Complex Stratum Research Articles

Collagen fiber arrangement in the normal bladder lamina propria and their potential impact on the pathological substaging of bladder cancer stage T1.

The lamina propria (LP) of the urinary bladder lies between the urothelial mucosa and the muscularis propria. This complex stratum is composed of extracellular matrix, several cell types, and collagen types I and III fibers. LP invasion by urothelial carcinoma (progression from stage Ta to T1) is a determinant of bladder cancer advancement. We attempted to characterize collagen fiber arrangement in the LP. This could enrich our understanding of this important layer and potentially provide clues for sub-staging of the T1 bladder cancer. A total of 24 Masson trichrome-stained images of normal bladder, including 12,530 collagen fibers were quantitatively analyzed using the Dragonfly software. The LP was divided according to fiber orientation into superficial LP (SLP, 15% of the thickness) and the deep LP (DLP, 85% of the thickness). Collagen fiber geometry analysis demonstrated that the SLP fibers are more parallel to the urothelium with an average angle of 260±230 compared to 400±260 in the DLP (p=3.4X10-144), more packed (average distance to the closest fiber of 0.61±0.67 compared to 0.66±0.77, p=0.0001), and their aspect ratio is considerably longer (average of 1.93±0.12 compared to 0.20±0.11, p=2.84x10-8). No difference was found in fiber perimeter or Feret diameter. Thus, we conclude that bladder collagen fibers are arranged in two distinct layers: a dense-ordered SLP and a loose disorder DLP. This indicates that the physical barrier to cancer cell invasion probably lies in the SLP, immediately underneath the urothelium. Once this barrier is breached, the looser and disorganized DLP poses no remarkable obstacle. Thus, we believe that histology-based subdivisions of stage T1 are expected to fail in providing clinically meaningful prognostic information.

GFNS: An OpenGL-based tool for shield tunneling simulation in 3D complex stratum

Shield tunneling under complex geological conditions may lead to uneven surface settlement, thereby posing risks of damaging adjacent structures. This paper introduces the Geological Model for Numerical Simulation (GFNS) software, which employs OpenGL to implement a 3D geological model. The software incorporates an advanced geological stratum meshing algorithm based on conditional statements, facilitating the swift construction of numerical models for shield tunneling in intricate geological formations. In this study, a numerical model for shield tunneling in complex geological conditions was developed using GFNS. The research investigated potential risk levels to adjacent structures due to shield tunneling through alternating soft and hard geological strata along the tunnel's longitudinal axis. Moreover, the influence of shield excavation position and construction parameters on surface settlement was analyzed. Finally, a comparison was conducted with the traditional parallel geological modeling approach. The results revealed that simulating shield tunneling while considering complex geological conditions demonstrates a stronger correlation with the laws of stratum settlement. Thus, GFNS offers an auxiliary modeling method for simulating shield tunneling under complex geological conditions.

Analysis of the seismic performance of a large underground station structure in complex stratum considering the influence of axial force

The large underground structure in saturated stratum is vulnerable to float during an earthquake. This results in a plethora of problems, such as uneven settlement, large internal force and structure damage. In this study, the seismic behavior of a three-story, two-span subway station in complex saturated stratum was investigated through water-soil fully coupled 3D finite element method. In the analysis, the nonlinear soil behavior was described by a cyclic mobility model and the structure was calculated using a nonlinear constitutive model which can consider the influence of axial force on its bending moment. Joints elements were used to model the contact surface between soil and structure. The development of the soil displacement and internal force of the station structure at different times during a huge earthquake was examined. The bearing capacity of the station structure members was analyzed. The results indicated that the vertical displacement was spatially distributed. The larger additional seismic stresses appeared in the bottom slab and side wall. Failed elements were observed in both the walls and slabs, and the walls were more easily damaged than the slab. The results provide useful reference for the large underground structure seismic design in the construction of urban underground space.

