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Liu R.,Tianjin University | Li B.,Tianjin University | Wang H.-B.,Tianjin University | Zhang J.,Tianjin University | Xu Y.,Tianjin Architecture Design Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

In-service hydrocarbons must be transported at high temperature and pressure to ease the flow and prevent solidification of the wax fraction. The buckling of submarine pipelines occurs due to the introduction of axial compressive forces caused by the constrained expansions set up by thermal and internal pressure actions. Vertical buckling is particularly of interest with respect to buried submarine pipelines. To lay pipeline in trench with a certain depth is an effective measure to avoid vertical thermal upheaval buckling. Therefore, it is very important that study of the maximum resistance which soil can provide as well as the soil resistance changing procedure with the pipeline buckling amplitude. Fine sand was chosen as the soil medium in view of Bohai Gulf conditions. A model test was carried out to establish the relationship between soil resistance and pipeline displacement in laboratory. The pipeline segments with different diameters and different covered depths were used in the test. The soil resistance and the pipe segments vertical displacement were both recorded in great details. Then the numerical analyzing methodology was applied to simulate the model test procedure. Test data and analyzing results show that when the pipeline doing vertical uplift movement, process of soil resistance exertion can be affected by the buried rate of pipeline, when the buried rate is small, soil resistance decreases until stable after reaching peak; while when buried rate is large, the soil resistance doesn't significantly reduced after its peak. In the practice, the maximum soil resistance can be gained when the pipeline upward displacement reaches to approximate 0.1D. Source

Sun L.-Q.,Tianjin University | Yan S.-W.,Tianjin University | Xu Y.,Tianjin Architecture Design Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

The deformation is the dominant factor of the quality of the road constructed on the soft soil foundation. Tianjin Dongjiang port is located on the hydraulic filled soil foundation which is improved by using vacuum preloading method. Roads in this area often suffer wave type asymmetry settlement, which seriously affects the usage of the road and causes damage to both vehicles and human being. It is found that the initial wave asymmetry deformation of the road on very soft soil foundation is usually existing and will be developing continuously under the traffic load. The mechanism of the wavy failure of the road is discussed by establishing a mechanical model. The method of using geogrids to reduce the asymmetry deformation is proposed; the reinforcing effect is analyzed using finite element method. Source

Li R.,Tianjin University | Liu R.,Tianjin University | Xu Y.,Tianjin Architecture Design Institute | Lin M.-B.,Tianjin University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Vehicle bumping at bridge head is a common quality problem in highway construction on soft soil foundation. Reasonable transition of flexible and rigid foundations is the core of solving this problem. On the basis of summarizing the relavent research results, the cement-mixing-pile-foundation treatment scheme adopted in the connection area of bridge and highway project in Tianjin is simulated by ABAQUS. The influences of treatment scope, gradient of pile length and variable pile length on eliminating the first and second vehicle bumpings are analyzed. The results show that cement mixing pile method is very effective in eliminating the vehicle bumping at bridge head. With the enlargement of the length of treatment scope, differential settlement also increases slightly, but the vehicle bumping at the section between the treated and untreated area can be alleviated. The increase of the pile length ratio in the highway extension direction will alleviate the vehicle bumping both at bridge head and in the section between treated and untreated areas. The increase of the length of cement mixing pile will aggravate the vehicle bumping at the section between the treated and untreated areas. Source

Liu H.,Tianjin University | Liu B.,Tianjin University | Li X.,Tianjin Architecture Design Institute
Wuhan Ligong Daxue Xuebao (Jiaotong Kexue Yu Gongcheng Ban)/Journal of Wuhan University of Technology (Transportation Science and Engineering) | Year: 2012

In order to study the pressure loss of Trifluoromethane fire-extinguishing system, on the basis of experimental and theoretical analysis, the CFD simulation and the pressure loss calculation have been proposed and established, and then the new formula was gotten and then verified through experiments .The results show that the method of pressure loss calculation based on CFD, is visual, high reliable, and can more accurately describe the pressure loss. Source

Liu R.,Tianjin University | Yan S.-W.,Tianjin University | Wang H.-B.,Tianjin University | Zhang J.,Tianjin University | Xu Y.,Tianjin Architecture Design Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

Buckling of submarine pipelines may occur due to the action of axial soil frictional force caused by relative movement of soil and pipelines, which is induced by the thermal and internal pressure. The buckling may take place either laterally or vertically. The likelihood of occurrence of the buckling phenomenon is largely determined by the capability of the soil to resist pipeline movements. A series of large-scale model tests are carried out to facilitate the establishment of substantial data base for a variety of burial pipeline topologies. Fine sand is chosen as the supporting medium in view of Bohai Sea geotechnical conditions. Dry testing is employed for convenience. The pipes with diameters of 30 mm, 50 mm and 80 mm are used respectively. The pipes are buried in different depth-to-diameter ratios between 1 and 9. The uplift, lateral and axial resistances are recorded during the tests. Results show that the soil resistance depends on the pipe diameters and cover depth. For the same cover depth, the lateral soil resistance is more than twice as the uplift one. Based on the observed data, empirical formulas are established. Source

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