Complex Rock Mass In Deep Foundation Pit Based On GPR And Elastic Wave CT 3D Geological Modeling

With the continuous and rapid development of my country’s national economy,the pace of urban construction is also accelerating.In order to solve the problem of urban traffic congestion,the development of urban underground space is speeding up.In the development of transportation,our country has made achievements that have attracted worldwide attention,and the construction of urban subways is also in full swing.In the process of subway construction,as the depth of foundation pit excavation becomes deeper and deeper,there are more and more hidden dangers of slope safety.In the actual process of deep foundation pit excavation,faced with traditional two-dimensional pictures and text data,it is time-consuming and laborious for geologists to obtain geological information in the target area.On the other hand,the complex geological structure conditions and complex site environment also greatly increase the potential safety hazards during the excavation process.Traditional planar geological interpretation is difficult to give quantitatively the spatial distribution of unfavorable geological bodies such as concealment,and qualitative interpretation cannot provide the rock mass strength parameters required for rock slope support design.Therefore,two-dimensional geological interpretation no longer meets the needs of the rapid development of urban subways,and the technology of three-dimensional geological modeling is applied.This paper takes the rock slope of the deep foundation pit of the subway as the research object.Through the establishment of a three-dimensional geological model of the abnormal body in the complex rock mass and the classification and evaluation of the quality of the rock mass,it strives for the safety of the foundation pit support design and excavation process.Sex and stability provide important guidance and reference.In general,the research work and results of this article mainly include the following aspects:(1)Through the physical experiment and numerical simulation of the ground penetrating radar,the response characteristics of typical target bodies are systematically summarized,so as to better guide the on-site measurement.Through the characteristics of reflected waves,the characteristic responses of different diseases are compared,and the unique response characteristics of karst caves and fault fissure zones are summarized,so as to accurately identify target diseases in subsequent field measurements and 3D geological modeling.(2)Through the on-site detection of ground penetrating radar and elastic wave CT,the abnormal body disease of the deep foundation pit on site can be judged from the two-dimensional profile.In terms of geological radar,the reflection profile,timedomain waveform,frequency spectrum,and wavelet time-frequency diagram are used for relevant interpretation,so as to better identify the structural characteristics of anomalous bodies;at the same time,it also provides the space for the subsequent 3D geological modeling for bad geological bodies.Coordinates provide a means for quantitative calculation.In terms of elastic wave CT,through inversion methods,the geological interpretation of the target area is given from the two-dimensional velocity profile and the three-dimensional velocity angle respectively,which in turn also provides data for three-dimensional geological modeling.(3)After identifying the disease by means of geological radar and elastic wave CT,the spatial information of the cave and the fracture surface of the fault is given,and then the spatial coordinate information of the deep foundation pit rock slope disease is compared with the three-dimensional spatial wave velocity database.The coordinate information is compared.When the position coordinates are consistent,the corresponding coordinate position and wave velocity are used as the modeling data of the rock mass disease.Then the GOCAD software is used to establish the threedimensional geological visualization model of the target detection area,and finally the three-dimensional geological data is measured by the drilling camera.The model is validated.(4)Determine the rock elastic wave velocity by core-drilling the rock masses of different depths and different lithologies in the study area,and then use the on-site measured elastic wave CT inversion to obtain the rock mass velocity to calculate the integrity index,and then combine the single Shaft saturation compressive strength,calculate the BQ value,thus give the rock mass quality classification,and give the three-dimensional visualization area for the relevant quality level.This paper has 92 pictures,17 tables and 115 references.