Study on the Analysis of Pile Foundation Deformation and Control Methods during the Excavation of Deep and Thick Sludge Pits

This study aims to apply performance-based safety-assessment methods to the monitoring and numerical simulation of excavation engineering projects in order to comprehensively enhance engineering risk management and decision support. In this paper, a deep excavation project in Hefei with thick silty clay layers was studied. The analysis included the surface settlement, the deformation of support structures, the vertical and horizontal displacements of pile tops, axial forces in steel braces, settlement, and the horizontal displacement of a gravity retaining wall on the south side of the excavation using field-monitoring data. A refined three-dimensional finite element model was established to further analyze the distribution of uplift displacement at the bottom of the excavation, horizontal displacement, and bending moments of piles based on simulation results. The research findings indicate that phased excavation can reduce the spatial extent of disturbance to the surrounding soil caused by excavation. Additionally, the closer the location to the excavation and the thicker the underlying silty clay layer, the faster the rate of settlement change and the greater the surface settlement. The spatial structure formed by steel braces and pile foundations effectively reduced the horizontal displacement of the engineering piles. The study’s use of field monitoring and finite element simulation provided valuable insights into the deformation of support structures and the response of the surrounding soil to excavation, confirming the rationality and applicability of the support structure in this paper. The proposed method can serve as a reference for similar complex stratum excavation design and construction. The performance-based safety assessment is introduced, and the monitoring data, numerical simulation results, and performance targets are comprehensively analyzed to provide a reliable scientific basis for engineering decision making.

Review on the Influence of Complex Stratum on the Drilling Trajectory of the Drilling Robot

A complex stratum formed due to the influence of internal and external dynamic geological processes will lead to extremely complex mining conditions in deep exploration and development of oil, gas, coal and other resources, processes mainly threatened by disasters such as coal and gas conflict, mine water inrush, and rock burst. Combined with formation identification and measurement while drilling technology, the drilling level of underground drilling robot in coal mines is constantly developing. In order to prevent coal mine accidents and achieve safe and efficient mining, efficient and accurate drilling is the key, and should be based on research on the influence of complex stratum on the drilling trajectory. In order to comprehensively and systematically summarize the research on the influence of a complex stratum on drilling tool mechanics, this paper describes the history and current situation of complex stratum exploration, measurement while drilling technology, borehole bending conditions, stress analysis of complex coal seams on drilling tools, formation force theory and method, and geosteering drilling technology. In addition, the research and application of directional drilling technology in gas control, water hazard prevention and geological anomaly detection are also discussed.

Study on the whole process application of advanced grouting pipe shed support under urban complex stratum conditions

The stability control of surrounding rock is always one of the important problems in tunnel construction. As a representative of tunnel pre-construction technology, advance grouting pipe roof support method is widely used in underground space engineering under various complex geological conditions, especially in strata with many fractured rock masses and rich groundwater content. Due to the complexity of the application of advance grouting pipe roof method, few studies have been conducted on the whole process of pipe roof application in actual projects. Taking the shield departure project of Guangzhou Metro Line 13 as the background, this paper uses the modified BQ method to grade the surrounding rock environment of the tunnel from the perspective of the stability evaluation of the surrounding rock of the tunnel. The result shows that the revised surrounding rock is grade v. further combining with the geological exploration report, it is found that the rock mass joints and fissures are large and may further develop under the change of the surrounding rock mass stress environment, and the formation water content is large. The surrounding rock is prone to large deformation under the action of groundwater, and even lead to surface collapse in serious cases. Therefore, it is necessary to adopt the advance grouting pipe roof support method. Subsequently, the influence of different pipe roof design parameters such as pipe roof diameter, number of pipe roofs, reinforcement thickness and layout range on its support effect is analyzed by using finite element software, and appropriate parameter values are determined and applied to the background project. Finally, considering the measurement error existing in actual monitoring, a dynamic safety evaluation method of tunnel structure based on reliability theory is proposed, and the background project is analyzed and evaluated by this method. The analysis shows that the tunnel structure with advance grouting pipe roof support meets the safety requirements, confirms the effectiveness of the design parameters, and can provide reference for tunnel construction under the same geological conditions.

