Joint Fissures Research Articles

Study on Sensitivity Parameters Analysis of Grouting Reinforcement Underpassing Existing Subway Tunnel by Numerical Modeling

When carrying out construction that underpasses existing subway tunnels, the surrounding rock is frequently disturbed. Therefore, it can loosen easily and become unstable, which makes its stability difficult to control. Here, we considered an existing subway tunnel in a certain subway section and used orthogonal experiments to design a simulation program as well as the UDEC (Universal Distinct Element Code) simulation software to determine the influences of four factors (i.e., grout density, grouting pressure, dynamic shear force, and viscosity) on the grouting reinforcement effect. The following results were obtained: (1) the combination of the construction method and the grouting parameters strongly influences the reinforcement effect on the surrounding rock of the tunnel. The grouting pressure is not directly proportional to the stability of the surrounding rock. The dynamic adjustment of the relationship between the grouting pressure and the grout density can effectively improve the stress state of the surrounding rock of the tunnel, control surface settlement and deformation, and reduce the section reduction rate of the tunnel. (2) The distribution of joints is closely related to the failure area and form of the surrounding rock of the tunnel. For surrounding rock with well‐developed joint fissures, an excessively high grouting pressure should not be used as they are unstable. (3) The effective bearing range of grouting‐reinforced surrounding rock is dependent on the pore pressure and principal stress difference. The area where the pore pressure is 70–80% of the initial grouting pressure is the effective bearing range of the grouting‐reinforced surrounding rock. The stability of the surrounding rock increases with decreasing principal stress difference and increasing range. (4) The actual monitored data show that the surface settlement can be effectively reduced by handling of grouting reinforcement parameters flexibly, which can meet the control standards.

Comprehensive Engineering Geological Analysis on Large-Scale Anti-dip Slopes: A Case Study of Changshanhao Opencast Gold Mine in China

Flexural toppling failure of large-scale anti-dip slopes constitutes a significantly rare phenomenon. With regard to the large-scale anti-dip slope instability at the southwest stope of Changshanhao Opencast Gold mine, in this work, a field engineering geological survey on the Changshanhao open stope was conducted, to investigate the structural plane features of the corresponding slope rock mass. Moreover, an equatorial horizon projection and strike rose diagram were utilized to determine the preferred structural plane of the joint fissures; the exposed rock mass integrity zoning of slope and the rock sample property testing on the main lithological compositions in the stope were also established. Based on the results of previous field investigations and indoor rock mechanics experiments, along with the occurrence conditions of stratigraphic structures unmasked by existing engineering geology borehole data, geographical explorations and mining engineering, the failure mode of southwest stope slopes were also determined. Finally, several suggestions were provided on the reinforcement and treatment of dangerous slopes within the ultimate mining boundary, consequently laying a foundation for sustainable safe mining.

Study on the characteristics of karst development in Beijing

The distribution area of carbonate rocks in Beijing is about 5071.44 km2, accounting for 30.19% of the land area in Beijing. The distribution areas of bare, covered and buried carbonate rocks are 2862.21 km2, 401.86 km2, 1803.37 km2, respectively. The carbonate rocks mainly includes dolomite in Changcheng Group of Jixian System (Jxg), dolomite in Wumishan Group of Jixian System (Jxw), dolomite in Tieling Group of Jixian System (Jxt), Cambrian limestone (Є), Ordovician limestone (O) and carbonate rocks with different ages. The characteristics of karst development in Beijing differ from region to region. In the mountainous areas of dolomite in Changcheng System and Jixian System of Proterozoic, the karst landforms such as hoodoos, series of peaks and gorges are formed by the influence of rock differential solution and shear joints. In the Cambrian and Ordovician limestone distribution areas, middle-low mountains and uvalas are formed; the covered karst is affected by rock composition, regional structure control and environment, and the degree of karst development varies in different regions. According to the ground karst, karst caves distribution and karst spring distribution in Beijing area, the karst development in Beijing is summarized into three types: karst system-based (mainly developed karst cave system), fissure-based (basically undeveloped caves and karst springs, mainly for the development of underground joint fissures in the concealed area) and composite type (the karst spring with relatively large distribution, and a small number of ground karst caves, and the development of underground joint fissures). According to the distribution characteristics of 271 karst water boreholes, 563 geothermal boreholes, 258 ground surface karst caves and 499 karst springs in Beijing, the karst development in Beijing also has typical characteristics of heterogeneity, stratification and staging.

