Tunnel Roof Research Articles

Analysis and Research on Energy Consumption of a Non-Contact High-Efficiency Tunnel De-Icing Device

In this paper, a laser deicing device for tunnel is designed to solve the inconvenience of deicing the tunnel roof wall. First of all, Solidworks software was used to create a 3D model of the laser deicing device, namely the track module, the base platform, and the work platform. Then, ANSYS simulation software is used to simulate the process of laser deicing. When the initial temperature of icicle is -5℃, -10℃, -15℃ and -20℃, the distance between laser and icicle is 1.5m, 2m, 2.5m and 3m, and the wind speed is 2m/s, 3m/s, 4m/s and 5m/s, respectively. The depth of 200s of laser irradiation and the time of full penetration were simulated under three variables. It is concluded that the higher the initial temperature, the closer the distance and the smaller the wind speed, the lower the deicing energy consumption. Finally, the experiment results are consistent with the simulation results, which further verifies the accuracy of the simulation. The laser deicing detection device studied in this paper provides a certain theoretical basis and reference value for the application and development of intelligent deicing equipment in tunnels.

Investigations of sequential excavation and reinforcement in tunnels based on the extended three-dimensional discontinuous deformation analysis method

The unloading effect of excavation is the key factor leading to rock mass instability, and bolt support is the key means of controlling the stability. However, the original three-dimensional discontinuous deformation analysis method (3D DDA) can only simulate rock mass instability and bolt support after the tunnel is excavated, which makes it difficult to study the effect of tunnel excavation and bolt support on rock mass stability. Therefore, an algorithm to confirm the excavated blocks and reinforced blocks based on the volume judgment method (VJM) was proposed in this paper. Sequential excavation and reinforcement in tunnels can be simulated by introducing the time variables of block excavation and bolt deployment into the 3D DDA method. By embedding these two algorithms in the 3D DDA method, an extended 3D DDA method for sequential excavation and reinforcement in tunnels was developed, named the 3D DDA_ES method. Based on the 3D DDA_ES method, the collapse that occurred during the construction of the Huangjiazhuang Tunnel was simulated, and the displacement of key blocks and the axial force of the bolts were analyzed. According to the simulation results, the axial force on the bolts is strongly related to the position of the key blocks, and the axial force on the bolts at the tunnel roof is much greater than that at the tunnel arch shoulder. In this regard, these bolts with axial forces less than 1 kN are removed during the simulation, and the key blocks remain stable with a maximum displacement of 12 cm. The research results can provide a theoretical basis for tunnel construction and reinforcement parameter optimization for similar projects.

Roof stability analysis for a shallow-buried cylindrical tunnel in Hoek-Brown rock strata

Roof stability of shallow-buried cylindrical tunnels in rock strata following the generalized Hoek-Brown criterion (GHB) is analyzed in this work. Based on the limit analysis method, a three-dimensional (3D) shallow-buried collapse mechanism for tunnel roofs is developed to derive various stability measures. Optimization codes are programmed to capture the optimal stability measure solutions. The effects of the 3D geometric characteristics, the rock mass strength parameters, and the buried depth on tunnel roof stability are investigated by a parametric analysis. The critical buried depth ratios corresponding to the transition between the shallow-buried and deep-buried tunnel roof collapse mechanisms are also presented. Thereafter a series of stability charts of the required supporting pressure and the factor of safety (FoS) is proposed for design purposes. This study provides a theoretical basis for design and engineering of tunnels with limited buried depth.

High-Precision Drilling by Anchor-Drilling Robot Based on Hybrid Visual Servo Control in Coal Mine