The Face Stability Analysis of Shield Tunnels Subjected to Seepage Based on the Variational Principle

The stability of tunnel face remains a great challenge for tunnel engineers, especially when excavation is in a complex stratum under the water table. This paper aims to investigate the stability of soil in the front of a shield tunnel face induced by the presence of insufficient cabin pressure under the water table, on the basis of a variational principle and an upper bound theorem. The analytical expression of the rupture surface for the tunnel face is obtained, and the shapes of the rupture surface are plotted. Comparisons are made to check the present approach against the solution provided by numerical simulation techniques in order to show that the proposed method is valid. The parameter analysis indicates that the groundwater seepage has a significant effect on the range of the rupture surface for the shield tunnel face.

Frequency-Domain Full-Waveform Inversion Based on Tunnel Space Seismic Data

Tunnel seismic detection methods are effective for obtaining the geological structure around the tunnel face, which is critical for safe construction and disaster mitigation in tunnel engineering. However, there is often a lack of accuracy in the acquired geological information and physical properties ahead of the tunnel face in the current tunnel seismic detection methods. Thus, we apply a frequency-domain acoustic full-waveform inversion (FWI) method to obtain high-resolution results for the tunnel structure. We discuss the influence of the frequency group selection strategy and the tunnel observation system settings regarding the inversion results and determine the structural imaging and physical property parameter inversion of abnormal geological bodies ahead of the tunnel face. Based on the conventional strategies of frequency-domain acoustic FWI, we propose a frequency group selection strategy that combines a low-frequency selection covering the vertical wavenumber and a high-frequency selection of anti-aliasing. This strategy can effectively obtain the spatial structure and physical parameters of the geology ahead of the tunnel face and improve the inversion resolution. In addition, by linearly increasing the side length of the tunnel observation system, we share the influence of the length of the two sides of the observation systems of different tunnels on the inversion results. We determined that the inversion results are best when the side length is approximately five times the width of the tunnel face, and the influence of increasing the side observation length beyond this range on the inversion results can be ignored. Finally, based on this approach, we invert for the complex multi-stratum model, and an accurate structure and physical property parameters of the complex stratum ahead of the tunnel face are obtained, which verifies the feasibility of the proposed method.

Evaluation of segment convergence and settlement of subway shield tunnel in water-rich complex stratum

Based on the shield tunnel construction of the left line of Guowei road station-Qingshan lake west station of Nanchang metro line 3, the study focuses on the adverse effects of tunnel segment convergence and settlement deformation of vault and arch bottom on shield construction in the process of shield tunnel construction in water-rich complex stratum. The time-space curves of segment convergence and settlement value on typical monitoring sections are drawn, their variation laws are analyzed, and the deformation values of monitoring data are analyzed and tested. Based on the analysis results, the qualitative and quantitative evaluation of the overall or local deformation state of each monitoring object of tunnel segment is carried out. The results show that the cumulative deformation of each typical monitoring section is lower than the warning value, and the tunnel segment has a systematic offset in the horizontal and vertical directions of the clearance.

Analytical Model of Piezoresistivity for an Inner-Adhesive-Type Carbon Fibre Reinforced Plastic Tunnel Reinforcement.

Cracks in a tunnel lining often emerge under the coupling action of earth and water pressures in a complex stratum environment, and accidents often occur in the process of repairing cracks. In this study, we used the force-sensitive properties of embedded carbon fibre to conduct early-warning research on lining reinforcement to prevent secondary damage during tunnel lining reinforcement. According to the earth load characteristics, a bond stress–slip model of the embedded carbon fibre under bidirectional earth pressure was established on the basis of the thick-walled cylinder theory and the semi-inverse method in elastic theory. The length change of a single fibre was obtained on the basis of the principle that the volume of a single carbon fibre is constant during the deformation process. The resistance and strain model of the single carbon fibre under the action of an external force was then established following the relationship between the resistance, the length change and the volume change of the single carbon fibre. The resistance of carbon fibre composite materials, according to their production technology and unidirectional force properties, was assumed to be a mixture of the series and parallel resistances of the single carbon fibre, and a piezoresistive model of carbon fibre composite materials was formed by using the multidimensional Taylor series expansion and the idea of the average equivalent. The comparison between the theoretical and monitoring values of the piezoresistive model in a tunnel project in Tibet, China revealed that the resistance of various types of carbon fibres increases with the radius of the lining reinforcement and earth pressure and decreases with an increase in the lining reinforcement thickness. Meanwhile, the angles at different positions of the lining reinforcement also have certain effects on the resistance value of the carbon fibre. The variation curve of the piezoresistive model was exponential in both deeply and shallowly buried tunnels, which verifies the rationality of the model.

