Design Of Roadbed Environment Safety Detection Device With Freeze-thaw Cycles Based On Wireless Sensor Network

The freeze-thaw cycle is the process of the alternation of freezing and thawing. When the temperature is above 0 DEG C, the frost of surface of structure melting into water droplets, water will be permeated along the pores, or pores pathway of the surface of structure to the internal structure; when the temperature is reduced to below 0 DEG C, the water freezes and expands, when expanding force is large enough, the structure will crack, the freezing and melting of the water of surface and inner of structure will alternate appearing. It appears repeatedly, causing serious damage to the building structure.In the permafrost zones, especially seasonal frozen region, due to temperature changes under natural weather effects, with the freeze-thaw cycle, alligator crack or frost boiling are commonly found in the soils of roadbed and causing serious damage to the road structure. In order to deal with this problem, it is necessary to study the roadbed deformation under the freeze-thaw cycle, and to study the deformation mechanism, it is necessary to measure the temperature change of the freeze-thaw cycle.With the maturity of wireless network technology, the sensor has been developed to digital and small scale, which provides a new method for the measurement of roadbed environment parameters. Among them, the Bluetooth Low Energy(BLE) based on the Bluetooth 4 standard can complete many non-contact measurement tasks in some poor environment, and it is gradually be paid attention to. Bluetooth Low Energy get the reliable, standardized interoperability and wireless devices together, only one button battery can maintain it's operation for several years, which turns the continuous, dynamic detection into possible.This article combined with the National Natural Science Foundation(51378164) projects of seasonal frozen soil permanent deformation in the freeze-thaw cycle and synergistic effect of impact loading mechanism and analysis method research, from the practical demands of temperature detection in the freeze-thaw cycle of seasonal frozen soil, designs a kind of wireless small size temperature detection device based on Bluetooth Low Energy. The sensor size is only 2.5cm*2.5cm*0.5cm, which can be ignored in the size effect of the test. The mobile phone is used as a wireless receiving platform, which is free from the cable and active testing; Prepared a special APP, can be set to start or stop sampling and the sampling frequency according to their needs, it makes the sensor intelligent; It is buried in the roadbed directly, the direct measurement or node transmission measurement can be used in the depth of 30 cm and 30 cm respectively. The signal receiving is good and stable; The sample temperature ranges from-40 to 125 DEG C, it covered environmental temperature in Seasonal Frost Area fully.