253

Abstract: Under the repeated blasting vibrations, the roof of the mined-out areas will suddenly collapse and fall because of its accumulated damage, which is a hidden danger for the miners and equipment on the surface. Based on the mined-out areas in Antaibao Surface Mine, the three-dimension engineering geological model and computational model were built using FLAC^3D technique. According to the effect of the load of the mechanical construction equipment, and the blasting vibration velocity recorded by field monitoring, the equal-time-interval blasting vibration as normal incidence was exerted on the surface of the mined-out areas three times. Consequently the accumulated damage effect of the roof and surrounding rocks of mined-out areas were analyzed, the stress concentration extent and the range of principal stress were discussed as well. The dynamic response characteristics of deformation and the accumulated progressive displacement were revealed via the monitoring displacement curves. The above mentioned results can provide theoretical and technical basis for similar projects on reducing the hidden danger and ensuring safe mining.

Abstract: The computation method of retaining wall reliability indexes is intruduced, and the analysis model of gravity retaining wall reliability is established in this paper. And the reliability of gravity retaining wall reliability is analyzeda using the center collocation method of second order moment. Based on the comparison of the calculation result of safety coefficient method and that of reliability analysis method, the safety factor method can't correctly reflect the reliability of gravity retaining wall, but the center collocation method of second order moment can correctly reflect the reliability of gravity retaining wall.

Abstract: With China's steel structure housing industry vigorously develop, the steel structure housing has been widely used in our country. In this paper, the steel structure housing structure and design essentials are introduced. Among design essentials, steel, the choice of connecting materials and wall materials, node design, the waterproof design of toilet and kitchen, floor systems design, the corrosion of steel structure, steel welding design and so on are mainly introduced.

Abstract: The time domain responses of the immersed tunnel element under typical load combination case during its immersion are investigated based on the 3D potential method. The varied cross-section complicated model is built. The typical environmental and immersion parameters are considered. The results of different line models are compared and investigated. Numerical results demonstrate the effects of the mooring lines’ condition. The “optimum” balance between relative large mooring stiffness and relative safety tension can be realized by combining the coarse calculation and hydraulic exact analysis.

Abstract: Based on the practice of Huolang-yu tunnel of Mixing road reconstruction, this paper studies the monitoring of ground surface vibration and the technology of controlled blasting. The results show: (1) the ground surface vibration declines from constructed position to non-excavated areas along tunnel excavation direction. (2) The vibration control of wedge cutting holes blasting is the key to reduce or eliminate shallow tunnel vibrating calamity. And the replacement of the multi-stage small wedge cutting holes to the big wedge cutting holes ameliorates blasting vibration and rock fragmentation. (3) The overall monitoring of shallow tunnel blasting vibration and the effects, and optimum of the blasting design not only reduce blasting vibration but also ensure large circulation footage.

Abstract: Four constructional columns with concrete porous brick walls were constructed for low cyclic loading test. The damage on the characteristics and strength of the wall, hysteresis curve, ductility and other seismic performance were analyzed. Setting constructional columns in the wall at both ends increase the ultimate strength and improve its deformation, ductility and other properties. Meanwhile the height-wide-ratio of wall, axial pressure and other factors on the shear bearing capacity on the wall have been studied. Based on the shear capacity formula of wall in the Structural Seismic Design Code, considering the contribution of the constructional columns on the shear strength, according to the results, the shear capacity formula of constructional columns with concrete brick walls is presented.

Abstract: Prestressed concrete double Tee floor slabs are widely used for the roof of building construction. Some problems are met during the development practice of this type of precast structures. Firstly, the overhang flange of the traditional double Tee floor slab is not enough large in the view of economic and utilization. Secondly, it is not easy to dispose the skylights on the roof used double Tee floor slabs in the workshops or the gymnasiums. Thirdly, most of the beams are produced in prestressing plants, but very few productions are made in site. Therefore, a new type of prestressed concrete double Tee floor slabs have been designed with some characters such as 3.0-m outside flange, flange slabs with rectangular opening holes for the skylights or not, and the beams produced in the prestressing plants with pre-tensioning prestressing tendons or post-tensioning with the strands in site.

Abstract: Based on the characteristics of blasting vibration wave and the design response spectrum, this paper puts forward an analytical method on dynamic response of building structure in blasting vibration. Example analysis shows that this analysis method is more reliable and scientific compared with the analytical method which takes the single physical vibration parameter as the criterion to assess the damage in blasting vibration; the blasting vibration load is determined by the first vibration mode, and the influence of higer level vibration mode can be ignored. The interlaminar shearing force distribution carries the feature that the shearing force on the top of the building structure is smaller than that on the bottom. Therefore, in blasting vibration, the bottom of a building structure is easier to be damaged.

Abstract: The stiffness and shear strength of soft clay attenuate under long-term cyclic loading, resulting in reduced foundation bearing capacity of road. The variation regularity of undrained shear strength of saturated soft clay which is normally consolidated or over consolidated under cyclic loading was studied with two-way vibration triaxial test, and some useful results are obtained.

Abstract: With the development of the steel-concrete composite structure, it has been found the new application form: steel-concrete composite bridge tower. Compared with the traditional concrete filled steel tubular column, composite bridge tower has connectors between steel panels and core concrete. Therefore, the mechanical characteristics of the composite tower are somewhat different with that of the composite column with no connectors. Some researches have been done on the composite tower and relevant research progress is introduced in this paper, which including the researches on composite bridge towers with different cross section types and with different connector types between steel panels and concrete.