Rock bolting is a commonly used method for stabilizing the surrounding rock in coal-mine roadways. It involves installing rock bolts after drilling, which penetrate unstable rock layers, binding loose rocks together, enhancing the stability of the surrounding rock, and controlling its deformation. Although recent progress in drilling and anchoring equipment has significantly enhanced the efficiency of roof support in coal mines and improved safety measures, how to deal with drilling rigs’ misalignment with the through-hole center remains a big issue, which may potentially compromise the quality of drilling and consequently affect the effectiveness of bolt support or even result in failure. To address this challenge, this article presents a robotic teleoperation system alongside a hybrid visual servo control strategy. Addressing the demand for high precision and efficiency in aligning the drilling rigs with the center of the drilling hole, a hybrid control strategy is introduced combining position-based and image-based visual servo control. The former facilitates an effective approach to the target area, while the latter ensures high-precision alignment with the center of the drilling hole. The robot teleoperation system employs the binocular vision measurement system to accurately determine the position and orientation of the drilling-hole center, which serves as the designated target position for the drilling rig. Leveraging the displacement and angle sensor information installed on each joint of the manipulator, the system utilizes the kinematic model of the manipulator to compute the spatial position of the end-effector. It dynamically adjusts the spatial pose of the end-effector in real time, aligning it with the target position relative to its current location. Additionally, it utilizes monocular vision information to fine-tune the movement speed and direction of the end-effector, ensuring rapid and precise alignment with the target drilling-hole center. Experimental results demonstrate that this method can control the maximum alignment error within 7 mm, significantly enhancing the alignment accuracy compared to manual control. Compared with the manual control method, the average error of this method is reduced by 41.2%, and the average duration is reduced by 4.3 s. This study paves a new path for high-precision drilling and anchoring of tunnel roofs, thereby improving the quality and efficiency of roof support while mitigating the challenges associated with significant errors and compromised safety during manual control processes.

Three‐dimensional stability analysis for a deep‐buried tunnel roof considering soil stratum strength nonlinearity

AbstractA three‐dimensional (3D) collapse mechanism was employed in this work to investigate the roof stability of deep‐buried cylindrical tunnels in soil considering strength nonlinearity. Based on the kinematic approach of limit analysis, three tunnel roof stability measures, namely, the stability number, the required support pressure, and the factor of safety solutions were derived to provide quantitative indicators for evaluating tunnel roof stability. Optimal upper bound solutions for these measures were obtained through optimization. Subsequently, the effects of soil strength nonlinearity and 3D geometry characteristics on roof stability and the profiles of collapsing blocks were investigated: The increase in the nonlinear coefficient m and the tensile strength σt, as well as the decrease in the initial cohesion c0, will lead to a deterioration in the stability of the tunnel roof, and also result in a larger range of collapse blocks of the tunnel roof. A 3D stability analysis of the tunnel roof can provide more reasonable stability estimates than a 2D stability analysis. When the length‐to‐radius ratio L/R → ∞, the 2D solution results.

The anatomical variations of the cubital tunnel in a South African body donor sample

PurposeThe ulnar nerve (UN) courses through the cubital tunnel, which is a potential site of entrapment. Anatomical variations of the cubital tunnel may contribute towards cubital tunnel syndrome (CuTS), however, these are not well described. The aim was to compare the range of variations and dimensions of the cubital tunnel and the UN between sexes and sides of the body.MethodsSixty elbows from 30 embalmed bodies (17 males and 13 females) were dissected. The prevalence of the cubital tunnel retinaculum (CuTR) or anconeus epitrochlearis (AE) forming the roof of the tunnel was determined. The length, width, thickness, and diameter of the cubital tunnel and its roof were measured. The diameter of the UN was measured.ResultsThe AE was present in 5%, whereas the CuTR was present in the remaining 95% of elbows. The tunnel was 32.1 ± 4.8 mm long, 23.4 ± 14.2 mm wide, 0.18 ± (0.22–0.14) mm thick, and the median diameter was 7.9 ± (9.0–7.1) mm, while the median diameter of the UN was 1.6 ± (1.8–1.3) mm. The AE was thicker than the CuTR (p < 0.001) and the UN was larger in elbows with the AE present (p = 0.002). The tunnel was longer in males (p < 0.001) and wider on the right (p = 0.014).ConclusionThe roof of the cubital tunnel was more frequently composed of the CuTR. The cubital tunnel varied in size between sexes and sides. Future research should investigate the effect of the variations in patients with CuTS.

