Rock Mass RQD Acquisition Based On Digital Close-range Photogrammetry

In recent years,with the rapid development of China's economic construction and the continuous improvement of the city's cultural level,many large-scale projects such as water conservancy and hydropower,transportation and energy,and urban construction have been built.In many cases,rock masses are involved.As for the stability of the slope,the stability evaluation of rock slopes is of great significance to safeguarding people's lives and property safety.The stability evaluation of rock slopes is of great significance to guarantee the safety of people's life and property.The information of the discontinuity of rock mass is an important factor in controlling slope stability.Therefore,in the evaluation of rock slope stability,a large number of random rock mass discontinuities should be investigated first.The traditional survey method of the information of rock mass discontinuities is mainly based on the artificial compass contact measurement.Because this method is directly measured in contact with the discontinuity of rock mass,it is currently a more reliable rock mass discontinuities information acquisition method.However,this method has the disadvantages of large labor intensity,low efficiency,collection scope,and limited information obtained,especially in high and steep slopes and metal ore slopes.The application of this method is limited to a great extent and cannot meet the engineering exploration demand.Therefore,digital close-range photogrammetry technology has been applied to engineering geological survey work by virtue of its advantages such as non-contact measurement,high measurement speed,high precision,and large amount of information,etc.,opening up a new dimension for traditional engineering geological surveys.Ideas,new methods.After a long period of theoretical research and engineering practice by many experts and scholars,the technology for obtaining information on the discontinuity of rock slope by using digital close-range photogrammetry methods has matured and can exert its advantages in engineering practice.Accurately obtain relevant information and provide a reliable and accurate data base for the stability evaluation of rock slope.The stability evaluation of rock slope is mainly based on the quality evaluation of rock mass.The parameters that characterize the rock mass include the orientation,track length,connectivity,and Rock Quality Designation(RQD)et al.,among which RQD is an indicator that reflects the integrity of the entire rock slope and is important for stability evaluation of rock slopes.Based on this,it is of great significance to obtain an accurate and reliable RQD for the evaluation of rock slope stability.For the acquisition of RQD,a lot of researches on domestic and foreign scholars have also conducted studies on probabilistic model method,three-dimensional modeling of rock discontinuity network,and the sample window method to obtain RQD.In a comprehensive comparison,the RQD obtained by the error of the model generated by the probabilistic model method and the network simulation method is difficult to be used as an indicator for the overall quality evaluation of the rock mass;the RQD obtained by the sample window method cannot truly reflect the three-dimensional space state of the rock mass.Digital close-range photogrammetry has the advantages of remote measurement,low cost,easy implementation,low labor intensity,access to panoramic outcrop date of the rock slope,etc.,and conducts research on rock mass RQD acquisition based on digital close-range photogrammetry,and intends to improve RQD acquisition from data acquisition and method models.In this paper,Changchun Jingyue Dongsheng Quarry is taken as the research area.Based on the digital close-range photogrammetry technology,the non-contact measurement of rock slopes reveals a large amount of spatial trace length and orientation information of the discontinuity of rock mass and the three-dimensional coordinates of the traces are respectively projected.To the three projection planes of YOZ,YOX,and XOZ,the RQD values on each projection plane are calculated by using different distances to lay out the lines in different directions,and then the comparison and analysis are performed,and the weighted average is used to obtain the RQD value.When the three-dimensional data of the trace is acquired,the blank area that can't be collected due to vegetation and collapsing gravel is judged by judging the intersection relationship between the survey line and the blank area,eliminating the influence of the blank area,and then effectively calculating the RQD value,greatly increasing the accuracy of RQD values educes calculation errors.In this paper,we also study the effect of different direction lines and line spacing on RQD,and find that RQD has a significant scale effect.At the same time,the discontinuity of rock mass are grouped according to their orientations,and the average spacing between the discontinuity of rock mass of each group is calculated to provide a reliable parameter basis for the quality assessment of fractured rock masses.Overall,this paper has obtained the following research results:(1)Acquisition of the information of the discontinuity based on digital close-range photogrammetry.Digital close-range photogrammetry to obtain the information of the discontinuity is divided into field work and internal work.The field work mainly includes the control measurement of the spatial polar coordinate method based on the free prism,and the image acquisition and correction of the slope.The internal work mainly includes the three-dimensional modeling of the slope based on digital photogrammetry workstation VirtuoZo and the information interpretation of the model based on spatial coordinates.Research shows that this method can quickly obtain a large amount of random information of the discontinuity.(2)The weighted RQD acquisition of the three-view projection.Propose the "three-two-three" method that is,to project complex three-dimensional problems onto three mutually perpendicular planes,laying different lines in different directions below each projection plane,and determine the projection planes according to the distribution area of each projection plane trace.The weight coefficient of the RQD value is weighted and averaged for each projection plane RQD,and the two-dimensional problem is converted into a three-dimensional problem to obtain a weighted RQD with three-view projection as an indicator for evaluating the integrity quality of the rock mass.(3)Improvement of RQD model that takes into account the influence of the blank area.For blank areas where vegetation and collapsing gravel are blocked and the information of the discontinuity cannot be collected,by judging the intersection relationship between survey lines and blank areas,an improved RQD model that takes into account the effects of blank areas is proposed.The obtained RQD and the effect of not taking into account the blank area are obtained.The comparison of RQDs found that the presence of the blank area has an effect on RQD at about 10%,affecting the grade of rock mass evaluation.(4)Study on the scale effect of line spacing.The RQD was obtained by measuring the lines with different spacing and direction.It was found that the RQD changes significantly with the change of the line spacing,so the line spacing has a scale effect.The RQD value of the projective planes changes at about 1% when the distance between the measured lines is 0-1m,and the RQD value is stable.The RQD value of the projective plane changes at about 12% when the distance between the measured lines is between 1m and 4m,and the RQD value varies greatly;therefore for this slope,1m is the best line spacing.The research results have theoretical and engineering practical significance.