Safety Evaluation of Underground Caverns Based on Monte Carlo Method

In order to study the influence of joint fissures and rock parameters with random characteristics on the safety of underground caverns, several parameters affecting the stability of surrounding rock of underground caverns are selected. According to the Monte Carlo method, random numbers satisfying normal distribution characteristics are established. A three-dimensional model of underground caverns with random characteristics is established by discontinuous analysis software 3DEC and excavation simulations are carried out. The maximum displacement at the numerical monitoring points of arch and floor is the safety evaluation index of the cavern. The probability distribution and cumulative distribution function of the displacement at the top arch and floor are obtained, and the safety of a project is evaluated.

Karst Landscape and Development Features of the Cambrian Ordovician Period in Huainan Region

Huainan is located at the boundary between north and south of China. Due to its unique geotectonic location and long geological evolution history, Huainan has formed a special karst landform. The karst landscape and karst development process of the Cambrian Ordovician in this area are analyzed from the aspects of stratigraphic distribution, crustal movement evolution and groundwater recharge conditions. It is concluded that large karst caves are developed in the karst multi-shun layer in the study area, in carbonate rocks. The surface development of the joint fissures is mostly filled with calcite, the erosive gully is developed in the concentrated area of the flowing water, and the karst landscape such as the beaded karst is developed near the fault zone.

Propagation Characteristics of Blasting Stress Waves in Layered and Jointed Rock Caverns

The existence of joint fissures makes explosive actions between rock masses more complex. Therefore, it is of great significance to carry out experiments studying blasting stress waves propagating in jointed rock masses. Based on the Froude Similarity principle, the geological mechanical models of intact rock masses and jointed rocks have been proposed. A blasting vibration experiment was carried out and demonstrated that the propagation of the blasting stress waves and changing structures have an important relationship. A numerical simulation of the blasting stress wave propagation law in a layered jointed rock mass was carried out. This study found that with an increase in the joint angle, the peak velocity of blasting stress wave, transmission coefficient and reflection coefficient all gradually increased, while the attenuation coefficient gradually decreased. With an increase in joint spacing, the attenuation rate of the blasting stress waves increased.

Jointed Surrounding Rock Mass Stability Analysis on an Underground Cavern in a Hydropower Station Based on the Extended Key Block Theory

The jointed surrounding rock mass stability is of utmost importance to integral stability during the construction and long-term safety operation of the underground caverns in hydropower stations. The key blocks play a significant role in the integral stability of the jointed surrounding rock mass, therefore it is critical to determine the location, size, and failure mode of random key blocks. This paper proposes an improved method combining the traditional key block theory (KBT) and the force transfer algorithm to accurately calculate the safety factors of probabilistic key blocks in the surrounding rock mass. The force transfer algorithm can consider the interactions between the internal blocks. After the probabilistic characteristics of the joint fissures are obtained, the stereographic projection method is employed to determine the locations of dangerous joints. Then the vector analysis method is used to search the random blocks, determine the sliding directions of random blocks, and calculate the block sizes and safety factors near the free surface of the underground cavern, which can be used to comprehensively evaluate the surrounding rock mass stability. The above numerical results have provided powerful guidance for developing a reinforcement system for the surrounding rock mass.

