Collapsible loess is prone to self weight collapse after soaking. The strength of loess will be greatly reduced, and it will threaten the safe operation of buried pipelines along the way. In order to study the stability of buried pipelines in collapsible loess regions, the displacements, stresses and strains of different pipe outer diameters and wall thicknesses during collapsing were analyzed based on the finite element method. The limit length that the buried pipeline could withstand in the loess disaster under certain conditions was obtained by the eigenvalue buckling theory. The results show that: increasing the outer diameter and wall thickness of the pipeline and reducing the buried depth of the pipeline in the loess can effectively reduce the displacement of the pipeline in the collapsible loess; and increasing the outer diameter and wall thickness of the pipeline can also effectively avoid the phenomenon that the local stress of the pipeline is too high; the maximum stress and strain of the pipeline occur at the center of the collapsing zone and the fixed ends on both sides; according to the buckling eigenvalue theory, the ultimate length of the collapsible area of the pipeline is about 65 m when the soil mass has self weight collapsible, and increasing the outer diameter and wall thickness of the pipeline can enhance the buckling resistance of buried pipelines when self weight collapse after soaking.

Microbes can improve the fluidity of waxy crude oil and increase the efficiency of transportation. The cultured Bacillus subtilis 6# and Pseudomonas aeruginosa 3# were mixed and cultured in a ratio of 2∶3, the growth conditions were optimized. DSC, polarizing microscope, HAKEE rheometer and interfacial tensiometer were used to analyze the effect of compound bacteria and waxy crude oil. The results showed that: after treatment with compound bacteria, the wax precipitation point of waxy crude oil decreased by 2.23 ℃, the peak point of wax precipitation decreased by 2.71 ℃, and the wax content of crude oil decreased by 51.64%; the wax crystal structure changed significantly; the apparent viscosity of crude oil decreased by 64.72% at 37 ℃. In addition, the emulsification index of the compound bacteria on liquid paraffin was 55.39%, and the surface tension of the liquid paraffin culture medium was reduced from 79.89 mN/m to 38.83 mN/m. Compared with single bacteria, compound bacteria are more effective in removing wax and reducing viscosity, and have wider application prospects.

Nb2O5/SBA-15 catalyst was prepared by impregnation with mesoporous molecular sieve SBA-15 as the carrier, and characterized by XRD, BET and other methods. The results show that catalyst Nb2O5/SBA-15, a highly ordered two-dimensional hexagonal mesoporous structure，has larger specific surface area，pore size and pore volume. The catalytic capability of Nb2O5/SBA-15 was studied for esterification, and the optimum reaction conditions were found as follows：n(methanol)/n(oleic acid)=2∶1，reaction temperature 160 ℃，reaction time 4 h，ratio of catalyst to reaction 9.10%. Better reuse ability of Nb2O5/SBA-15 can be also obtained, which confirms Nb2O5/SBA-15 a suitable catalyst for the esterification．