Advanced Geological Prediction Research Articles

Study on the Influence of different factors on cutterhead shield jamming of gripper TBMs in weak rocks

In the construction of deep-buried and long-mileage tunnels, the use of tunnel boring machines (TBMs) is the preferred excavation method. However, TBMs encounter a variety of problems in adverse geological conditions. When excavating in weak rocks with high in situ stress, the large deformation of the surrounding weak rocks causes TBM jamming, which is very time consuming and expensive to deal with. In practice, the most commonly used method is the advanced geological prediction technology, and support systems are strengthened on the basis of the convergence–confinement method, which is composed of the longitudinal deformation profile (LDP), ground reaction curve, and support characteristic curve. In this work, the LDPs of surrounding weak rocks were obtained using numerical models in FLAC3D. The influence of the elastic modulus (E) of rocks, buried depth of a tunnel (BDT), and tunnel diameter on the cutterhead shield jamming of a gripper TBM was analyzed. In the analysis, the total length of the cutterhead and cutterhead shield of the gripper TBM was 4 m, and the friction between the cutterhead shield and the surrounding rocks was not considered. Results showed that increasing the overcut was the most effective method to prevent TBM jamming. Moreover, E and BDT exerted an obvious effect on the design value of the overcut. Several suggestions to prevent the cutterhead shield jamming of gripper TBMs and countermeasures to resolve such jamming in weak rocks were subsequently derived. The conclusions of this work can facilitate the selection of appropriate overcuts when designing the cutterheads of TBMs and help to prevent and control the cutterhead shield jamming of gripper TBMs in weak rocks.

Complex 3D geological modeling based on digital twin

With the development of digital twin and multi-source data fusion technologies, objectively and accurately reflecting the complexity of geological structures has been the key to the development of geological modeling. Therefore, a complex 3D geological modeling method based on digital twin is proposed. Integrating multi-source data, the method realized 3D modeling of geological body containing complex structures through potential-field interpolation based on cokriging algorithm. Combined with real-time sampling data such as geological sketch of palm surface and advanced geological prediction obtained during the construction process, the 3D geological model was locally corrected to achieve a realistic approximation of the newly revealed geological conditions. The results show that the digital twin geological model can reasonably and effectively use multi-source and multi-scale geological information to truly reflect the 3D spatial characteristics of complex geological structures. It also reflects the refined process of geological model before and after the engineering construction, and provides effective safety guarantee for the tunnel and underground space engineering in the construction and operation stages.

Case Study on the Stability Control of Broken Surrounding Rock in Roadway Excavation on the Edge of a Collapsed Stope Area

Predicting and controlling the collapse of surrounding rock (especially broken rock masses) in underground chambers is an important topic in mining and geotechnical engineering. Based on an example, this paper introduces a case study of surrounding rock stability control technology in stope mining around abandoned areas. Based on on-site coring, mechanical properties of rock samples, and on-site grouting reinforcement technology, the TRT6000 advanced geological prediction system was used to predict the stability status of the surrounding rock of the underground chamber. AUTODYNA software was used to build a dynamic coupling model for numerical simulation prediction and optimization of blasting parameters and to reveal the dynamic variation in the surrounding rock. The dynamic failure process of the surrounding rock of the chamber before and after optimization of the blasting parameters is simulated, and the deformation characteristics and damage and acoustic emission characteristics of the surrounding rock are clearly shown. The surrounding rock failure first appeared around the surface of the underground chamber because of the high stress concentration around the surface of the chamber after blasting; with the interaction between the explosive gas and the rock mass, the damaged area further propagated into the external rock, eventually leading to a large damage area. At the same time, there is a large tensile failure in the rock, resulting in expansion and rupture around the underground chamber. Finally, the 3D laser scanning method is used to verify the superiority of the optimized blasting initiation sequence. The new edge hole detonation sequence can effectively improve the blasting vibration and successfully control the further damage of the surrounding rock of the underground chamber, thus proving the edge hole drug pack. Moreover, the initiation mode of the delay stage of the side hole charge is determined. This study provides a useful reference for the stability control of surrounding rock in mining in mining areas.