Optimization of inclined coal seam tunnel section angle and anchor angle based on response surface method

The mining of inclined coal seams is often accompanied by problems such as difficult to control deformation of the tunnel roof and failure of anchor bolts. Taking the transportation channel of Jinping Coal Industry 1071-1 in Shanxi Xiangkuang Mine as the background, FLAC3D numerical simulation software was used, and the method of response surface experimental design and data analysis was used to systematically study the effects of the anchor installation angle and the roof inclination angle of the tunnel section on different inclination angles. Influence of the surrounding rock stability of coal seam roadways. On this basis, a multi-index tunnel support design evaluation method based on the response surface method was proposed, and the actual support plan was optimized and industrial tests were carried out based on the actual on-site support plan. The research results show that: in terms of inclined coal seam support, the degree of influence on the tunnel stability is in the following order: anchor installation angle &gt; tunnel section roof inclination angle &gt; coal seam inclination angle; the optimized support design obtained through the proposed technology The method has good application effect and can improve the stability of the roadway during the mining of the working face. It also proves the effectiveness of this technology and provides new ideas for the design of anchor support of inclined coal seam roadways and the optimization of roadway sections.

Analysis of the quality of tunnel roof topography by automatic cutting control under the coupling of multiple factors.

The automatic cutting of coal and rock surface morphology modeling based on the actual geological environment of coal mine underground excavation and mining is of great significance for improving the surface quality of coal and rock after cutting and enhancing the safety and stability of advanced support. To this end, using the principle of coordinate transformation, the kinematic trajectory of the cutting head of the tunneling machine is established, and the contour morphology of the cutting head under variable cutting technology is obtained. Then, based on the regenerative vibration theory of the cutting head, a dynamic model of the cutting head coal wall is established, and the coordinate relationship of the cutting head in the tunnel coordinate system under vibration induction is analyzed. Based on fractal theory and Z-MAP method, a simulation method for the surface morphology of coal and rock after cutting is proposed, which is driven by the cutting trajectory Under the coupling effect of cutting vibration induction and random fragmentation of coal and rock, simulation of the surface morphology of comprehensive excavation tunnels was conducted, and relevant experiments were conducted to verify the results. A 1:3 similarity experimental model of EBZ160 tunneling machine was used to build a cutting head coal and rock system cutting experimental platform for comparative experiments of cutting morphology. Furthermore, statistical methods were used to compare and evaluate the simulated roof with the actual roof. The results show that the relative errors between the maximum range of peaks and valleys, the peak skewness coefficient of height standard deviation, and the kurtosis coefficient of the actual roof are 1.3%, 24.5%, 16%, and 2.9%, respectively. Overall, this indicates that the surface morphology distribution characteristics of the simulated roof and the actual roof are similar, verifying the effectiveness of the modeling and simulation method proposed in this paper, and providing theoretical support for the design and optimization of advanced support in the future.

Stability analysis of three-dimensional tunnel roofs in soil based on a modified MC criterion

Stability analysis of three-dimensional tunnel roofs in soil based on a modified MC criterion

Prediction and optimization of adverse responses for a highway tunnel after blasting excavation using a novel hybrid multi-objective intelligent model

It is one of the main challenges of modern traffic engineering to monitor and control the adverse response of highway tunnels after blasting excavation. To that end, this paper proposes a novel hybrid multi-objective intelligent model to predict and optimize four adverse responses including tunnel roof settlement (TRS), linear overbreak (LO), underbreak area (UA), and the maximum block size (MBS) based on a case highway tunnel. This model is assembled by the support vector regression (SVR) and a multi-objective golden jackal optimization (MOGJO) algorithm. 95 monitored data after tunnel blasting containing 11 features of four categories are used to train and test the models. Other five classical intelligence models are also developed to compare the predictive performance of the proposed model. The results of model development indicate that the proposed model has the optimal predictive performance among all models when the ratio of training set to test set is 8: 2. The calculation results of performance evaluation indices (determination coefficient (R2) and root mean square error (RMSE)) demonstrate that the proposed MOGJO-SVR model is the best model for predicting four tunnel adverse responses among all models, i.e., TRS (R2: 0.9837; RMSE: 0.5591), LO (R2: 0.9711; RMSE: 4.5022), UA (R2: 0.9800; RMSE: 0.3803), and MBS (R2: 0.9535; RMSE: 5.9248). Besides, the model interpretation results based on the Shapley additive explanations (SHAP) method show that the contribution of blasting and explosive parameters to the adverse responses is significant. Then, a visualization procedure is generated to optimize the adverse responses for different tunnel excavation designs in real time. This work guides the prediction and control of adverse responses in highway tunnel construction.

