Lisong Zhang

Elastoplastic Analysis of Mechanical Response of Buried Pipelines under Strike-Slip Faults

AbstractA two-dimensional elastoplastic analytical model of stress–strain analysis of the pipeline under strike-slip faults was established based on the plastic flow theory and elastoplastic-beam theory, considering the effects of service loads and the nonlinearities of the pipeline and the pipe–soil interaction. According to the plastic flow theory, the axial, radial, and hoop plastic strains were derived, and the stress–strain relation was established under the plane stress state. The axial stress and strain of the pipeline induced by fault displacements were analyzed based on the elastoplastic beam theory. Additionally, the axial stresses, hoop stresses, and strains induced by the service loads (i.e., the internal pressure and the temperature variation) were also considered. The proposed model was verified by comparing the analytical results and the finite-element results. The results show that the proposed model can predict accurately the mechanical response of the pipeline subjected to strike-slip fa...

3D simulation of weak foundation for good-sized oil storage tank

The three-dimensional distributing discipline of additional stress and settlement of homogeneous soil is studied by using finite element method, for the foundation of good-sized oil storage tank. The finite element results are proved reliable and reasonable, compared with those by formula of criterion. Then, according to the geological references of Cangzhou refinery in Hebei province, the distribution of additional stress and settlement of a single oil storage tank with a volume of 15×104m3 is simulated by using the finite element method. Several disciplines on how to deal with the foundation are concluded based on the calculation results. This paper can provide reference for the analysis and design of foundation of good-sized oil storage tank.

Using the Unit Force Method to Analyze Thrust Acting on Anchor Blocks Caused by Thermal Expansion Displacement of X80 Tunnel Pipelines

AbstractTo restrict the thermal expansion displacement of X80 tunnel pipelines, anchor blocks are commonly designed and installed at entrances and exits of tunnels, which makes the anchor block design one of the most important issues. As well known, the key step for anchor block design is to calculate the thrust acting on the anchor block caused by the thermal expansion displacement. In this paper, an analysis method of the thrust is proposed, considering the effects of the vertical earth pressure, transverse horizontal earth pressure, internal pressure, temperature variation, and pipeline–soil friction. Using the condition of deformation compatibility and the hypothesis of stagnation point, the axial force of tunnel pipelines is derived by the unit force method. By combining the compatibility condition between the transition segment length of anchored side pipelines and the displacement of anchor blocks, the thrust acting on anchor block is derived. Using the analytical method and finite-element software...

Failure Classification Study of X70 Pipeline Crossing Earthquake Fault Based on Shell-Contact Model

Shell-contact theory model is studied in order to analyze axial compressive strain of X70 pipeline crossing faults on the condition of coupling between pipeline and soil, and pipeline failure classification method is proposed based on axial compressive strain. According to the magnitude of pipeline axial compressive strain, four grades of A,B,C,D are divided for pipeline failure degree, and pipeline failure classification standard is determined. Using the classification method and standard, some factors influence regulation of X70 pipeline failure degree are analyzed, such as pipeline wall thickness, buried depth, cracked zone width, slip amount, and intersection angle. Pipeline damage location and distribution scale are compared under the condition of the different parameters variation, and sensitivity of the influence factors are summarized. The results indicate that X70 pipeline failure degree decreases with the increase of fault fracture zone width; the pipeline failure degree is more strenuous on the different soil conditions of fault on both sides.

Study on Plastic Limit Load of X80 Steel Pipe Elbow with Non-Uniform Wall Thickness

The analytical formulas of plastic limit load of X80 steel pipe elbow with non-uniform wall thickness leading by production error have been established on the basis of the force balance method. The influences of external diameter (D0), rate of internal and external diameter (K), and curvature radius (R) on plastic limit load of pressurized elbow are studied. The analysis results indicate that the plastic limit load is equidirectional with the increase of the rate of internal and external diameter, and curvature radius. However, the curvature radius and external diameter have little effect on the limit load. In order to validate the accuracy of the analytical formulas, 3-D finite element model of pipe elbow has been built up. The comprehensive results show that the analytic solutions are in good accordance with the numerical solutions, which can be serviced as the foundation and reference of the calculation of pipe elbow plastic limit load in field engineering.

Combined inversion algorithm of coal seam stress field based on wavelet neural network and gradual loading algorithm

Joints extension change the physical and mechanical properties of coal due to in-site stress, then the redistribution of coal seam stress and deformation is caused, so the calculation method of coal element joints extension is given, and relationship between joints extension and stress is analyzed. Appling wavelet neural network and gradual loading algorithm, a combined inversion algorithm of coal seam stress field is presented. According to the element transition principle, the computer element program is corresponding developed, and the distribution regularity of in-site field is studied for JinCheng region in QinShui basin using combined inversion algorithm. The results show that the maximum principal stress increases from northwest to southeast in the region, and it is among 8–13Mpa; the minimum principal stress is located in Southern JinCheng, and the value is about 5–9MPa. Compared combined inversion algorithm results with measured values for the key points, the principal stress relative error is only 3%, and azimuth error is less than 1.3°. So combined inversion algorithm has higher calculation accuracy and can satisfy the engineering demand, also it has a series of advantages, such as simple model, fast calculating speed, and so on.