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Deng A.,Hohai University | Yu Y.-T.,China Jikan Geotechnical Institute | Wang H.-B.,Nanjing Forestry University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

The thermal conductivity is a critical parameter of infrastructure materials, which are used as frost-resistant fills in cold regions. The parameter is mainly determined by the material composition. A frost-resistant fill, composed of waste foundry sand (WFS), fly ash (FA), expandable polystyrene (EPS), Portland cement and water, is proposed. ISOMET apparatus is used to measure the thermal conductivity of the fills, in particular, the effect of mixing ratios on the thermal conductivity of WFS-FA-EPS fills. The test results show that the increase of EPS beads, FA or cement results in the decrease of thermal conductivity of the fills. The increase in dry density or moisture contents enhances the thermal conductivity. The components in descending order affecting the thermal conductivity are EPS, FA and water. The increase of water-EPS/FA mass ratio increases the thermal conductivity of materials. The thermal conductivity of investigated specimens ranges between 0.5~1.0 W/m K, favorably less than that of general geomaterials, e.g., 1.0~2.0 W/m K.

Ma M.,Beijing Jiaotong University | Ma M.,China Academy of Railway Sciences | Liu W.-N.,Beijing Jiaotong University | Deng G.-H.,Xian Metro Ltd. | And 2 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2013

In order to research the vibration impact on Bell Tower in Xi'an, a subway train-track-tunnel-soil 3D dynamic FE model was created. The influences of train speed on ground vibration are studied in three directions. Results show that reducing speed has obvious effects on controlling ground PPV. The model calibration method with both two positions of input and output is firstly used to study the important historic building against subway traffic-induced micro vibrations after the subway L2 opened to operate. Simulated results of both input impulse and output response match well with the measurements. The calibration model can be used to predict the vibration responses caused by the combined operation of subway L2 and L6. Three different selected routes for the proposed subway L6 are compared. When considering the micro-vibration control for Bell Tower, the route Scheme 2 and 3 are better than Scheme 1.

Ma M.,Beijing Jiaotong University | Liu W.,Beijing Jiaotong University | Qian C.,China Jikan Geotechnical Institute | Deng G.,Xian Metro Ltd | Li Y.,Xian Metro Ltd
Soil Dynamics and Earthquake Engineering | Year: 2016

There is concern regarding the long-term vibration effects caused by metro trains on historic buildings. In this paper, the impact of metro train-induced vibrations on the Bell Tower in Xi'an above two spatially overlapping tunnels was studied. Metro Line 2 has been operational since 2011, and Line 6 is still under construction. To study and control the effect of micro vibrations on the Bell Tower, a metro train-track-tunnel-soil 3D dynamic FE model was developed. The vibration response generated by Line 2 was then predicted, and the influences of train speed on ground vibration were analysed. In addition, a detailed in situ measurement, which helped calibrate the numerical model and determine the dynamic behaviour of timber structures, was performed. Finally, the calibrated models and measured results were used to predict vibrations caused by road traffic and trains from two spatially overlapping metro lines. This was performed under different route schemes and train operation conditions. The results showed that installing steel spring floating slab tracks (FST) and decreasing train speeds had obvious effects on controlling the ground peak particle velocity (PPV). Simulated results from both the input impulse and output response generated by metro Line 2 matched well with actual measurements. If correct designs are employed, it is possible to resolve the vibration problem on historic buildings caused by metro trains. © 2015 Elsevier Ltd.

Deng J.,Xi'an University of Technology | Deng J.,China Jikan Geotechnical Institute | Wang J.,Xi'an University of Technology | Men Y.,Chang'an University
Xi'an Jianzhu Keji Daxue Xuebao/Journal of Xi'an University of Architecture and Technology | Year: 2014

This paper discussed the stress characteristics and rules about anchor lattice beam based on the scientific indoor model test. This test has load on the tailing edge of the slope, get the press and strain distribution of the bottom soil of the lattice beam by the pressure cell and strain gauge put on the lattice beam. The result shows that with the increase of load pressure, the press and strain on the lattice beam increases, but the press on the cantilever end and mid-span of the lattice beam became diminished and the strain increased. On the other hand, the press on the cross of the lattice beam became greater and the strain became diminished. Overall the press and strain distribution on the lattice beam oresent to be of a triangle type.