Seismic performance of soft rock tunnel under composite support conditions

In order to effectively improve the seismic and impact resistance performance of soft rock tunnels, a composite support method was proposed and validated in the paper. The UDEC (Universal Distinct Element Code) model of soft rock layers was established, and the movement and subsidence characteristics of the roof and floor of the rock layers under impact loads was simulated and calculated. As a result, a composite support scheme with good cushioning performance was proposed. The top and sides of the tunnel were supported by a combination of anchor rods of different lengths and metal mesh, reinforced by steel beams and vibration absorbing filler around. The anchor rod was designed as a segmented loading structure, and can be set to different preloading forces based on the internal deformation of the rock layer. The dynamic response testing scheme was designed, and the results indicate that the segmented loading anchor rod has a significant buffering effect on the response to impact load, and can provide reasonable tension feedback at different stages. Research has found that when the water cement ratio is 0.5-1.5, the curing efficiency and strength are both higher. In order to compare the seismic performance of composite support and traditional constant resistance anchor rod support, local blasting experiments were conducted. Based on a blasting vibration tester, a data detection and transmission system were designed to obtain the vibration speed of the tunnel roof during the vibration process. The research results show that composite support can reduce the maximum vibration by more than 40 %, stabilize the fragmentation coefficient at 1.38, and have a very significant vibration reduction effect.

The prevalence of the anconeus epitrochlearis muscle in a Central European population.

An anconeus epitrochlearis muscle (AE) is a common anatomical variant in the upper extremity, located at the medial aspect of the elbow. Its anatomical position contributes to the roof of the cubital tunnel. While it plays a role in protecting the ulnar nerve, it may also pose a risk for ulnar nerve compression. This study aimed to determine the true prevalence of AE in a Central European population. The presence of AE was evaluated in 115 cadaveric upper extremities from an undetermined number of subjects. The limbs for dissection were assumed to be healthy, and AE identification involved anatomical description and measurements. Data analysis aimed to determine the true prevalence, considering 95% confidence intervals. AE was present in 5 of the 115 cadaveric limbs (4.3%). Specimens lacking AE were observed, depicting normal cubital tunnel roof anatomy. When present, AE replaced the proximal part of the cubital tunnel roof, superficially coursing to the ulnar nerve. Morphological variations were noted. The true prevalence of AE was 4.3% (95% CI = 0.2%-8.4%), consistent with recent studies. Historical reports indicate varying true prevalence up to 26%, possibly linked to manual labor changes. Contrary to prior assumptions, our study did not find a significantly higher true prevalence in the European population. AE's association with cubital tunnel syndrome is complex, with both protective and potentially compressive roles.

On the dynamic stability of tunnel roof in nonuniform rock/soils characterized by nonlinear Mohr envelope

This study proposes a pseudo-static procedure for investigating roof stability of deep-buried tunnels in non-uniform rock/soil surrounds, on the basis of a generalized nonlinear Mohr envelope and upper bound theorem. Non-uniformity of rock/soil surrounds is discretized to certain layers characterized by differing rock/soil properties. An effective collapse mechanism is constructed, satisfying an associated flow rule and the generalized Mohr envelope. After having computed the internal and external rates of work, the upper bound formulations including collapse profile, collapse height and width are derived based on work rate balance equation. FE modelling is simulated to verify the analytical solutions with and without considerations of vertical dynamic forces. Effects of corresponding parameters representing rock/soil properties and external forces are investigated to demonstrate the implication on tunnel roof stability, aiding to provide reference for design and engineering practice.