Application of Advanced Geological Prediction in Tunnel Construction

Application of Advanced Geological Prediction in Tunnel Construction

Collapse risk assessment of deep-buried tunnel during construction and its application

The hazard of tunnel collapse is a key factor restricting the excavation progress and safety of the tunnels excavated by drilling and blasting. To control this construction risk, a new risk assessment method of tunnel collapse involving case analysis, advanced geological prediction, and Dempster-Shafer (D-S) evidence theory is put forward. At first, after analyzing the typical tunnel collapse cases, 11 influencing factors were adopted as the risk evaluation indices from the natural environment, engineering geological conditions, design and construction, organization and management, as well as advanced geological prediction. Further, the risk indices and their corresponding ratings are calculated to establish the assessment index system. Secondly, for calculating the index weights, the Euclidean distance based on the number of intervals is applied for obtaining the basic probability of each index belonging to each risk grade. Furthermore, the index weights are determined depending on the degree of similarity and support between the indices. Thirdly, the tunnel collapse risk level is obtained based on the D-S fusion rule. In this way, the theory and technical system of risk control of tunnel collapse are established. Finally, the established risk assessment method of tunnel collapse is successfully applied to the Yuxi tunnel. The consequent result is in perfect accordance with the practical condition which suggests that this approach is reliable and practical. This study provides references for other similar tunnel constructions.

Analysis on Security Risks in Tunnel Construction Based on the Fault Tree Analysis

Since tunnel engineering, as a kind of underground construction, has huge security risks, it is very important to evaluate the safety risk of tunnel construction stage. It cannot only provide basis for risk control but ensure construction safety. Taking Qingpingchuan tunnel as an example, the WBS-RBS method is employed to identify the construction risk of the tunnel and the identified risk sources are used to analyzed qualitatively and quantitatively with fault tree theory. Finally, we can conclude that the critical factor affecting the collapse of Qingpingchuan tunnel is the instability of surrounding rock, and that the secondary critical factor lies in the inconsistence of the soil quality with the survey documents, low effect of waterproof and drainage facilities, weak strength of pre reinforcement, excessive steps of excavation cycle, unqualified support construction, inaccurate advanced geological prediction, etc.

Application of comprehensive advanced geological prediction technology in Da-puling tunnel

For the Da-puling tunnel of Puqing Expressway in Guangxi, the advanced geological prediction is carried out by combining TSP long-distance forecast method with short distance geological radar method. This paper describes the principle of seismic wave propagation in elastic medium, as well as the key points of data processing and analysis, some requirements that should be paid attention to the field test and scientific way of image interpretation put forward to improve the accuracy of prediction; When TSP is deployed, it should be sharp angle with potential joint surface. P-wave reacts surrounding rock properties, the shear wave is closely related to the transverse skeleton of medium. In data interpretation, it is necessary to focus on the analysis of the characteristics of P-wave and S-wave, weakening Poisson’s ratio and Young’s modulus. TSP and GPR can achieve the mutual complement and improve the detection accuracy.

Application of a new seismic reflection imaging system TSP-SK in tunnel advanced geological prediction

When there are water rich-karst caves or large faults in front of the tunnel face, blind construction may easily cause safety accidents such as water inrush, mud outburst and collapse. Using advanced geological prediction methods to predict the spatial distribution of unfavorable geological bodies can greatly reduce construction risks. This paper introduces a new seismic reflection imaging system TSP-SK, and discusses the features, working mode and data processing methods of the prediction system, and verifies the reliability of TSP-SK through practical tunnel engineering prediction case. The result shows that TSP-SK can collect high signal-to-noise ratio seismic reflection data with little interference from clean first arrival when the water sealing effect of explosives in the borehole is good. Good reflection wave pickup effect can be obtained when the maximum gain of inverse Q filter and Q value are taken in the range of 15 to 30. The prediction results of TSP-SK are in good agreement with the actual excavation results, that is, the areas with low P-wave velocity indicate poor rock mass quality, and the area of low S-wave velocity is more likely to produce water from construction.

