With the development of petroleum and natural gas resources, pipeline transportation has become one of the main transportation modes. Pipeline leakage caused by various external factors during transportation affects the safe running of the pipeline. The development of optical fiber sensing technology has brought a new solution for pipeline leakage monitoring. Most of the existing research are carried out by numerical simulation work,lacking experimental demonstration,and only studied the temperature field distribution in the soil area after pipeline leakage,without taking the impact of the difference in soil internal physical properties on the temperature change into account. In addition,the accuracy of the monitoring of small leaks still can't satisfy the monitoring requirements. And the conventional fiber arrangement is only suitable for monitoring the temperature along the line,when the surface of the object to be measured is large and the monitoring requires a higher spatial resolution,the one-dimensional laying method is difficult to achieve the required resolution,it needs to be optimized. Based on the advantages of high spatial resolution of optical frequency domain reflectometry technology,in this paper,we mainly focus on oil and gas pipeline monitoring wiring problem and build a sandbox model with a small proportion. On the basis of one-dimensional tiled line monitoring,a new way of laying optical fiber for sinusoidal surface monitoring is proposed. Using optical frequency domain reflectometry technology with high spatial resolution as a supporting tool,the superiority of sinusoidal layout is verified. The results show that the measurement effect of buried optical fiber with a sinusoidal layout is better than that of a conventional one-dimensional tiled layout because of its wider measurement range. We analyzed the effect of sinusoidal period and longitudinal length on temperature monitoring,these two factors have a greater effect on the monitored maximum temperature,which means the larger the sine period and vertical length,the lower the highest temperature detected. Therefore,if there is no precision requirement,the optical fiber can be arranged long and sparse. Otherwise,it needs to be even tighter. Through the combination of experiments and numerical simulations, it is obtained that the maximum thermal influence radius of the tiny heat source is 7 cm,and this result can further guide to optimize the arrangement of optical fiber. In addition, the relationship between soil thermal conductivity, soil bulk density,and water content is obtained by the variable method. The relationship between soil bulk density and soil thermal conductivity is basically linear,the relationship between soil thermal conductivity and water content is not a specific linear increasing or decreasing trend,it varies in a parabolic- like form with the influence of external factors. Water content also affects the vertical distribution of the soil temperature field. When the water content is below the threshold,as it increases the rate of soil heat transfer in the vertical direction becomes faster,the temperature around the heat source increases faster,the maximum temperature monitored becomes larger, the high temperature influence range becomes larger, and the degree of heat diffusion increases significantly. We have studied the effect of heat source temperature on soil heat transfer,and found that as the heat source temperature increases,the heat diffusion range becomes larger,the high temperature influence range becomes larger,and the distance of temperature transfer in the vertical direction becomes farther. The influence law of these factors on soil heat transfer provides a reference for pipeline leakage monitoring,which can further guide the fiber arrangement. Meanwhile,it also verifies the feasibility of optical frequency domain reflectometry distributed optical fiber technology can accurately measure soil temperature field and also provides guidance for other distributed temperature measurement technologies in the layout of buried optical fibers.
