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Qiu K.,Nanjing Southeast University | Chen H.,Nanjing Southeast University | Sun W.,Nanjing Southeast University | Sun L.,Nanjing Southeast University | And 2 more authors.
Journal of Materials in Civil Engineering | Year: 2014

To determine the mechanical properties of cement asphalt mortar (CAM) in the field, this contribution first presents a model to elaborate the relationship of strength to ultrasonic pulse velocity (UPV). Next, a mechanical test (compressive, flexural strength, and static modulus) and a UPV test are conducted on CAM at different ages to calibrate the proposed model. Finally, three fitted formulas are established based on the proposed model and verified with additional test results. Results suggest that a UPV test is a helpful method for estimating the mechanical properties of CAM in the field and can reach a high precision. © 2014 American Society of Civil Engineers.


Liu J.,Southwest Jiaotong University | Zhao J.,Southwest Jiaotong University | Zhao G.,Southwest Jiaotong University | Zhao G.,Beijing Shanghai High Speed Railway Ltd Company | And 2 more authors.
Zhongguo Tiedao Kexue/China Railway Science | Year: 2011

Combining with the field test of CFG pile-net composite foundation, the additional soil stress of upper soil between piles was analyzed. The test shows that the soil stress of upper soil is just increased in a certain range of depth, while the additional soil stress decreases quickly with depth and the axial force of upper pile increases with depth. Using axially symmetric cylindrical coordinate, for rigid-pile composite foundation without pile cap, the pile-soil interaction in the treatment area of single pile is analyzed, and a calculation method of additional stress in the upper soil of pile-net composite foundation is created. The results show that, under the action of the shearing force in the soil and friction among pile and soil, the load supported by pile and soil is redistributed. The load supported by soil is decreased and the load supported by pile is increased. The larger the cohesion and friction angle of soil is, the faster the decay rate of the additional stress of soil will be. By comparing the calculation value with the result of numerical simulation and field test, it shows that the calculation method proposed in this paper is reliable.


Zou L.,Southwest Jiaotong University | Wu X.,Southwest Jiaotong University | Ma J.,Southwest Jiaotong University | Peng S.,Beijing Shanghai High speed Railway Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

Beijing-Shanghai high-speed railway field tests on post grouting of pile group foundation have been carried out. By analyzing the long-term settlement measured data of post grouting and non-grouting pile group foundation, the settlement development laws of post grouting and non-grouting long pile group foundation in deep soft soil have been researched. The stable time of settlement of pile group foundation are analyzed, and the influence mechanism of the post grouting effect on pile group settlement and its development laws are discussed. The conclusions are that both pile shaft grouting and pile end grouting have obvious function on the control of the settlement of long pile group foundation in deep soft soil; and the control effect of pile end grouting is superior to pile shaft grouting. For shortening time of consolidation settlement, the effect of pile end grouting is more stable. The development laws of settlement of all shaft grouting and end grouting pile group foundation have been changed obviously. Compared with corner pile grouting and side pile grouting, all pile group grouting is more beneficial to control the settlement and accelerate settlement stabilization.


Liu J.-F.,Southwest Jiaotong University | Zhao G.-T.,Southwest Jiaotong University | Zhao G.-T.,Beijing Shanghai High Speed Railway Co. | Ma J.-L.,Southwest Jiaotong University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2011

The soil arch in the fill on the composite pile-net foundations plays an important role in pile-soil stress adjusting and settlement control. On the basis of comparison with the existing calculation methods for soil arching effect of composite pile-net foundations, the conformation of soil arch is analyzed by single-pile numerical simulation and algebraic analysis. The analytical results show as follows: The principal stress trajectory of soil arch on pile top is a group of curves whose curvatures are growing gradually in the way from the pile top plane and in the upward direction; the principal stress trajectory near the margin of the pile cap is almost the same with the shape of a parabola which decides the height of the soil arch; the height of the soil arch is related to the friction angle of fill, the bigger the friction angle is, the higher the soil arch becomes; usually, the height of the soil arch equals to the maximum inter-pile distance. The small hole expansion theory model and parabolic arch model methods are put foward to calculate the pile-ptop pressure and the inter-pile soil pressure. The calculated results accord with the results measured on site.