Accuracy Evaluation of Advanced Geological Prediction Based on Improved AHP and GPR

Ground penetrating radar (GPR) is widely used in advanced geological prediction. It is necessary to choose a scientific and effective evaluation method to give a reasonable evaluation of the accuracy of prediction. In this paper, a method based on improved analytic hierarchy process (AHP) and GPR is proposed to evaluate the accuracy of advanced geological prediction. Based on the analysis and induction of the factors that affect the accuracy of GPR prediction, an improved AHP is proposed, in which a new measure of “numerical weight” is added and the principle of maximum membership degree is integrated, and an improved AHP model is established for GPR prediction accuracy classification and evaluation. The engineering application of Xiaobeishan Tunnel of Jie-Hui Highway is taken as a case study, and it is proved that the evaluation indices are easy to obtain and the evaluation results are accurate and reliable. The improved AHP-GPR method can be further used for other tunnel engineering.

Advanced Geological Prediction Technology Based on Tunnel Face Borehole Drilling

In the process of drilling, the drilling tool contacts with the rock and soil directly. The response information of the drilling tool reflects the mechanical properties of the rock and soil comprehensively. A large amount of geological data hidden in the response information of the drilling tool can be used to analyze and determine the mechanical parameters and spatial distribution of the rock and soil, thus providing an important reference index for the identification of the formation interface and the classification of the surrounding rock. At present, the response information of drilling tools in the field of geotechnical engineering has not been collected, resulting in a great waste of data resources. To make full use of the relevant parameter information in tunnel blasthole drilling, the relationship between the parameters and the quality of surrounding rock is collected and established, and in combination with the geological situation of the face, the level of surrounding rock in front of the face is predicted. The tunnel of Sandu high-speed rail in Guizhou Province is used to conduct research on advance geological prediction technology based on borehole drilling of tunnel face, and the following results are obtained. The drillability of rock is directly related to drilling speed V, vibration acceleration a, and vibration frequency f. Theoretical research on short-distance geological prediction of borehole drilling in tunnel face is completed on this basis. A set of while-drilling monitoring equipment is developed and applied to pneumatic rock drill. While-drilling equipment can collect the real-time data of drilling speed V and vibration acceleration a of the drilling machine. The data is collected based on the analysis of drilling rate V and vibration acceleration a. The quantitative relationship between rock mass level and drilling information is established. Through application in supporting engineering, a standard database of rock antidrilling coefficient of different levels of surrounding rock based on the rock type of quartz sandstone is preliminarily established. This database is better than the geological report of the excavation site.

Research of Advanced Geological Prediction in Tunnel Excavation with Ultra-long Broken Zone

The advanced geological prediction is carried out by using ground penetrating radar, infrared water exploration and seismic reflection method (TSP) for the shallow fractured zone of Laoyingshan tunnel. The prediction accuracy is over 95%. It is suggested that the advanced prediction method can be used in the follow-up similar tunnel projects to improve the information level of tunnel construction and ensure the quality and safety of the project.

Advanced geological prediction technology of tunnel based on image recognition

The purpose of this study is to solve the problem that the image obtained by the advanced geological prediction technology of tunnel in the tunnel engineering construction project is difficult to identify, the identification result of the original image is too dependent on the personal habits and experience of the forecaster, and the identification result is not accurate enough. In this study, the geological radar image is taken as the research object, and the method of the advanced geological prediction technology of the tunnel is studied and summarized. The image pattern recognition technology is introduced into the advanced geological prediction of the tunnel, and the image recognition of the geological radar image is carried out. After preprocessing of filtering, binarization, and refinement, it is found that the image can be more accurate, and the impact of noise on the image is also alleviated. In addition, neural network pattern recognition technology is adopted after image preprocessing to establish a neural network model. After recognition, curve targets can be successfully detected, indicating the feasibility of image recognition technology. Therefore, the image recognition technology can make up for the deficiency of the observation personnel’s understanding of the geological radar image due to personal habits, and it provides a new way to identify the advanced geological prediction technology of the tunnel.

