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Xu H.,Wuhan University | Liu J.,Wuhan University | Fan C.,Anhui Expressway Holding Corporation | Cao J.,Anhui Expressway Holding Corporation
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2013

Two-dimensional forward modeling was taken through the finite-difference time domain method for the wave field characteristics of several kinds of diseases in tunnel lining, including disengaging, segregation, reinforced deletion, disengaging and segregation under reinforcements. Then the simulation and practical works were compared and analyzed. The results show that forward modeling of the common tunnel lining diseases can effectively provide evidence for interpretation of radar data; the thickness of disengaging can be accurately calculated as long as this thickness is greater than one quarter of the wavelength with which electromagnetic waves propagate in the air; these common diseases from the radar section can be resolved by the radar wave field characteristics of disengaging, segregation and reinforcement; when disengaging and segregation appear under reinforcements, the disengaging under reinforcements can be recognized clearly from the change of energy and phase in radar sections as well as the change of energy in the multi-channel spectra.

Liu T.,Anhui Expressway Holding Corporation | Cao X.,Anhui Expressway Holding Corporation | Li X.,Tongji University
Modern Tunnelling Technology | Year: 2015

Considering that improper treatment of water inflow during tunnel construction may seriously affect local ecological and social environments, and using a typical water-inflow section of the Mingtangshan tunnel as an example, this paper proposes a conceptual hydrogeological model for water inflow in a fractured zone based on a small-scale test for hydraulic pressure at a water-stopping point on a typical section. It presents three fissure water-distribution models for the fractured zone before and after excavation. The results show that: 1) a perched water saturated zone in the surface weathered fissure rock layer will appear or disappear after water inflows with the coming of the wet season or dry season; 2) the hydraulic pressure of the water-inflow point increases rapidly after water stopping and then slows down, which can be reflected by a logarithmic model; 3) a water-head depression cone is formed near a single water inflow point, and a balance will be reached by connecting to other interlinked points of water inflow after water stopping; and 4) seven-day monitoring indicates that a stable hydraulic pressure can be achieved after 24 hours of water stopping. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Zhou C.,Wuhan University | Liu J.-P.,Wuhan University | Zeng X.-Z.,Wuhan University | Fan C.-Y.,Anhui Expressway Holding Corporation | Cao J.,Anhui Expressway Holding Corporation
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

The dispersion information of Rayleigh wave can be used to calculate shallow S-wave velocity structure effectively. But in the large time-space sampling seismic data, the high-frequency signal components are usually aliased seriously, or even exceeding the cycle of the wave because of the low velocity of Rayleigh wave. This can decrease the SNR (signal-noise ratio) in frequency-velocity domain, and affect the accuracy of dispersion curves, especially in the high-frequency section. The interpolation of Rayleigh waves was accomplished based on wavelet transform (WT). According to the characteristic of linear seismic event, linear normal moveout (LNMO) was introduced into the process of the interpolation which could improve the interpolation effects of the high-frequency components. This method was used to calculate both synthetic and real data examples, extracted the frequency-velocity spectrums, and analyzed their frequency-velocity spectrums before and after interpolation. The results show that the interpolation method is correct, and it can improve the SNR in frequency-velocity domain and the accuracy of the dispersion curves. All these provide theoretical principle for extracting dispersion curves of the Rayleigh wave in the large time-space sampling seismic data.

Gong W.,Nanjing Southeast University | Wang L.,Nanjing Southeast University | Yin Y.,Anhui Expressway Holding Corporation
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2015

According to the situation of the shortage of the bearing capacity of the soft and thick covering stratum, the root- caisson foundation, a new type of caisson foundation with variable cross-section, was introduced. The self-balanced test method was utilized in the field tests to investigate the vertical bearing behavior of a root-caisson foundation and a traditional one. The mechanism of vertical bearing capacity root-caisson foundation was analyzed, and the improvements of bearing capacity due to the soil compaction and the bending resistance of roots were discussed. The results indicate that the rootstalks are capable of activating a large range of soil to bear the load, and with reasonable installation of rootstalks, the ultimate bearing capacity of a root foundation is greatly larger than that of a traditional caisson foundation. Compared with the traditional caissons, the vertical bearing capacity of root-caisson foundations could be increased roughly by 100% and 63% in different bearing layer. Root foundation owned the good adaptability in thick covering stratum region. At the early stage of loading, the root foundation then had showed that it owned the ability to enhance the vertical bearing capacity and the enhancement effect was more obvious with the loading increasing. Root foundation could be considered to replace the traditional open caisson foundation or friction pile foundation in the thick covering stratum region. ©, 2015, Editorial Office of China Civil Engineering Journal. All right reserved.

Mu L.-L.,Tongji University | Huang M.-S.,Tongji University | Gong W.-M.,Nanjing Southeast University | Yin Y.-G.,Anhui Expressway Holding Corporation
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

Anchorage foundation is a new structural foundation which can effectively improve its bearing capacity by increasing a small amount of material that due to the designability of itself. It is necessary to analyze the mechanical behavior of anchorage foundation due to the shortage of corresponding theoretical research. In-situ tests of an anchorage foundation of Huaihe Super Bridge are simulated by elastoplastic finite element method to demonstrate the effectiveness of numerical simulations and suitable selection of material parameters. The mechanical behaviour of anchorage foundations is then further studied by comparing that of a caisson without anchors. Meanwhile, the distribution of moment on anchor is analyzed; and the influence of anchors' embedded depth on the bearing capacity is studied. The results show that the lateral bearing capacity of anchorage foundations can be effectively improved by a proper setting of anchors.

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