Vertical Tension Research Articles

Characterizing large deformation of soft rock tunnel using microseismic monitoring and numerical simulation

Surrounding rock deterioration and large deformation have always been a significant difficulty in designing and constructing tunnels in soft rock. The key lies in real-time perception and quantitative assessment of the damaged area around the tunnel. An in situ microseismic (MS) monitoring system is established in the plateau soft tock tunnel. This technique facilitates spatiotemporal monitoring of the rock mass's fracturing expansion and squeezing deformation, which agree well with field convergence deformation results. The formation mechanisms of progressive failure evolution of soft rock tunnels were discussed and analyzed with MS data and numerical results. The results demonstrate that: (1) Localized stress concentration and layered rock result in significant asymmetry in micro-fractures propagation in the tunnel radial section. As excavation continues, the fracture extension area extends into the deep surrounding rockmass on the east side affected by the weak bedding; (2) Tunnel excavation and long-term deformation can induce tensile shear action on the rock mass, vertical tension fractures (account for 45%) exist in deep rockmass, which play a crucial role in controlling the macroscopic failure of surrounding rock; and (3) Based on the radiated MS energy, a three-dimensional model was created to visualize the damage zone of the tunnel surrounding rock. The model depicted varying degrees of damage, and three high damage zones were identified. Generally, the depth of high damage zone ranged from 4 m to 12 m. This study may be a valuable reference for the warning and controlling of large deformations in similar projects.

Effects of Staggered Plates on the Uplift Failure State and Bearing Capacity of NT-CEP Pile Groups

Plate position is an important parameter of a New Type Concrete Expanded-Plate (NT-CEP) pile. In this study, two small-scale test models and two, four, six, and nine finite element models were established using a visual small-scale model of half-section piles, an undisturbed soil pull-out test, and the ANSYS finite element software R19.0. The NT-CEP pile groups were studied with the plates set at staggered positions. This study mainly analyzes the displacement contours, stress curves, and load-displacement curves under the action of vertical tension and determines the influence of staggered plate positions on the performance and bearing capacity of the NT-CEP pile group, which provides theoretical support for its application in practical engineering. The bearing plate positions affect the performance of the pile group. The stress distribution in each pile in the pile group is uneven when plate positions are staggered, and the pile with the lower plate position bears a greater force. This has a great influence on the bearing capacity of the NT-CEP pile group. If allowed, the plates can be first set at the same position. If appropriate, the plates can be set in staggered positions; however, a reasonable distance between the upper and lower plates should be considered.

Influence of Plate Position on Uplift Failure State and Bearing Capacity of NT-CEP Pile Groups

The previous research results of the research group demonstrated that the plate position is the main factor affecting the uplift bearing capacity of the new type of concrete expanded plate pile (NT-CEP pile) group and the failure state of the soil around the pile. In this study, the visual half-section pile small-scale model of undisturbed soil tension test and ANSYS Finite Element Software comparative analysis two-pile small-scale test model and two-, four-, six-, and nine-pile models, which included the corner, side, and middle piles, were developed. The effect of the plate position on the displacement, stress, and bearing mechanism of the NT-CEP pile group under vertical tension was determined, which further improved the design concept of the NT-CEP pile group and provided strong theoretical support for its widespread application.

A unifying strut-and-tie model for conventionally reinforced link beams

Reinforced concrete link or coupling beams are usually cast integral with wall piers to help them act as a unit to resist lateral loads. The use of deep beam design in ACI 318-19 provisions leads to conservative shear designs for link beams which do not follow Euler-Bernoulli beams. Instead, strut-and-tie systems are used. The paper demonstrates the modeling of such beams using strut-and-tie provisions of ACI 318-19 Ch. 23. Alternatively, to using a time-consuming trial-and-error process, a unified general multi-panel strut-and-tie model is proposed, and simple design equations are developed to directly design conventionally reinforced link beams subjected to high shear force demand. As link beams have often a small span-to-depth ratio, the first one- and two-panel strut-and-tie models are considered basic and common. The one-panel model consists of a direct inclined compression concrete strut with horizontal tension ties in addition to the required crack-control web reinforcement and is used wherever the strut-tie angle is greater than the ACI minimum of 25 degrees; one vertical-to-two horizontal. The two-panel model is used when the beam span is too long to use the one-panel model and consists of one vertical tension tie and two steep inclined compression concrete struts. Worked design examples have been presented to justify and demonstrate the ease of implementation of the considered first two simple and direct models of the proposed unified general multi-panel strut-and-tie model. The predictions of the two basic models have been compared with five sample calculations and the comparison shows a good agreement.