A possible underground roadway for transportation facilities in Kathmandu Valley: A racking deformation of underground rectangular structures

AbstractThe increasing number of private cars, public transportation vehicles, and pedestrians, as well as the absence of adequate space for these ground amenities, are one of the primary causes of traffic congestion and accidents in the Kathmandu Valley. Investigations have indicated that the Kathmandu Valley has the greatest traffic accidents despite the heavy presence of the government and its agencies there. Most teens and young adults suffer injuries while using motor vehicles. The study's primary objective is to foresee and prevent such complications by planning for sufficient subsurface infrastructure (a cut‐and‐cover rectangular tunnel) for the Kathmandu Valley's transportation network. The overlying pressure, lateral earth pressure, live load, uplift pressure, and live surcharge are some of the forces acting on the tunnel, creating unique stress and moment zones. The tunnel meets the following geometric requirements: (a) Each of the tunnel's two cells has a clear span of 10 m and a clear height of 5.5 m. The side walls, inner walls, top slab, and bottom slab are all 700 mm thick. Soil has built up to a height of 4 m over the tunnel's roof. The analytical method is used in the tunnel segment's analysis. Furthermore, the designed tunnel has been evaluated for stability, considering the deflection and shear resistance. The analysis indicates that the tunnel meets the stability requirements. This implies that the structure is capable of withstanding the applied forces without excessive deflection. Non‐linear dynamic time history analyses of the El Centro earthquake and the Gorkha earthquake were computed. From the El Centro earthquake, the maximum displacement was 23.63 mm at 10.59 s, and from the Gorkha earthquake, the maximum displacement was 16 mm at 0.19 s for the modeled structures.

On smoke layer thickness in short naturally ventilated tunnels with arched roof

Understanding the characteristics of smoke layer thickness is vital for accurate fire detection, efficient smoke exhaust and safe evacuation in tunnel fire. Nevertheless, smoke flow in tunnels with arched ceiling may show different characteristics from the tunnels with flat roof which is usually studied. Theoretical analysis was conducted on the smoke flow characteristics and thickness under the curved roof of natural ventilation tunnel, and further, numerical simulations were performed to elucidate and verify the mechanism. The results show that smoke mass flow rate is positively correlated with heat release rate(HRR) and section radius. However, the smoke layer thickness is not significantly affected by HRR, and is positively related to the section radius. Based on the mass conservation, a practical prediction model for smoke layer thickness under arched ceiling was derived, and an empirical equation for estimating the total smoke mass flow rate was also proposed. The results presented fairly good agreement with simulations and experimental data from previous works.

Karangkates Railway Tunnel Risk Analysis Based on Ground Penetrating Radar Data

The Karangkates railway tunnel in Malang Regency is more than half a century old and has undergone land use changes into settlements and highways. This study aims to identify cavities between the ground surface and the roof of the Karangkates tunnel using Ground Penetrating Radar (GPR) data. Primary data were obtained through GPR measurements and interviews with residents. Qualitative methods are used to analyze GPR interpretation data readings and risk analysis. Risk analysis is carried out to determine the location and area of cavities and compile long-term risk management. From the results of the GPR analysis, 6 points were found with protruding cavities, with a cavity depth between 8 to 13.4 meters. The location of such cavities is in residential areas and highways. Risk management measures appropriate to the analysis and observation of the research site are carried out to reduce the impact of risk. The results showed that the risk value was low. By implication, appropriate corrective and maintenance actions must be taken to mitigate risks and maintain public safety.

Construction practice of water conveyance tunnel among complex geotechnical conditions: a case study