3D identification and stability analysis of key surface blocks of rock slope

Complicated geological structures make it difficult to analyze the stability of rock slopes, such as faults, weak intercalated layers or joint fissures. Based on 3D geological modeling and surface block identifying methods, an integrated methodology framework was proposed and realized to analyze the stability of surface blocks in rock slopes. The surface blocks cut by geological structures, fissures or free faces could be identified subjected to the four principles of closure, completeness, uniqueness and validity. The factor of safety(FOS)of single key block was calculated by the limit equilibrium method. If there were two or more connected blocks, they were defined as a block-group. The FOS of a block-group was computed by the Sarma method. The proposed approach was applied to an actual rock slope of a hydropower project, and some possible instable blocks were demonstrated and analyzed visually. The obtained results on the key blocks or block-groups provide essential information for determining potential instable region of rock slopes and designing effective support scheme in advance.

Analysis of the failure of primary support of a deep-buried railway tunnel in silty clay

Abstract This paper analyses the mechanism for the failure of primary support of a deep-buried tunnel whose side wall collapses during construction. The main focus is on discussion and comparison of the soil engineering aspects of the incident, and on the lessons that may be learnt from the case. Empirical and numerical analysis have been carried out for the collapse. The mechanisms of failure of tunnel are analyzed during tunnel excavation and the parameters of support are revised according to the results of analysis. Results have shown that the collapse of tunnel is mainly attributed to abundant joint fissures on surrounding soil. The changed support makes tunnel drive through the section of collapse successfully, and similar dangerous situation does not take place in the following construction.

A traumatic case in Mammuthus trogontherii chosaricus Dubrovo (1966)

This paper describes a unique case of fusion in several bones of Mammuthus trogontherii chosaricus pes from the southeast West Siberian Plain. The fusion affected the distal ends of tibia and fibula, calcaneus and astragalus. The fusion was caused by trauma, probably by dislocation with displacement of the calcaneus and astragalus and tearing of soft tissues. As a result, a deep ankylosis caused the morphological changes of the tibia's diaphysis and distal end. X-ray study showed subtotal ossification of ankle and calcaneal-talar joints, lacking joint fissures. Signs of bone fracture healing are not apparent. The animal was injured at a young age (12–15 years). Sizes of the bones and the level of ankylosis showed that the animal died at the age of 35–40, and its death was not caused by this particular pathology.

Fokussierte muskuloskelettale Sonografie

Even in emergent situations, focused musculoskeletal sonography must not be overlooked. It has a place in traumatology no less valuable than its place in internal medicine. It can be used to identify traumatic joint effusions, occult fractures and fissures, joint inflammation, muscle and tendon rupture; it can differentiate soft tissue swelling, locate a foreign body, or identify the location of fractures. Focused ultrasound should be performed by the attending physician directly at the patient’s bedside, in order to answer these specific questions.

Failure Mechanism Analysis and Support Design for Deep Composite Soft Rock Roadway: A Case Study of the Yangcheng Coal Mine in China

This paper presented a case study of the failure mechanisms and support design for deep composite soft rock roadway in the Yangcheng Coal Mine of China. Many experiments and field tests were performed to reveal the failure mechanisms of the roadway. It was found that the surrounding rock of the roadway was HJS complex soft rock that was characterized by poor rock quality, widespread development of joint fissures, and an unstable creep property. The major horizontal stress, which was almost perpendicular to the roadway, was 1.59 times larger than the vertical stress. The weak surrounding rock and high tectonic stress were the main internal causes of roadway instabilities, and the inadequate support was the external cause. Based on the failure mechanism, a new support design was proposed that consisted of bolting, cable, metal mesh, shotcrete, and grouting. A field experiment using the new design was performed in a roadway section approximately 100 m long. Detailed deformation monitoring was conducted in the experimental roadway sections and sections of the previous roadway. The monitoring results showed that deformations of the roadway with the new support design were reduced by 85–90% compared with those of the old design. This successful case provides an important reference for similar soft rock roadway projects.