2D stress rotation in the Tonga subduction region

Despite their enigmatic origins, deep earthquakes provide unique information about the stress distribution in slabs. Down-dip compression is expected at depth, due to resistance from endothermic phase transition near 660 km and increasing viscosity. Focal mechanisms for ordinary deep (620-680 km) earthquakes in the Tonga subduction zone exhibit down-dip compressional stresses in agreement with this expectation, but unusually deep (≥ 680 km) earthquakes exhibit vertical tension and horizontal compression. Here we present a numerical modelling study of the Tonga slab focused on stress patterns in the transition zone. The subducting Pacific plate is one of the oldest and thus coldest plates in the world, so our parametric study tests the effects of rheology and phase transitions on stress evolution for an exceptionally cold subducting plate. Our results suggest that direct buoyancy effects from the endothermic phase transition at 660 km depth are overprinted by bending-related forces. A stress pattern best fitting seismogenic stresses is found for the coldest tested subducting plate (150 Myr old) and a viscosity interface decoupled from the 660-km phase transition and shifted to 1000-km depth. An abrupt change of stress orientations is observed when the slab, temporarily deflected by the phase transition, penetrates to the shallow lower mantle and the fold of the flat-lying part is tightening.

An experimental and numerical study on the coupling effect of CLT wall-to-floor angle bracket connections

Cross-laminated timber (CLT) wall panels are commonly connected to the floor or foundation using metal connections, which play a critical role in determining the seismic performance and energy dissipation of the CLT shear walls. In this study, to comprehend the tension–shear coupling effect of the CLT wall-to-floor angle bracket connections under seismic loads, both monotonic and cyclic shear tests were conducted on the angle brackets that were also simultaneously applied with different levels of prescribed vertical axial tension. The influence of the co-existent axial tension on the horizontal shear performance of the angle brackets was analyzed. Furthermore, a numerical model of the angle brackets was developed and validated with the experimental results, which could predict the tension–shear coupling effect based on the monotonic loading scenario. Based on the numerical model, parametric analysis was conducted, and an analytical tension–shear interaction diagram representing the coupling effect of the angle brackets under seismic loads was established. It is found that with an increase of the axial tension from 0 to 30 kN, the shear resisting capacity of the angle brackets is diminished by 33.29%, and the pinching effect of their hysteretic load–displacement curves is mitigated. When the number of the connection-to-floor screws of the angle brackets was increased from 10 to 14, the shear resisting capacity of the angle brackets can be enhanced by 6.43%, and their shear strength degradation can be relieved by 12.85–56.25%. For the CLT wall-to-floor angle brackets, the analytical interaction diagram can be described using one bilinear function, which consists of the ratio between the shear to the shear resistance and the ratio between the tension to the pull-out resistance.

On the mooring methodology of heaving point absorber arrays

This paper aims at developing a mooring methodology for floating point absorber arrays. To date, the literature gives no clear indications of the mooring influence on the potential energy conversion of a floating wave energy converter. Hence, this study targets to provide general insights into the dynamics of a floating wave energy converter under the influence of moorings. These are gained by conducting an experimental study on the motion response of a wave energy converter array in regular wave conditions using three different mooring systems: a taut line mooring, a vertical tension leg mooring, and a conventional slack catenary mooring. Results show that the potential energy conversion is strongly influenced by the choice of the mooring system and the incident wavelength. In intermediate wavelengths, a taut mooring system leads to a 8% increase in energy conversion potential. In contrast, the tension-leg moored array exceeds the potentially converted energy of the catenary moored array in wavelengths significantly longer than the wave energy converter’s length by over 80%. The results of this study provide an insight into the site-specific design of point absorber arrays and the best choice of the mooring system to increase the potential power output.