The construction practice of water conveyance tunnels often encounters various complex geotechnical engineering conditions, which bring huge challenges to the design and construction of water conveyance tunnels. Based on the theory of rock elastic–plastic mechanics and finite element analysis technology, this article carried out investigations of engineering geological features, geological formations and hydrological conditions establishes a calculation model for the 3# water conveyance tunnel of the Fenhe River Diversion Project, and analyzes the variation law of surrounding rock stress and displacement during TBM excavation of the tunnel. The results indicate that the dominant direction of the rock mass principal stress measured by the hydraulic fracturing method is NE84°, and the maximum horizontal principal stress, minimum horizontal principal stress, and vertical stress decrease sequentially, analyzing the characteristics of shield TBM construction technology, it is applied to the construction of water transfer tunnels. The numerical simulation of TBM construction using FLAC3D software shows that as the excavation surface advances, the subsidence value of the tunnel roof first slowly increases, then rapidly increases, and then tends to stabilize. The horizontal displacement of the surrounding rock is increasing. The maximum principal stress of the surrounding rock gradually increases. The final surrounding rock stress is 35 MPa. The TBM shield machine with mud water balance driven by indirectly controlled frequency conversion motor is selected for TBM construction of the tunnel. The study offers statistical information to support tunneling technology for water conveyance in the geotechnical engineering practice.

The influence of a combined aerator on aeration characteristics

Aerators with sharp lateral enlargements and bottom drops generally cause adverse effects in spillway tunnels with a mild base slope, including serious cavity back flow and water wings striking the tunnel roof. Taking RM Hydropower Station’s spillway tunnel as its example, this paper proposes a new type of combined aerator characterized by a “variable base slope” longitudinally and a transverse “sharp enlargement plus straight section.” This not only increases cavity stability, resulting in more effective aeration, but also inhibits the development of water wings, contributing to an improved pattern of water flow. In addition, this paper systematically explores the influence of the flip bucket (drop), gently sloping section, and steeply sloping section of the “variable base slope” aerator upon the aerated cavity and summarizes the rules according to which the sharp lateral enlargement and diffusion angle influence the formation of water wings. This offers technical solutions, with theoretical support, for the design of aerators in spillway tunnels with a mild base slope.

Complementation of analytical solutions for the quantitative roof stability analysis of rock cavities and tunnels

This study revisited a well-founded analytical solution describing the collapse profiles of tunnel roofs and estimated traditional stability measures to be used for quantitative safety assessment and practical engineering design. The original analytical approach was proposed by Fraldi and Guarracino based on a variational approach in the context of limit analysis, and subsequently extended to account for pore-pressure, seismic excitation, shallow buried depth, and axis-symmetric analysis, etc. In this study, the optimal bounds for the stability number, shear strength-based factor of safety, and support pressure were derived from the available original and extended analytical expressions of the failed block in both rectangular and circular tunnels. The computational results were in good agreement with those obtained with semi-analytical and numerical approaches but were obtained with much less computational effort. Regarding the tunnel at a shallow depth, a revised profile function was suggested by employing a different boundary condition that allowed the geometric restriction in the previous study to be eliminated; as a result, improved solutions could be obtained. All computation outcomes, including those of the extensions, were validated with those based on the piecewise linear failure mechanisms. The obtained failure mechanisms demonstrated an identical shape of the profile function in terms of curvature, and differences in safety measures were attributed to the dimension of the failed blocks. The proposed techniques in this study enrich the existing theoretical method while retaining its extreme simplicity.

Characterizing the bending behavior of underground utility tunnel roofs in a fabricated composite shell system

The traditional underground utility tunnel system is characterized by a lengthy construction period, material waste, and poor engineering quality. This study proposes the prefabricated composite shell system underground utility tunnel as a new type of prefabricated underground utility tunnel system. This system uses 20 mm thick high-performance cement-based materials as permanent templates, with steel reinforcement skeletons placed in the cavity between the two side molds, and concrete can be poured after on-site hoisting and positioning to form an integrated tunnel. This study first systematically introduces the system design method of the prefabricated composite shell system underground utility tunnel and clarifies its component and connection structures. Then, bending tests are conducted on the composite shell tunnel top plate specimens, and a cast-in-place top plate specimen is selected as a control group. A suitable bearing capacity calculation formula for composite shell top plates is derived and proposed based on test phenomena and results analysis. The results showed that the prefabricated outer template and internal cast-in-place concrete of the composite shell top plate specimen have good collaborative performance. Its bearing capacity, stiffness, and failure phenomena are consistent with those of cast-in-place components, as are its mechanical properties. In addition, the proposed bearing capacity calculation formula for a composite shell top plates is highly accurate and can guide the design of such components.