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The deformation of the overlying pipeline caused by the soil tunnel excavation cannot be ignored in the case of the small spacing between the pipeline and the tunnel. Based on the rigid bar method, the pipeline-soil interaction model was established, with the simply supported beam as the basic system, and the loads acting on the pipeline by the soil are considered to be linearly distributed. Calculation methods for continuous and discontinuous pipeline deformations were established. The results calculated by the proposed method agree well with the experimental data of centrifuge tests and field data. Parametric study on the effect of the volume loss (η = 1%, 2%,3 %), rotational stiffness (β0 = 4.47 × 106N⋅m/rad, 4.47 × 108N⋅m/rad, 4.47 × 1010N⋅m/rad), ratio of pipeline section length to inflection point of soil settlement curve (L/is = 0.5, 1.0, 1.5, 2.0) and soil elastic modulus (E = 10 MPa, 30 MPa, 50 MPa) on the deflection and joint rotation angle of the discontinuous pipeline were carried out. Results show that: (1) the maximum pipeline deflection and the maximum rotation angle of the joint increase as η increases and decrease as β0 increases; (2) in the "odd" case, the maximum pipeline deflection and the maximum rotation angle of the joint first increase and then decrease as L/is increases, reaching a peak at L/is = 1.5, while in the "even" case, the maximum pipeline deflection decreases as L/is increases and the maximum rotation angle of the joint first increases and then decreases as L/is increases; (3) in the "odd" case, the maximum pipeline deflection and the maximum angle of rotation of the joint decrease as E increases, while the opposite trend is observed in the "even" case. Additionally, the maximum pipeline deflection and the maximum rotation angle of the joint are always greater in the "odd" case than that in the "even" case. [ABSTRACT FROM AUTHOR]

The deformation of the overlying pipeline caused by the soil tunnel excavation cannot be ignored in the case of the small spacing between the pipeline and the tunnel. Based on the rigid bar method, the pipeline-soil interaction model was established, with the simply supported beam as the basic system, and the loads acting on the pipeline by the soil are considered to be linearly distributed. Calculation methods for continuous and discontinuous pipeline deformations were established. The results calculated by the proposed method agree well with the experimental data of centrifuge tests and field data. Parametric study on the effect of the volume loss (η = 1%, 2%,3 %), rotational stiffness (β0 = 4.47 × 106N⋅m/rad, 4.47 × 108N⋅m/rad, 4.47 × 1010N⋅m/rad), ratio of pipeline section length to inflection point of soil settlement curve (L/is = 0.5, 1.0, 1.5, 2.0) and soil elastic modulus (E = 10 MPa, 30 MPa, 50 MPa) on the deflection and joint rotation angle of the discontinuous pipeline were carried out. Results show that: (1) the maximum pipeline deflection and the maximum rotation angle of the joint increase as η increases and decrease as β0 increases; (2) in the "odd" case, the maximum pipeline deflection and the maximum rotation angle of the joint first increase and then decrease as L/is increases, reaching a peak at L/is = 1.5, while in the "even" case, the maximum pipeline deflection decreases as L/is increases and the maximum rotation angle of the joint first increases and then decreases as L/is increases; (3) in the "odd" case, the maximum pipeline deflection and the maximum angle of rotation of the joint decrease as E increases, while the opposite trend is observed in the "even" case. Additionally, the maximum pipeline deflection and the maximum rotation angle of the joint are always greater in the "odd" case than that in the "even" case. [ABSTRACT FROM AUTHOR]

The existing tunnel construction causes stratum deformation, which in turn leads to additional deformation and internal force of the overlying pipeline, thus increasing the risk of pipeline accidents. Then, how to correctly calculate the deformation and internal force of pipeline is the key to pipeline safety evaluation. To this end, this study firstly used the Pasternak foundation beam model to simulate the interaction of pipeline and soil, and divided the pipeline into the void area (i.e., pipeline-soil detachment) and the coordination area (i.e., pipeline-soil is always deformed together) between pipeline and soil. The differential equation of pipeline deflection for the void area and the coordination area were established respectively, and the solutions of pipeline deflection, the internal force of pipeline and the width of pipeline-soil void area were presented. Subsequently, the accuracy of the proposed method was verified by comparing with the available model and field test data, and it is found that the calculation results are too conservative without considering the pipeline-soil voiding phenomenon. Finally, the detailed parametric analysis was conducted. The results show that the pipeline deflection decreases with the increase of the pipeline-tunnel spacing between pipeline and tunnel, the pipeline bending stiffness and the soil elastic modulus, but increases with the increase of the formation loss rate, and the width of pipeline-soil void area increases with the increase of the pipeline-tunnel spacing, the pipeline bending stiffness and the soil elastic modulus. [ABSTRACT FROM AUTHOR]

Affected by climatic conditions such as rainfall, evaporation and air temperature, most of the backfill soil is in an unsaturated state, and the decrease in matric suction leads to the failure of the retaining structure. In view of this, this study takes the vertical rigid retaining wall with narrow unsaturated backfill as the research object, assuming that the backfill behind the wall forms a circular soil arch and considering the interlayer shear stress; thus, the analytical solution of the active earth pressure of narrow unsaturated soil is derived based on the thin layer element method. The reliability of this method is verified by comparing with the experimental and existing theoretical results. A parameter analysis demonstrates that with the increase in the interface friction angle of the moving wall–soil, the average shear stress coefficient of zone I and zone II increases gradually, but with the increase in the interface friction angle of the fixed wall–soil, the average shear stress coefficient of zone I decreases; with the increase in effective internal friction angle and effective cohesion, the active earth pressure decreases and the tension crack depth increases; with the increase in the interface friction angle, the active earth pressure in the upper part of the retaining wall increases slightly, while the active earth pressure in the lower part decreases obviously; with the increase in matric suction, the active earth pressure first decreases rapidly and then increases gradually, and the tension crack depth first increases and then decreases, but the distribution pattern of the horizontal active earth pressure remains unchanged; the active earth pressure decreases with the decrease in the aspect ratio, and when the aspect ratio is smaller, the attenuation is more obvious; until the aspect ratio reaches a certain value, the active earth pressure is basically unchanged. [ABSTRACT FROM AUTHOR]

Headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) has been applied to the determination of the volatile compounds of a common traditional Chinese medicine , Flos Chrysanthemi indici. Twenty-six compounds were identified by the present method, which are similar to the results from steam distillation. Difference in analysis from ten growing areas was found to be in their relative content and total concentrations. Four active compounds (cineole, 3-thujanone, borneol and bornyl acetate) were applied to the evaluation of the quality of Flos Chrysanthemi indici from different areas. By comparing their peak areas, it was found that Flos Chrysanthemi indici with the best quality was from Hangzhou in China. These results show that HS-SPME-GC-MS is a simple, rapid and solvent-free method for the analysis of the volatile compounds in this material and a potential tool for its quality assurance. [ABSTRACT FROM AUTHOR]