Characteristics and mechanism of Jiaocheng ground fissure in Taiyuan Basin, China

The Fenwei Basin, which has 612 developed ground fissures, is the most concentrated and severe area in China and even the world for ground fissure hazards. The Jiaocheng ground fissure in the Taiyuan Basin is known for being the longest length and causing the most damage and impact in China. To discover the origin of the Jiaocheng ground fissure, surveying, trenching, and geophysical exploration were used to study its geological basis, developmental characteristics, and genetic processes. With a total length of 46 km and an impact bandwidth of 80–120 m, it is one of the longest ground fissures found in the world. The fissure is located on the hanging wall of the Jiaocheng fault, and the NE strike is quite consistent with this fault. Houses, roads, fields, and other structures have all been damaged to varying degrees by the fissure. The most common movements are vertical slip, horizontal tension, and right-lateral slide. According to trenching and shallow seismic profiling, this fissure has synsedimentary features. The Jiaocheng ground fissure was formed due to the interaction of several forces. First, the Jiaocheng fault shifted because of regional extension, creating a rupture system in the surface strata. Pumping activity contributed to the formation of the current ground fissure. This research has significant implications for understanding fissure mechanics and preventing and mitigating ground fissures.

Turning motion of multi-connection cross-flow vertical axis offshore wind turbines tension moored at a single point

Turning motion of multi-connection cross-flow vertical axis offshore wind turbines tension moored at a single point

Similarity Model Test on Stress and Deformation of Freezing Pipe in Composite Strata during Active Freezing

In order to prevent the problem of freezing pipe fracture in the process of artificial freezing construction, taking the main shaft freezing project of Shandong Yuncheng Mine as the background and based on the similarity theory, the similarity model test of freezing pipe in the composite stratum of the active freezing section is carried out. The test results show that the distribution of freezing temperature field in sand layer and clay layer is “W”-shape, and the temperature at the interface of outer ring pipe is slightly higher than that of the inner ring pipe. The change rate of freezing temperature can be divided into three stages: rapid decreasing section, slow decreasing section, and stable section. Compared with the clay layer, the sand layer has the shorter freezing closure time and the lower freezing average temperature. The frozen pipe is always in the state of vertical compression in the clay layer, while in the state of vertical compression first and then vertical tension in the sand layer. The maximum compressive strain in the clay layer is −305 με, which is equal to the vertical compressive stress of 64.1 MPa. The maximum tensile strain in the sand layer is 406 με, which is equivalent to the tensile stress of 85.2 MPa. The bending direction of different freezing pipes is different in the different soil layers. The maximum bending strain of the frozen pipe in the clay layer is 779 με, which is 2.6 times the vertical strain at the same location, corresponding to the bending stress of 163.4 MPa and reaching 0.69 times of the yield limit of frozen pipe, while the bending strain in the sand layer is very small. The vertical strain and bending strain of freezing pipes at the interface of soil layers are very small, but the bending strain is still dominant.

Natural Umbilicoplasty Without Visible Scarring: An Easily Taught and Reproducible Technique

