Advanced Materials Research Vols. 168-170

Abstract: Lateral variations of the karst of deep buried tunnel engineering is big. The heterogeneity of it is strong. The tunnel is combined with Changsha Rail Transit Line 2 at one section of the first phase construction. Under the urban environmental conditions, it is considered to use auxiliary seismic wave imaging method assistanting with Rayleigh surface wave method. It is the detection and prediction method of comprehensive geological analysis of karst hazard, which identified the underground targets of deep buried tunnel effectively. To avoid a single technique multiple solutions, it can reflect the complexity of karst formations geological features objectively. Therefore, it can reduce the risk of drilling and take appropriate treatment measures to provide adequate and reliable basis.

Abstract: Rapid urbanization process brings large-scale excavation engineering and subway tunnel in city. Especially ,some excavations are just above the subway tunnel with almost no distance between the excavations and the subway. How to effectively reduce the deformation of tunnel becomes a subject worthy of researching. Based on the underground space in Zhujiang New Town which would be constructed cross metro tunnel, protecting technology has been proposed to guarantee the metro tunnel’s safety by application of time and space effect, which could benefit the following similar projects.

Abstract: Chengmenshan open pit has been constructed to be the biggest copper pit in China. The slope designed with empirical rock mass rating and engineering analogy needs reinvestigation and evaluation for its overall stability. With help of SURPAC, the topographic contour of the mine was converted into surface model. Then the geological information of the mine was embedded into the numerical solid model by NURBS treatment of the core loggings. Through overall stability analysis with MIDAS, it was found that there was no obvious failure in the pit with the current design. But the major principal stress at the north especially the north-east corner of the pit tended to be high, so the width of the bench below the high stress region is suggested to be widened for possible collapse in this region. And field observation should be carried out in the region. Once evident slip or collapse happens, anchor and netting structures should be used. At the same time, high shear stress zones were revealed at the south-east of the outside limit of the pit. More planting is suggested to avoid soil creep or even landslides in heavy rain.

Abstract: Approximately 2 μm thick CrN and CrAlN coatings were synthesized on silicon and spring steel substrate by multi-arc ion plating technology. The nanoindentation techniques, Auger electron spectroscopy (AES) analysis, scanning electron microscopy, X-ray diffraction and oxidation furnace were used to investigate the mechanical property, oxidation resistance and microstructure of the coatings. The XRD data showed that the CrN and CrAlN coatings exhibited B1 NaCl structure. Nanoindentation measurements showed that as-deposited CrN and CrAlN coatings exhibited a hardness of 19 and 30 GPa respectively. Compared with CrN coatings, the CrAlN composite coatings show much better oxidation resistance. And the oxidation resistance ability will enhance with increasing Al content, because A12O3 will form after oxidation in high temperature condition which could reduce the diffusivity ability of oxygen.

Abstract: This paper presented a new mild steel slit damper(SSD). The new shape was parabolic according to all the cross section having the same maximal stress, and the elastic stiffness and yield displacement formula were derived. Finite element analysis showed that the parabolic shaped damper had a more reasonable load - displacement curve compared with the previously proposed shape. The theoretical stiffness and yield displacement were consistent with the results by finite element method (FEM), and that indicated the presented design method was simple and feasible.

Abstract: On the stability analysis of complex slope, the determination of rock-soil masses shear strength parameters is very important. It’s very necessary to use the back analysis method to verify experiment result of rock-soil masses parameters for the important slope engineering. Because the sensitivity of shear strength parameters to displacement parameters is very poor, so that we couldn’t get the satisfactory shear strength parameters result by traditional back analysis method. Aiming at the problems of traditional back analysis method, this paper puts forward a totally new method of back analysis, which is applicable to the shear strength parameters of rock-soil masses through the integration of complex variable differentiation method, optimization method and elastic-plasticity finite-element method. The method mathematically back calculates shear strength parameters of rock-soil masses on the basis of displacement of measuring point. The sample calculation result indicates that the method possesses high accuracy and searching efficiency, and is a method of back analysis of displacement deserving popularizing.

Abstract: Freeze-thaw action is one of causes to loess disaster. Loess structure and mechanical properties are quite different due to its structural model, unsaturation and salt content, which make loess freezing much complex. The samples from the site are set with different moisture content and lowered their temperature to 0°C, -10°C and -20°C respectively, and then the microscopic damage propagation and damage structural variation in the internal loess have been studied under the different freezing temperatures through CT scanning experimental technique. With zoning methods and zoning statistic frequency, the process of damage evolution has been analyzed, which provides specific guideline for researches on geotechnical engineering in loess region.

Abstract: Taking axisymmetric wave effect of soil into account, longitudinal vibration of pile in viscous damping layered soils undergoing arbitrary load is theoretically investigated. An analytical solution for admittance at the level of the pile head in frequency domain is yielded. So is a semi-analytical solution for velocity response in time-domain subjected to a semi-sine exciting force. Based on the solutions proposed herein, the effects of variety of soil modulus on admittance curves and reflection wave curves are emphatically discussed. The conclusions can provide theoretical guidance for non-destruction test of piles.

Abstract: the aging existing in use and construction of bituminous pavement will directly resulting in shortening of the pavement’s service life. It is provide the theoretical basis of the design and construction of the SBS modified asphalt mixture to analyze the influence of aging to the rheological property of SBS modified asphalt under high temperature. The testing for the rheological property of three kinds SBS modified asphalt under high temperature has been finished before and after the aging in construction by Brookfield DV Ⅱ+ type of rotation viscometer. The results indicated that viscosity will be increased and the sensitivity of SBS modified asphalt to viscosity will also be lowered along with increase of aging degree. The testing for the rheological property of three kinds of SBS modified asphalt has been finished before and after aging in usage period by the dynamic shear rheometer (DSR). The results shown that G* will be continually increased along with increase of aging degree and this is consistent with change of base asphalt. And this shown that the increase of G* can only come down to oxidation and aging of base asphalt contained in the modified asphalt and also, asphaltene in SBS modified asphalt will be changing in the mode same with that of base asphalt.

Abstract: The distributions of stress intensity factor KI and KII in notched beam specimens have been obtained in this paper by researching on internal force distributions, photoelastic experiments and statistics from numerical results. Two approximate formulae of KI and KII have been constructed. A simple and correct way to calculate KI and KII of beam is provided.