Seepage failure of a foundation pit with confined aquifer layers and its reconstruction

Seepage control is one of the key issues for the design and construction of deep soil excavation projects. A seepage failure occurred around an abandoned pile in a foundation pit with confined aquifer layers, and caused damages to the retaining wall and support system and surrounding environment. The causes of the accident are analyzed, and the reconstruction of the project are introduced. The seepage failure was attributed to the defects in the three-axis mixing piles and the potential weak region created around the abandoned pile. It was finally controlled by filling the whole foundation pit with water. A systematic reinforcement of the foundation pit was carried out. The soil disturbed by the seepage failure was reinforced by two-shot process grouting and sleeve valve pipe grouting. The cast-in-place piles and prestressed assembled steel struts were constructed to strengthen the original retaining wall and support system. An ultra-deep (61.5 m) trench-cutting re-mixing deep wall (TRD) was successfully constructed in complex stratum, and showed good waterproof performance through a pumping test. After the formal dewatering inside the foundation pit by three stages, the project was successfully finished. This study could provide a wealth of experience and guidance for the design and construction of future similar deep excavation projects.

Deformation and Control of Super-Large-Diameter Shield in the Upper-Soft and Lower-Hard Ground Crossing the Embankment

Compared with the small diameter and the single stratum shield tunnel, the surface subsidence is much greater when the large-diameter shield passes through the upper-soft and lower-hard stratum. In this case, it is particularly important to control the deformation of the embankment when the large-diameter shield passes underneath the embankment. Taking a tunnel project underneath the north embankment in Zhuhai as an engineering example, this paper investigates the deformation characteristics and safety control measures of a super-large-diameter (i.e., 15.80 m) shield tunnel underneath the embankment under complex stratum conditions in upper-soft and lower-hard strata, using on-site monitoring and three-dimensional numerical simulations. The results of the numerical simulation show that grouting can effectively reduce the settlement of the embankment. Grouting is applied to practical engineering, and the monitoring data are in agreement with the numerical simulation results. The surface subsidence of the embankment gradually increases as the shield tail leaves the monitoring section and finally stabilizes. After the shield machine has passed through the embankment, the horizontal deformation troughs on the embankment’s surface conform to the Gaussian normal distribution. The maximum settlement occurs in the area directly above the central axis of the tunnel. The deformation trough covers an area about four times the diameter of the tunnel on both sides of its center line.

Adaptive Vertical Positioning as Anti-Predator Behavior: The Case of a Prey Fish Cohabiting with Multiple Predatory Fish within Temperate Marine Algal Forests.

Simple SummaryFish cohabiting within structurally complex habitats (e.g., coral reefs, seagrass meadows, algal forests) include abundant small-bodied prey fish and specialized piscivorous fish. Habitat structural complexity mediating fish predator–prey interactions has been shown to be an important mechanism sustaining this coexistence. However, the effect of the vertical stratification of habitat structure on predator–prey interactions remains poorly known, especially within a forest-like marine habitat, i.e., a habitat containing three vertical strata (understory, canopy and open-water). We set up tank experiments to test how such habitat vertical stratification affects predator–prey lethal and behavioral interactions, using one prey and two predator model species cohabiting in Mediterranean algal forest. We found that prey anti-predator behavior was predator-specific. When exposed to a sit-and-wait predator, the prey increased its vertical distance from the predator, regardless of the habitat structure. Conversely, when exposed to a stalk-and-attack predator, the prey sought refuge within forest structures. Prey hide motionless within the canopy, the most complex strata, while they avoid and escape from predators within the understory, which is a less complex stratum allowing for fast prey movements but still protected from predators by the canopy above. Our results suggest the crucial role of habitat vertical stratification in influencing predator–prey interactions, which should be studied in three dimensions.Prey fish cohabit with specialized predator fish within structurally complex habitats. How the vertical stratification of the habitat affects lethal and behavioral predator–prey interactions and contributes to explaining these patterns has never been investigated within a forest-like marine habitat, i.e., a habitat containing three vertical strata (understory, canopy, open-water above). We studied this in tank experiments, with a model prey (the wrasse Symphodus ocellatus) and two model predators (the stalk-and-attack comber Serranus cabrilla and the sit-and-wait scorpionfish Scorpaena porcus), which are among the most abundant prey and predators cohabiting in Mediterranean Cystoseira forests. Wrasse anti-predator behavior was predator-specific. When exposed to the scorpionfish, the wrasse increased its vertical distance from the predator, regardless of the habitat structure. Conversely, when exposed to the comber, the wrasse sought refuge within forest structures: (1) the canopy provides more hiding opportunities due to its high complexity, and (2) the understory provides more escape/avoidance opportunities due to (a) its low complexity that allows for fast prey movements, and (b) the presence of the canopy above that limits the comber’s access to the understory. Our results suggest that habitat vertical stratification mediates predator–prey interactions and potentially promotes the co-existence of prey and multiple predators within marine forests.