Abstract Goals/Purpose The umbilicus is a focal point in an abdominoplasty, but the variety of published techniques can create confusion when deciding which incision is optimal for inset. Recently, an excellent technique was described that results in a scarless caudal umbilicus with superior hooding (2022 Samargandi). A similar technique has been used by this abstract’s senior author (J.G.) for over 20 years and has subsequently been implemented in our residency training. The inset is accomplished through an inverted-V incision in the abdominoplasty flap. The technique avoids excessive vertical tension on the abdominoplasty closure, a complicating factor of aggressive abdominoplasty advancement that can lead to vascular compromise in the inferomedial aspect of the flap. Insetting the umbilicus prior to resection of this inferior excess can allow for greater advancement of the abdominoplasty and decreased risk of flap over-resection. Methods/Technique The umbilical inset through an inverted-V incision in the abdominoplasty flap has been performed in all the senior author’s (J.G.) patients over the past 20 years. Following inferior wedge resection of the native umbilical stalk, the apex of the inferiorly based (inverted-V) flap is sutured to the dermis of the umbilical stalk and to the rectus fascia. The superolateral margins of the native umbilicus are approximated to the abdominoplasty skin. The sole deep suture inferomedially tethers the most visible aspect of the umbilicoplasty to the abdominal wall. The inverted-V incision in the abdominoplasty flap prior to low transverse closure increases the vertical tension on the flap and enables a safe resection of the inferior excess tissue. This technique has been taught to all residents in our training program and quickly incorporated in our abdominoplasty closures. Results/Complications Incising the inverted-V in the abdominoplasty flap eases tension on the low transverse wound closure. All residents have been able to independently perform this technique. Among the patients who have undergone this technique, none have experienced necrosis of the inferior aspect of the abdominoplasty flap or of the umbilical stalk base. As gravity encourages relaxation of the abdominoplasty skin, the superior aspects of the umbilicoplasty are overshadowed by the resulting superior hooding. This technique yields a natural-appearing umbilicus with adequate depth and a camouflaged inferior inset. Our patients frequently comment on the “untouched” appearance of their umbilici. No patients have required revisions of the umbilical inset, and none have experienced necrosis of the inferomedial aspect of the abdominoplasty flap. Residents have reported quick integration and predictable umbilical positioning with this technique. Conclusion The technique is easy to teach and can be rapidly incorporated by surgeons in practice, as well as in training. We are excited to see this technique having recently been described and feel strongly that its widespread adoption should be entertained. The inset during abdominoplasty flap advancement, prior to final resection of the inferior excess skin, can simplify decision-making for where to position the umbilicus and how much inferior excess tissue to resect. In addition to realizing the aesthetic superiority of this umbilicoplasty technique, it is important to proclaim the benefit of insetting prior to final abdominoplasty closure and the intuitive sense with which the new position of the umbilicus can be determined.

Icing detection method of 500 kV overhead ground wire with tangent tower under special terrain based on vertical tension measurement technology

The operation reliability of the power grid and the stability of social production are seriously threatened by the icing of the overhead line. The equivalent ice thickness (EIT) is to convert different densities and shapes of ice into the uniform annular ice with density of 0.9 g/cm3. Although many methods for calculating EIT of transmission line conductors have been proposed, there are lack an effective monitoring method of EIT for 500 kV ground wire with tangent tower under the special terrain where “the virtual lowest point” of the ground wire appears in the condition of large height difference. Therefore, a calculation method of EIT for 500 kV ground wire with tangent tower under the special terrain based on vertical tension measurement technology is proposed. That is the iterative method is used to preset different EITs. Then the calculated vertical tension under the preset values are solved by the established ground wire state equation and vertical tension equation. The EIT can be obtained when the calculated vertical tension is equal to the measured vertical tension. The comparison between the artificial observed EIT and the calculated EIT is carried out for two practical cases of 500 kV ground wire in the mountainous area of southern China. The results show that the absolute error is less than 2 mm, which verify the two values are in strong agreement. The corresponding finite element simulation models are established. A comparative study between the simulated EIT and the calculated EIT is carried out. The results show that the relative error is less than ±10% under severe icing from 10 mm to 30 mm and the absolute error is less than 1 mm under mild icing of 5 mm, which verify the two values are highly consistent. Finally, the application effect of this method in practical cases is analyzed.

Structure- and lithofacies-controlled natural fracture developments in shale: Implications for shale gas accumulation in the Wufeng-Longmaxi Formations, Fuling Field, Sichuan Basin, China

Descriptions, field emission-scanning electron microscopy and geochemical analyses on shale core samples taken from the fractured intervals of the Wufeng-Longmaxi Formations in three wells from the Fuling Field were used to understand the developmental properties of natural fractures and elucidate their controlling factors. Furthermore, the effects of geological fractures on shale gas accumulation were systematically analyzed. The macro-fractures observed in the shale cores are mainly non-tectonic bedding fractures; to a lesser extent, tectonic fractures, including oblique shear, vertical tension and tension-shear fractures, as well as bed-parallel slip fractures are visible. In contrast, micro-fractures are mainly interparticulate, intraparticulate, and grain marginal in nature. The extent of natural fracture development is controlled by external structural and internal lithofacies factors. For shales with similar lithofacies, the development degree of tectonic fractures increases with decreasing distance from the tectonically deformed and faulted zones. Within the same structural zone, the fractures are well developed in shales of organic matter-rich S-3 (i.e., argillaceous-rich siliceous) lithofacies. The study of fracture properties and their controlling factors has resulted in a model for the development of natural fractures in Wufeng-Longmaxi Shales generated by both structural and lithofacies effects. Overall, shale reservoirs in a “fractured but not broken” state are the most favorable ones for gas accumulation.

