温度对应变计测量钢支撑轴力的影响

Influence of Temperature on Measuring Axial Force of Steel Support with Strain Gauge

钢支撑是目前地铁基坑的重要组成部分,准确测量出支撑轴力可为判断基坑安全提供重要依据。然而,受温度影响,目前采用表贴式应变计难以对钢支撑轴力进行准确监测。因此,文章分析了温度对表贴式应变计和钢支撑轴力的影响,说明目前所采用的温度修正公式存在一定的局限性,分析了在不同侧限条件下,温度变化对钢支撑轴力的影响,得到主要结论如下:①目前应变计厂家给出的应变计温度修正公式的前提条件为:钢支撑受温度影响后,温度改变产生的应力与变形能得到完全释放;②只有考虑钢支撑两端无侧限,才可采用目前修正公式计算支撑轴力;③实际工程中,钢支撑两端变形受到墙后岩土体的限制,若按照目前的应变计计算公式对钢支撑轴力进行计算,将会产生一定的误差。且若墙后岩土体的刚度越大、支撑越长,则产生的测量误差越大。

Steel bracing is an important part of subway foundation pit at present,and accurate measurement of supporting axial force can provide an important basis for judging the safety of foundation pit.However,due to the influence of temperature,it is difficult to accurately monitor the axial force of steel support with surface mounted strain gauges at present.Therefore,analyzes the influence of temperature on the surface mounted strain gauge and the axial force of the steel support,indicating that the current temperature correction formula has some limitations,and analyzes the influence of temperature change on the axial force of the steel support under different side limit conditions.The main conclusions are as follows:①The premise of the current temperature correction formula of the strain gauge given by the strain gauge manufacturer is:after the steel support is affected by temperature,The stress and deformation caused by temperature change can be completely released.②Only considering that there is no lateral limit at both ends of the steel support,the current modified formula can be used to calculate the support axial force.③In practical engineering,the deformation of both ends of the steel support is limited by the rock and soil behind the wall.If the axial force of the steel support is calculated according to the current strain gauge calculation formula,there will be some errors.And if the stiffness of rock and soil behind the wall is larger and the support is longer,the measurement error will be larger.