Gao G.Y.,Tongji University | Li N.,Tongji University | Zheng J.G.,China Jikan Geotechnical Institute
Applied Mechanics and Materials | Year: 2010

In this paper, an exploration was presented to access the actual screening effectiveness of concrete wave impeding block (WIB) and the influence of WIB embedded depth on the vertical vibration isolation effect under the continuous vertical loading. Furthermore, the displacements of measuring points were simulated with a semi-analytical boundary element method (BEM) and validated by the measured records. It was found that a concrete WIB with a reasonable embedded depth was able to decrease the ground vibration greatly. It was also proved that decreasing the embedded depth was an efficient measure for WIB to reduce the dynamic response of ground. Besides, the good qualitative agreement between the calculation and the experiment proved the reliability of the numerical method. © (2010) Trans Tech Publications, Switzerland.

Liu Z.-H.,China Jikan Geotechnical Institute | Zheng J.-G.,China Jikan Geotechnical Institute | Yu Y.-T.,China Jikan Geotechnical Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

A technology for stress tests on PHC tubular piles is developed, and is applied in vertical static loading tests on PHC piles in collapsible loess. Based on the tests, bearing capacity and skin friction distribution rules of PHC piles in collapsible loess with natural and soaked soil conditions are studied. The test results show that if PHC piles consist of several segments, the skin friction of the upper part of the piles may be lower when the soil around the piles is dry loess, in this case, the skin friction cannot be effectively raised after the soil is soaked, and the negative skin friction is also lower when the self-weight collapse settlement around the piles occurred. The skin friction of lower part at different depths shows a single-peak curve, and the peak depth gradually moves down with the increase of load. Under the ultimate load, compression of PHC pile body dominates total settlement when the soil around the piles is interbedded between loess and paleosol.

Tang H.,China Jikan Geotechnical Institute | Liu D.-J.,Hefei University of Technology
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

A dynamic model of vibration-sourced prompting and its corresponding governing equation are quoted. By solving the equations by four-step Runge-Kutta. With the general parameters of the vibration sources and pile, a figure of the pulse of exciting force is obtained. Then the figure is compared with another two different figures corresponding to two functions of pulse simulation .As a result, the accuracy and applicability of the functions is estimated. The effect of the mass of the vibration source, impact speed and the softness or hardness degree of the material on the strength and width of exciting force is simulated by changing a single parameter. Finally, it is demonstrated that the results from this solution are in accordance with the field test. Meanwhile the advantages and disadvantages of the model are also analyzed.

Qian C.Y.,China Jikan Geotechnical Institute | Zheng J.-G.,China Jikan Geotechnical Institute | Su L.-J.,Xi'an University of Architecture and Technology
14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering | Year: 2011

The structural characteristics of the Xi'an ancient city wall and the existing threats to its safety were briefly introduced. The theory background of ground penetrating radar (GPR) and methods for interpreting GPR images were presented and explained. A detailed investigation of a section of the city wall was conducted using GPR. The typical internal faults of the city wall was revealed by GPR images and further approved by actual data, which provided detailed information for the safety assessment and regular maintenance of the city wall. The GPR technique is non-destructive, effective and accurate and should be further investigated and applied in future applications in inspection of ancient structures.

Zheng J.-G.,China Jikan Geotechnical Institute | Wang T.,China Jikan Geotechnical Institute | Zhang J.-W.,China Jikan Geotechnical Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

The advantages and disadvantages of some commonly used settlement prediction models are analyzed. comparatively An optimal method of settlement prediction by fitting precision and prediction accuracy is proposed. A better loess subgrade settlement prediction method is put forward based on the measured data of Zhengzhou-Xi'an passenger dedicated line. The fitting precision and the prediction accuracy of combination forecasting model are studied. It is concluded that the fitting precision and the prediction accuracy of combination forecasting model should be higher then any other prediction methods because of its comprehensive nature. But the members of combination forecasting model must be selected before prediction. Prediction accuracy and screening criteria are closely linked. How to choose better screening criteria which make square sum of error small in the prerequisite conditions of weight coefficient being greater than zero still need further study.

Liu F.,Xi'an University of Architecture and Technology | Zheng J.-G.,China Jikan Geotechnical Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

The static load tests are adopted to investigate 2 PHC tubular piles in collapsible loess site under natural, pre-soaked and post-soaked soil conditions. Based on the additional settlement of piles during water immersion and stress tests in the process of static load tests, the bearing capacity behavior, axial force and lateral friction are analyzed. The test results show that there is no occurrence of negative skin friction under water immersion condition, and the additional settlement of the piles does not result from negative skin friction triggered by the self-weight collapse settlement. The transfer of axial force is slow from ground to the depth of 6 m, which behaves vertical line, and is nonlinear at the lower part of the piles. The curves of lateral friction varying with depth have different anti bending points. The difference between the upper part and lower part of the piles at anti bending points is clear. Local envelope zone appears under the ultimate load.

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