Perbandingan Hasil Analisa Perhitungan Rangka Kuda-Kuda Kayu Dengan Menggunakan SAP-2000 dan Metode Titik Buhul

This research is a study that discusses the comparison of the results of the analysis of the calculation of the forces on the wooden framework using the Structure Analysis Program-2000 (SAP-2000) and method of joint. The value of each force of vertical bars, horizontal bars, tensile bars, and compression members at each point of the wooden framework will be calculated on three wooden framework spans with spans of 7m, 9m, and 11m. Comparison of the results of the calculation of the value of the rod force from the two methods will be compared to see the efficiency of the calculation analysis of the two methods. From the results of the calculation of the method of joint and the Analysis of Structure Analysis Program-2000 (SAP-2000) in calculating and analyzing the value of each vertical bar force, horizontal bar, tension member, and compression member, the difference between each rod force is at (0- 0.51) kg. This shows that the calculation analysis using the Structure Analysis Program-2000 (SAP-2000) is faster and more efficient in calculating each bar force.

Different Surgical Techniques in the All-on-4 Treatment Concept: Evaluation of the Stress Distribution Created in Implant and Peripheral Bone with Finite Element Analysis.

To examine the stresses caused by different All-on-4 surgical techniques-conventional, a combination of monocortical and bicortical, bicortical, and nasal floor elevation-on the implant and the surrounding bone using 3D finite element analysis (FEA). A 3D bone model of the atrophic maxilla was created based on CT imaging of the fully edentulous adult patient. All implants used in the models were 4 mm in diameter, and the length was 13 mm in the anterior and 15 mm in the posterior. Implants were applied to four different atrophic maxillary models with the All-on-4 technique: anterior and posterior monocortical implants in the first model, anterior monocortical and posterior bicortical in the second model, anterior and posterior bicortical in the third model, and anterior and posterior bicortical with nasal floor elevation in the fourth model. Eight linear analyses were performed by applying force from both vertical and 45-degree oblique directions to the four models prepared in our study. When the cortical and cancellous bone around the anterior implants was examined, it was observed that the oblique and vertical loading conditions and the stresses around the implant were similar in all models. When the posterior implants were examined, model 1 (ie, anterior and posterior monocortical implants) showed the greatest oblique compression, vertical compression, and vertical tension forces. According to the Von Mises stress (VMS) analysis results for anterior and posterior implants, higher values were observed in model 1 compared to models 3 and 4 under oblique and vertical forces. It was observed that bicortical placement of the implants reduced the stresses on the bone and implant-abutment system but had no significant effect on the stress on the bar. According to the results of our study, in the All-on-4 technique, bicortical placement of the implants reduced the stresses on the bone and implant when the anatomical limitations allowed. In addition, nasal floor elevation can be applied in the atrophic maxilla in appropriate indications.

Discrete Element Simulation of Fracture Evolution around a Borehole for Gas Extraction in Coal Seams.

The stability analysis of underground caverns, tunnels, and boreholes is of great significance to underground engineering. In order to study the stress change of the coal around a hole and the evolution law of fractures during the coal seam drilling process, the discrete element simulation of the coal seam drilling process was carried out by using the particle flow code (PFC2D). The results show that during the drilling process, under the influence of confining pressure and drilling disturbance, the coal stress field around the hole and the development of fractures around the hole have the characteristics of zoning and dynamic evolution. In the axial direction of the borehole, it is divided into front and rear areas, and in the vertical axial direction, it is divided into the drilling disturbance zone and the confining pressure main control zone. During the drilling process, the direction of the maximum principal stress in the front zone gradually changes from the vertical hole axis to the direction parallel to the hole axis, and tension fractures are mainly developed along the drilling direction. In the rear zone, the principal stress direction tends to be stable and the principal stress value undergoes dynamic changes, and a large number of vertical hole axis tension fractures are developed. The drilling disturbance zone appears near the hole wall and has an important influence on the stability of the hole wall, while the confining pressure main control zone determines the antireflection effect around the hole and the influence radius of the hole. This work helps the understanding of the damage range and failure characteristics of the surrounding rock during the drilling process and has great significance for the guidance of drilling design.

