Development And Utilization Of Fracturing Testing Device For Tensile Strength Of Rock And Soil

Tensile strength is an important index to measure the mechanical properties of rock and soil.It is of great significance in road construction,water conservancy construction,disaster prevention and slope protection.Previous studies have mostly neglected the role of tensile strength in geotechnical engineering.With the implementation of the national strategy of "one belt and one road" and "eight horizontal and eight vertical",the problem of tensile failure of rock and soil collapse and pavement structural damage has become more and more prominent,which has aroused the concern of many scholars.At present,the traditional testing methods of rock and soil tensile strength mainly include uniaxial tension method,Brazilian splitting method,soil beam bending method,axial fracturing method and so on.On the one hand,its various testing methods not only make it difficult for relevant staff to choose appropriate testing methods in engineering practice,but also hinder the academic exchanges of relevant researchers.On the other hand,traditional testing methods have many problems,such as difficult to install sample,cumbersome operation,large man-made factors,easy to appear eccentric force and so on.In order to avoid the shortcomings of traditional tensile strength testing methods,our research group independently developed a fractured testing device for rock and soil tensile strength.Using undisturbed Malan loess,remolded Malan loess samples and the optimum sample to determine the suitable size and loading rate of the testing device.By comparing the tensile strength of gypsum samples under different dry density and different testing methods,the reliability and accuracy of the fracturing testing device for tensile strength of rock and soil are demonstrated.Specifically as follows:(1)The device mainly includes control device,mechanical mechanism,fracturing rod,sample centering frame,etc.It can record displacement and pressure data in real time,and the test object is cylindrical soil or soft rock samples.Compared with the traditional tensile strength testing device,the device integrates computer control program and mechanical structure,and avoids eccentricity and different structure fracturing rod design.The test results are accurate,and the test efficiency is high.(2)The diameter of loess sample with height-diameter ratio of 0.5 increases from 40 mm to 100 mm,and the tensile strength test value decreases first and then tends to be stable.When the diameter of the sample is 60 mm,the test results are stable.It is suggested that the diameter of 60 mm and the height of 30 mm be the optimum sample size for the testing device.(3)The test loading rate increases from 0.1 mm/min to 0.9 mm/min,and the test value of tensile strength of remolded loess increases accordingly.When the loading rate of the device is low,the test results are stable.It is suggested that 0.1mm/min be the optimal loading rate of the device.(4)Based on the fractured geotechnical tensile strength testing device,the test results of undisturbed and remolded loess samples have the same variation law,and the tensile strength of samples decreases with the increase of sample height;at the same time,it is found that the tensile strength of undisturbed samples is much larger than that of remolded samples with the same size,and there is a good negative correlation between the tensile strength and corresponding failure area of samples.(5)For gypsum specimens with the same dry density,the tensile strength of fracturing method is slightly lower than that of direct tension method,and the test results of the two methods have a good linear relationship.The test results of the fracturing tensile strength testing device are more stable,and it is more suitable for testing the tensile strength of soil and soft rock.