Construction Technology of Connecting Passage in Complex Stratum with Large Buried Depth

Construction Technology of Connecting Passage in Complex Stratum with Large Buried Depth

Analysis of Corner Effect of Diaphragm Wall of Special-Shaped Foundation Pit in Complex Stratum

The number of special-shaped foundation pits is increasing fast because of the continuous utilization of underground spaces in urban areas. Based on the deep foundation pit of Maluan North Station of Xiamen Metro Line 2 in Xiamen, China, the deformation characteristics of the supporting structure of special-shaped foundation pits are researched by field observation and numerical simulation. Meanwhile, the depth of the concrete supports and steel supports is considered, respectively. The results show that the lateral deformation of the diaphragm wall at the corner of the pit shows obvious corner effect, and the maximum lateral displacement of the long-side diaphragm wall is slightly larger than the short-side diaphragm wall. Changing the position of the second layer of steel support has almost no effect on the lateral deformation of the corner diaphragm wall. Changing the position of the second layer of concrete support has a greater impact on the lateral displacement of the diaphragm wall, but the path of the maximum lateral displacement of the diaphragm wall and the depth of the point of maximum lateral displacement remain unchanged.

Numerical Simulation Study on Construction Effect of Top‐Down Construction Method of Suspended Diaphragm Wall for Deep and Large Foundation Pit in Complex Stratum

In order to study the deformation of a diaphragm wall and the settlement of surrounding soil under the complicated conditions of the deep and soft soil layer, which is underlying inclined rock and top‐down construction method, the construction scheme of suspended diaphragm wall based on the engineering practice of Oujiang North Estuary deep and large foundation pit of Wenzhou S2 railway is proposed, and the research method of numerical simulation is adopted in this article. By using Midas GTS finite element software, a three‐dimensional model of deep and large foundation pit excavation with top‐down construction method is established, and the internal force, deformation, and surface settlement of surrounding soil of suspended diaphragm wall with different depths into rock (1 m, 2 m, and 4 m) are analyzed. Furthermore, the optimization simulation research on the anchor locking scheme is carried out for the determined footed diaphragm wall. Similarly, the anchor locking scheme at a depth of 1 m into the interface between soil and rock is selected as the supporting scheme of the footed diaphragm wall through the simulation results. The research results of this article can guarantee the safety of diaphragm wall construction of deep and large foundation pit in complex stratum.

Research on Numerical Simulation of Top‐Down Construction Effect of Diaphragm Wall of Deep and Large Foundation Pit under Different Working Conditions in Complex Stratum

In order to study the construction effect of deep and large foundation pit excavation and its impact on the surrounding environment under complex stratum conditions, the deep and large foundation pit of the top‐down construction method of shield exit shaft of S2 line of Wenzhou City railway is taken as the research object in this paper. According to the complex geological conditions of deep soft soil layer with underlying inclined rock surface in Wenzhou, the numerical simulation method is used to carry out the related research. The simulation results of the deformation characteristics of the diaphragm wall under two different working conditions which are the same length diaphragm wall and the suspended foot diaphragm wall are compared and analyzed. According to the analysis results, the suspended foot diaphragm wall is determined as the final construction scheme of the diaphragm wall, and it is verified by field measurement. The research results can provide technical support for the construction of similar projects. At the same time, it can also provide basic accumulation for the construction of major projects in Wenzhou.