Wei Q.,Southwest Jiaotong University | Wei Q.,Beijing Shanghai High Speed Railway Co. | Zhao G.-T.,China Railway Corporation | Cai X.-P.,Beijing Jiaotong University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2013

For Slab Track CRTS II, the anchorage structure behind the abutment is used, which consists of the friction plate and main end spur. In this paper the acting mechanism of the anchorage structure was analyzed, the friction force between the friction plate and bottom slab and the resistance force of soil mass were pointed out to be the main factors to keep the anchorage structure stable, and two types of buckling forms of the anchorage structure were put forward. The method for calculating resistance forces of the anchorage structure behind the abutment was presented. The formula for calculating resistance forces of soil mass in its general state, ultimate shear state and cohesion loss state was given. By utilizing the above calculation methods, the stability of the anchorage structure with the inverted T type main end spur was analyzed and the defect with the decrease of the elastic modulus of bottom slab was pointed out. Field tests verify safety and stability of the commonly used anchorage structure with the inverted T type main end spur under designed loads and point out the direction of design optimization and disadvantage of filler.


Chen H.,Southwest Jiaotong University | Ma J.,Southwest Jiaotong University | Zhao G.,Beijing Shanghai High Speed Railway Co. | Xu Z.,3rd Railway Survey and Design Group Co.
Geotechnical Special Publication | Year: 2013

In order to study the settlement characteristic of ram-compacted piles with bearing base (RPBB), pile-raft composite foundation in high-speed railway, RPBB, and Cement Fly-ash Gravel (CFG) piles were tested and compared under the Beijing-Shanghai high speed railway. Using hydrostatic levels, the settlements of test sections were monitored over the long term. Results show, because of the formation conditions and the construction technology of RPBB, the reinforced depth of RPBB is limited. Consequently, the settlement of RPBB is bigger than CFG. It also takes longer to reach stable settlement for RPBB. In addition, based on measured and modified soil compression modulus, the thicknesses of compressed layers and the settlements were calculated using control strain method and control stress method. The calculated results using control strain method and modified soil compression modulus are reasonably close to the testing data. This proves that the modified soil compression modulus can improve the precision and reliability of the settlement estimation. This can overcome the limitations of existing Chinese code. © 2013 American Society of Civil Engineers.


Liu J.-F.,Southwest Jiaotong University | Zhao G.-T.,Southwest Jiaotong University | Zhao G.-T.,Beijing Shanghai High Speed Railway Co. | Ma J.-L.,Southwest Jiaotong University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2011

The calculating method of the additional stresses in the inter-pile soil in the pile-top negative-friction segment of pile-raft composite foundation is obtained by analyzing the interaction of pile & soil in the negative friction segment at the top of the pile. On this basis, the pile-soil-cushion interaction of the composite pile-raft foundation is simulated with the spring-set model, the calculating method of the vertical effective stresses of the pile and inter-pile soil on the pile-top plane and the penetration distance from the pile-top is created. The influence of cushion on stress regulation and settlement control is analyzed. The research results show as follows: Under the action of the friction between the pile and inter-pile soil, the vertical effective stress of inter-pile soil decays with depth and to a low level at a certain depth below which the influence of pile-soil interaction on the pile-soil stress ratio at the pile top can be neglected; the modulus of the cushion plays an important role in pile-soil stress adjustment at the pile top and exerts obvious influence on the penetration amount at the pile top; the smaller the modulus of cushion, the more the penetration amount, and the penetration amount growth accelerates along with decreasing of the modulus of cushion.


Zhang J.,Beijing Jiaotong University | Yang N.,Beijing Jiaotong University | Zheng X.-K.,Beijing Jiaotong University | Luan T.,Beijing Shanghai High Speed Railway Co.
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2015

It is necessary to predict aerodynamic loads on buildings near tracks during high-speed train passage in order to design these buildings and determine their limits. An over-line bridge is a typical building near tracks, the train-induced flow and its aerodynamic effects on the bridge surface can not be ignored. Based on the wind pressure measurement test data of an over-line bridge, the measured wind pressure was transformed with wavelet transformation. The surface wind pressure fluctuation characteristics were analyzed and the wind pressure distribution in different frequency bands was identified. Analysis showed that the surface wind pressure components in lower frequency bands are larger, while those in higher frequency bands are smaller; the wind pressure energy in lower frequency bands is larger and that in higher frequency bands is smaller; the lower frequency part of the wind pressure has a larger impact on the bridge, while the higher frequency part has a smaller impact. Wavelet analysis was helpful to the study on surface wind pressure of the over-line bridge, its analysis and application techniques were worth further investigating. ©, 2015, Chinese Vibration Engineering Society. All right reserved.

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