Experimental Study On Crack Development Of Compacted Expansive Soil Under Different Temperature And Humidity

Temperature and humidity are the main factors of climatic,and also the important factors leading to soil cracking.Experimental study on the growth of expansive soil cracking under different temperature and humidity conditions can be conducive to knowing about the development mechanism of cracking,and providing the basis for solving the problems of expansive soil in practical engineering.Taking the expansive soil of Nanyang Expressway as the research object,the growth of compacted expansive soil under different temperature and humidity conditions,studied by experiments and recorded by taking photographs.Cracks image processing using photoshop and matlab,and make a quantitative analysis of the characteristic parameters of expansive soil crack development,The main contents are as follows:(1)Studied the method of obtaining high quality expansive soil image and improved the method of image processing.When selecting the appropriate external light source,we can get a more uniform image;crack image processing results show that,there is few difference between the white and yellow light source.Camera pixel has a great influence on the accuracy of the binarization,and the higher the pixel is,the crack image is more clearer and the result is more accurater.The threshold of binarzation and the area threshold for removing impurities have a great influence on the processing result,and suggested to use the Photoshop software to cut out the image,then adjust the threshold and compare with the original image to determine the best threshold.Adjust the brightness of some lower or higher grey level part in the image,than get the ideal binary image.(2)The experimental investigation on the growth of compacted expansive soiling cracking under different temperature and humidity conditions is conducted.The experimental results are as follows:the development process of crack can be divided into the development stage of fracture length,the crack width development and the stable stage.when under same temperature and he humidity is lower,at the initial stage,the fine cracking advances rapidly,and all characteristic parameters of cracks increase rapidly,in the later period,all characteristic parameters of cracks were larger.When under different temperature conditions:the humidity is relatively low,the development speed of all parameters of cracking at initial stage is close.The lower the temperature is,the greater the crack rate is;the cracking branch number and the peak value of cracking length are bigger;the width of cracking width is smaller;the temperature in the later period is lower;the crack rate and the average width of cracking is greater,while the cracking branch number and the total cracking length is smaller.When the humidity is relatively high,the higher the temperature at the initial stage is,the faster the development speed of crack rate is and the bigger the peak value is;the faster the development speed of the cracking branch number and the total cracking length is,the bigger the peak value is.While the temperature in the later period is higher,all characteristic parameters of cracks are smaller.