Research on Stratum Identification Method Based on TBM Tunneling Characteristic Parameters

In order to obtain continuous stratum information during TBM tunneling, using TBM tunneling parameters, stratum recognition is carried out through the K‐nearest neighbor model, and the model is improved by the entropy weight method to improve the stratum recognition rate. By analyzing the correlation between TBM tunneling characteristic parameters and stratum, the tunneling characteristic parameter vector which is most sensitive to the stratum is obtained by sensitivity analysis, and the stratum recognition model based on the K‐nearest neighbor algorithm is established. Aiming at the problem that the model has a large error in complex formation recognition, a formation recognition model based on the entropy weight K‐nearest neighbor algorithm is established, and the wrong data of the K‐nearest neighbor model is recalculated. The recognition rate of the stratum in the new model is increased from 90.95% to 98.55%. The results show that the K‐nearest neighbor model has a better recognition effect for the interval with single stratum distribution, and the recognition rate of entropy weight K‐nearest neighbor model for complex stratum is significantly improved, which provides an effective method to obtain stratum information by using tunneling characteristic parameters.

Study on the evaluation of adaptability of shield machine type selection in coastal complex stratum

The design and manufacture of the traditional shield machine not only does not strictly consider the various influencing factors of the shield tunneling but also directly selects the existing shield machine or carries on the adaptive transformation to the existing shield machine. According to the characteristics of shield tunneling construction, to solve the problem of blind selection of shield machines in the coastal complex stratum. First of all, an evaluation index system of shield type selection and adaptability considering the design parameters, hydrogeological conditions, and surrounding tunnel environments was established. After that, the fuzzy analytical hierarchy process (Fuzzy-AHP) is adopted to calculate the weight of different indices. However, it is difficult to pass the consistency test when calculating the weight of the analytical hierarchy process (AHP). An improved genetic algorithm (IGA) is introduced to make up for the weight calculation of AHP. Finally, based on summarizing various theories and experiences, the membership functions of each evaluation index are constructed according to the fuzzy theory, and the adaptive fuzzy comprehensive evaluation model of the selected type of the shield machine in the coastal complex stratum is proposed. A case study on shield machine selection of shield-driven tunnel works of the Xiamen Metro Line 4 Pengcuo North Station- Caicuo Station in China is introduced to illustrate the application of the proposed model. Moreover, the results provide a reliable basis for the selection and adaptability evaluation of shield machines in coastal complex formations.

Growth Kinetics of Bacillus pasteurii in Solid-Free Drilling Fluids.

A broken stratum is a complex stratum often encountered during drilling. Under erosion of the drilling fluid and disturbance of the drill pipe string, the rock in the well wall of the broken stratum is prone to collapsing and falling off, causing the well wall to lose its stability. Improving the cementing force between the broken blocks and forming a complete well wall are essential for overcoming this instability. The present study combined microbially induced calcite precipitation technology with solid-free drilling fluid technology for the first time to formulate a drilling fluid to overcome the instability of the well wall of a broken stratum. However, first and foremost, the growth of microorganisms in drilling fluids must be elucidated. To this end, experimental and theoretical analyses were performed to examine Bacillus pasteurii growth in drilling fluids composed of a single agent or combinations of various materials, such as a zwitterionic coating agent (FA367), a biopolymer (XC), a polyacrylate polymer (PAC-LV), and potassium polyacrylate (K-PAM). Experimental B. pasteurii growth data were then fitted using a modified Gompertz model. The mean square error indicated that the generated model had a reasonable degree of fit, and the bias and accuracy factors showed that the model could predict B. pasteurii growth. Among the different drilling fluid combinations used, suitable fluids for B. pasteurii growth were XC alone, XC, and PAC-LV in the two-material-based fluid and FA367, XC, and K-PAM in the three-material-based fluid. These results provide a solid foundation for the development of microbial drilling fluids to solve instability problems in broken geological formations.