Development Status of Digital Detection Technology for Unfavorable Geological Structure of Submarine Tunnel

Gao, X.-C.; Ba, X.-Z.; Cui, E.-Y.; Wang, J.; Zhang, T.-T.; Sun, S.-Q., and Hou, W., 2019. Development status of digital detection technology for unfavorable geological structure of submarine tunnel. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 306–310. Coconut Creek (Florida), ISSN 0749-0208.The detection of unfavorable geological structures in tunnels is a major theoretical and technical problem in the tunnel construction process. There are many kinds of geological disaster sources for submarine tunnels, and there is currently no effective technology and method to detect them. This paper summarizes the, status of research on disaster source prevention and control based on the advanced geological prediction for submarine tunnels and laser-point cloud imaging technology from two aspects - the exposed structural plane and the internal rock mass structure. In the investigation on submarine tunnel structural planes, digital compass contact measurement, close-range photogrammetry and laser scanning have become important means to support the development of geological surveys on submarine tunnel structural planes, and a three-dimensional rock mass structure information integration analysis method has also been initially formed based on structural plane network simulation. In the detection and control of submarine tunnel structures, an effective submarine tunnel disaster source detection and control system has been formed. Combined with the research work of the team, this paper systematically expounds the development status of the digital detection technology for unfavorable geological structures in the existing tunnels, and the research results can provide some references for the research in this field.

TBM in Azad Kashmir region of Pakistan: in situ stress measurements for rockburst prevision

Using the authors’ experience, this paper details the in situ stress measurements in twin tunnel boring machine (TBM) tunnels of the Neelum Jhelum hydropower project, located in the Azad Kashmir region of north-east Pakistan in foothills of the Himalayas, with overburdens up to 2000 m and high tectonic stresses in very complex geology. The ability to predict the likelihood, location, severity and number of rockbursts directly impacts on the tunnel safety and daily production rates. This, combined with the lack of previous project experience in similar conditions, has required the use of all the available advanced geological prediction methods: forward probing, tunnel seismic tomography, continuous microseismic monitoring and in situ stress measurements were used. These methods, except in situ stress measurements, only gave an indication of likelihood and severity of rockbursts. The in situ tests provided the actual ground stresses and their orientations. The in situ stress results contradicted the forecasts based on the classical empirical rules combining stress analysis and rock strength. This paper is focused on the in situ stress measurements carried out behind the two TBMs and details the information obtained and how data were interpreted and integrated to support excavation, prevention and control of rockbursts, which improved tunnel safety and productivity.

Research on Advanced Tunnel Geological Detection and Prediction Technology Based on Three-dimensional Dynamic Point Source Induced Polarization Method

This paper introduces the basic principle of the comprehensive geological prediction method of tunnel, and summarizes the key points and key points of the comprehensive geological prediction method of tunnel in the construction of highspeed railway tunnel. The comprehensive geological prediction method and tunneling effect are compared. The results show that the comprehensive geological prediction method is effective and accurate. At last, this paper expounds the problems existing in the advanced geological prediction of high-speed railway tunnel, and puts forward the corresponding solutions.

Application of comprehensive prediction method of water inrush hazards induced by unfavourable geological body in high risk karst tunnel: a case study

ABSTRACTWhile tunnelling in karst terrains, karst fissure water may endanger the safety of tunnel engineering and cause geological disasters such as water inrush. To ensure the safety of tunnel construction, in investigation stage, engineering geological and hydrogeological conditions of Jigongling Tunnel was analysed firstly. In design stage, a reasonable prediction method combining with optimization principle was selected to calculate the water inflow according to the geological and hydrogeological conditions analysed in the investigation stage. Then the advanced geological prediction was divided into different classes based on the water inflow. To make an accurate prediction, tunnel seismic prediction method, transient electromagnetic method, induced polarization method and advanced geological drilling were comprehensively applied in construction stage. This method combined with geology analysis, water inflow calculation and classification of advanced geological prediction is successfully applied in the Jigongling Tunnel of Fanba Expressway, and has provided a reference for the similar engineering constructions.

