The Experimental Of Guide Concrete Static Cracking Test With Slit PVC Tube And Effect Analysis Of Main Crack

Exploit a mine and city many building demolition project,due to the coal rake gas broken body complex construction environment,the traditional method of blasting is limited.Static cracking technology based on static cracking agent and water reaction to produce expansion force can better solve this problem.Static cracking technology can be safe to crack without vibration,no harmful gas and no pollution.It is an important supplement and development to blasting technology.The paper tries to use the slit PVC tube to guide the fracture of the concrete block,and control the direction of the main crack.This paper studies the static cracking rule of concrete with different strength using PVC tube,and explores the reasonable fracture factor when using slit PVC tube to guide cracked concrete block.The expansion test of static cracking agent under different ambient temperature and mixing temperature is carried out.The water agent ratio is 0.25,0.26,0.27 and 0.28 respectively.Under the same ambient temperature and the same mixing water temperature,the maximum volume expansion rate of the static cracking agent was 4.59 when the ratio of water agent was 0.25.Firstly,a single hole concrete block with different strength of 200 mm×200 mm×200 mm was taken as the test object,and the single hole concrete block was guided to crack by slit PVC tube.The concrete strength grades are C30,C40 and C50 respectively.The results of non static cracking test of single hole concrete block with different strength were taken as control group.The fracture modes of single hole concrete block with different strength were analyzed by using slit PVC tube under guide and non guided static fracture.The test results show that when the slit PVC tube is used to guide static cracking,the initial position of cracks can be controlled,and some other cracks around boreholes will be reduced to a certain extent.In addition,when the slit PVC tube is used to guide static fracture,the cracking time will be prolonged and the maximum crack width will be reduced.On this basis,the test of double hole concrete with different strength is taken as the test object,and the pilot crack and the non guide static cracking test of the slit PVC tube are carried out.The reasonable fracture coefficient of the slit PVC tube oriented cracking concrete was explored with the hole distance of 160 mm,180 mm and 200 mm as variables.In addition,the strain gauge is arranged on the surface of the slit PVC tube oriented crack concrete test block to verify the guiding process of the main crack.The experimental results show that the slit PVC tube can achieve the main crack direction effectively while guiding the static cracking concrete.Meanwhile,it can effectively reduce cracks in the direction of the non PVC tube joint,and also inhibit the crack propagation in the direction of the non cutting seam.Under the combined action of two holes,the reasonable cracking coefficient is about 5.5 when using the slit PVC tube to guide the concrete block.With the increase of the hole spacing,the main crack formation process slows down,and the effect decreases.The strain and time variation curve verify the process of the main crack in the cracked concrete block of the slit PVC tube.