Numerical analysis of the influence of coal pillar size on auxiliary tunnel stability

It is very important to study the stability of the tunnel in the area affected by mining activities. In particular, the choice of coal pillar size has a direct influence on the stability of these tunnels. The authors of this study used the Flac3D program to model a mining face LC1 with various coal pillar sizes. The 220 m-long mining face known as LC1 has 20 degrees rock mass layers. The studied coal pillars are various widths at 5 m, 8 m, 10 m, 15 m, 20 m, and 30 m. The highest vertical stress and maximum horizontal stress are placed at different locations along the lower mining face (LC2), as shown by the results of the numerical simulation. The pressure distribution of the rock mass on the tunnel's top and the level of stress concentration on its two sides are asymmetrical for inclined seam conditions. The position of the maximum vertical tension is expected to change from the left hip to the side of the coal pillar as the coal pillar widens. This change essentially marks the system's transition from one stable state to another. Due to the rock mass's weak stability during this transition, the support must be strengthened in order to improve the rock stability.

Engineering-geological assessment of rocky soils based on the analysis of the collection of Albazinskoye deposit samples

The article deals with the engineering-geological assessment of the rocky soils of the Albazinskoye deposit located in the north of the Khabarovsk Territory, Russia conducted on the example of the analysis of the collection of samples of various petrographic types of certain geological formations. The purpose of the research is to implement a specially developed complex methodological scheme including an optical method (analysis of thin rock sections), measurement of seismic (surface and through sounding of samples to determine longitudinal seismic wave velocity), strength (vertical compression and tension) and physical (density and water absorption) properties. Using the obtained data, a comparative analysis of samples is performed based on the results of seismic, strength and physical properties taking into account petrographic information. Anisotropy in terms of seismic and strength properties is established. Using a cluster analysis program, the correlation coefficients between property indicators are determined. On example of the materials of the collection, it is shown that the differences in the velocity of longitudinal seismic waves and strength are determined by the textural-structural features and composition of rocky soils, which are studied at the micro level.

Study of undisturbed soil test about slope angle of the expanded-plate affecting the failure mechanism of the NT-CEP pile under vertical tension

In this paper, it is computer simulation studied that the influence of the slope angle of expanded-plate of the new-type concrete expanded-plate pile (the NT-CEP pile) to the uplift failure mechanism. The model piles of different slope angle are designed in undisturbed soil test, in which the effect about the bearing capacity of the NT-CEP pile and the failure behavior of the soil is analyzed, at the same time, the computer simulating analysis of finite element is assistant by the ANSYS software, to verify the test results. The innovation of this paper is mainly to test research methods, which improves and innovates the existing model test method and test equipment because of completing the test with undisturbed soil and ensuring the reliability of the test results. The research results of this paper will enrich and improve the design theory of the NT-CEP pile and play a necessary complement to the practical engineering application and a positive role in promoting the research and application of the NT-CEP pile.

Failure analysis and deformation mechanism of segmented utility tunnels crossing ground fissure zones with different intersection angles

Ground fissures are a special urban geological disaster within the city of Xi’an. The differential settlement between strata can cause ground cracking and severely threatens the safe construction and operation of underground engineering. This study establishes a 3D-FDM calculation model of different intersection relationships between the segmented utility tunnel and the ground fissures using Flac 3D software. The influence of the intersection angles on the deformation and failure characteristics of the structure was analyzed. The results show that the segmented utility tunnel presents with the deformation characteristic of three-dimensional movement under the action of the ground fissures. The deformation between structures is primarily vertical dislocation, horizontal tension, and compression, indicating that the structure may be subjected to a bending-torsion failure. The vertical settlement of the roof of the utility tunnel shows the deformation characteristics of three broken lines. The third and fourth structures have a significant differential settlement, showing a negative correlation with the intersection angle. The segmented measures can eliminate the void area at the bottom of the hanging wall in the utility tunnel; however, when the intersection angle is ≤30°, the contact pressure at the bottom is close to 0, indicating that the intersection angle has a significant impact on the formation of the void areas. In addition, the calculation method of the vertical settlement of the segmented utility tunnel crossing the ground fissure zone is also proposed. It has proven to be effective in calculating the vertical deformation of the structure. This study provides scientific guidance for constructing utility tunnels within ground fissure development areas.