Analytical model for assessing collapse risk during mountain tunnel construction

Risk management for safety in mountain tunnel construction is of great significance. However, existing research lags behind engineering applications. In this paper, the risk of mountain tunnel collapse is used as an example to illustrate a new assessment method based on case-based reasoning, advanced geological prediction, and rough set theory. First, the risk surroundings and risk factors involved in tunnel collapse are integrated and summarized, and a risk assessment index system is established for tunnel collapse. At the same time, because the dynamic response parameters obtained by the advanced geological prediction usually indicate a typical geological structure, sensitive response parameters are introduced in the assessment index system. Advanced risk assessment can be performed for tunnel sections at a certain distance ahead of the tunnel face. Second, the major risk surroundings and the advanced geological prediction results are analyzed for the tunnel under assessment. Cases with similar attribute characteristics are selected via comparison with previous cases. Attribute reduction and calculation of weights are subsequently performed for the risk surroundings and risk factors of similar cases based on the attribute significance theory of rough sets. Finally, index screening and objective weights are applied in the fuzzy comprehensive assessment model. The results of this paper can be used to improve the theoretical level and reliability of risk assessment in tunnel safety and serve as a reference for tunnel construction.

The Application of Tunnel Reflection Tomography in Tunnel Geological Advanced Prediction Based on Regression Analysis

In the tunnel construction, due to the limitation of the survey and design and the complex dynamics of tunnel surrounding rock geological conditions, so it is difficult for complex geology with the microscopic accurate grasp, often which caused by geological exploration data do not tally with the actual situation, often encountered in karst water inrush, large deformation in weak rock, cave-in subsidence, geological hazards, such as gas outburst, rock burst cause person casualties, delays, in order to minimize geological disaster influence degree, advanced geological prediction before construction is very necessary. Using regression analysis, based on engineering vault subsidence and horizontal convergence has carried on the regression analysis, research results can be reference for related engineering design and construction. Detailed introduces the principle, methods and outstanding characteristic of tunnel reflection tomography advanced prediction system, and take Jianfengling mountain tunnel of Darui line railway as an example, the prediction results are analyzed in detailed processing, and on-site validation, finally points out the problem for further study the technology.

Application of Tunnel Seismic Image Approach to the Advanced Geological Prediction for Tunnel

With the large-scale construction and rapid development of underground engineering, a large number of underground engineering construction, such as tunnel and subway emerged. The geological structure of the tunnel is complex and the roc is fragmented. Tunnel seismic image is a new geophysical technique. This method has advantages such as high resolution, high reliability and obvious image characteristics. Therefore, to insure the safety of the construction and to eliminate geological disasters, the advanced prediction technology of seismic image in tunnel detection is applied. In the paper, the seismic image was used to detect the Huangzhuang tunnel geological condition. The reflected waves, the refraction wave and the surface waves can reflect the same geological conditions, and the result is in accordance with the drilling. Tunnel seismic image can effectively and safely guide the excavation of the tunnel section working surface in combination with reconstructed images and excavation technology.

Risk assessment of water inrush in karst tunnels and software development

Water inrush makes time extended, instruments destructed, and casualty increased, which is the biggest threat for safe construction of tunnels in karst areas. A software system for risk assessment of water inrush was established with considering eight risk factors, including groundwater level, unfavorable geology, formation lithology, topography, strata inclination, excavation, advanced geological prediction, and monitoring. In the present software system, fuzzy mathematics and Analytical Hierarchy Process (AHP) were used to quantitatively describe the risk levels for each factor. The influence degree of each factor to water inrush was assigned an objective weight and a subjective weight, and the proportion of the two weights in the risk assessment was defined as weight distribution. The objective weights of the risk factors were obtained from more than 100 water inrush instances in karst tunnels, whereas the weight distribution was totally derived from expert field assessment and subjective weights were determined by using AHP in the risk assessment. Two case studies of karst tunnels were applied to check the reliability of the proposed software system, and the comparisons between the software assessment and practical excavation yield good consistency. Therefore, the software system can appropriately be used in practice to forecast water inrush in karst tunnels.