Landslide Formation Mechanism and its Control Measures in Dabaolang

Through analyzing Dabaoliang geological characteristics, this paper discussed the factors of the mechanism of landslide in Dabaoliang area and simulated its evolutionary process. The paper could get some conclusions, and the factors of landslide are as follow: the stability of the slope which mainly composed by clastic rock not only depended on the performance of the mudstone layer but also the skid resistance of the sliding surface and the shape of slope. Under the influence of regional structure, the joint fissures which developed along the boundary of the landslide will connect the crack and benefit the permeation of the surface water. The heavy rain is one of the main factors caused the slope unstable and sliding. Provide effective prevention and control for prevention and control of projects.

Deformation characteristics and mechanism of the landslide in West Open-Pit Mine, Fushun, China

The West Open-Pit mine in Fushun, NE China is currently the largest open-pit coal mine in Asia. A serious problem of slope instability has developed and is worsening. Several studies have investigated the northern slope instability, while little attention has been paid to the stability problem on the southern slope which faces northwards into the mine. Recent monitoring data show continuous deformation of the southern slope, which is a serious threat to the safe operation of the mine. In this paper, we study the deformation characteristics and mechanism of the landslide on the southern slope of the West Open-Pit mine. Our results show large deformation of the partial surface of the landslide, deep rock mass sliding, and clear sliding surface dislocation characteristics. The southern slope is a bedding rock slope with a weak interlayer. There are two faults in the study area, and the development of joint fissures promotes the internal mechanism of the landslide. The safety factor of the southern slope has decreased with the deepening of the open-pit, which shows that excavation unloading was a main triggering factor for the landslide. The mining is stripping rock mass from the bottom of the open-pit, cutting the foot of the slope and causing the rock mass to lose support. The downslide force caused by the gravity stress of the slope becomes greater than the shear strength of the weak interlayer, causing the slip body to undergo bedding slide and continuous deformation.

Study on Stabilization of Tunnel Foundations Built on Collapsible Loess

Loess soils always have lower dry densities, open structures and joint fissures, and could exhibit a significant decrease in volume due to their collapse when wetted. These soils pose potential threat on structures built on them. When a tunnel built on such soils, the bearing capacity of tunnel foundation could not always meet requirements of structural stability, and therefore need some improvements. The improvements of collapsible loess foundation include cement compaction piles and root piles.

Wellbore Stability Analysis of Coal Seam Based on Hoek-Brown Criterion

Stable evaluation of coal strength is needed in coal well-bore stability analysis. The regular analysis method of wellbore stability adopts Mohr-Coulomb strength criteria to judge the collapse pressure. Coal is dual porosity structure and contains joint fissures richly. Hoek-Brown criterion is much more reasonable to estimate the strength of jointed and fractured rock. So Hoek-Brown criterion is used to analyze the stability of multi-lateral horizontal coal bed methane well. Considering the GSI (geological strength index), structural and surface conditions of coal, the coal and rock mass strength parameters are converted into the underground coal mechanical parameters based on the triaxial test of intact coal. According to the stress state of multi-lateral horizontal well, the borehole collapse formulas are established based on Hoek-Brown Criterion. The effects on the wellbore stability, due to the joint fissures of coal, borehole size, drilling disturbance, are also discussed in this paper.

Vertebrate fissure faunas with special reference to Bristol Channel Mesozoic faunas

Abstract Throughout the Mesozoic and Cenozoic, tectonically activated joint fissures and karstic cave systems have acted as reservoirs for terrestrial vertebrate remains. They yield concentrations of microfaunal elements rarely if ever preserved in other situations. In the 1850s, Charles Moore realized their potential and exploited them to discover the earliest known mammals in late Triassic fissure infillings in the Carboniferous Limestone of Somerset. The history of that discovery and its associated problems of interpretation are recorded. His work greatly influenced succeeding generations of palaeontologists and, as techniques developed, fossil fissure discoveries have made a major impact on our understanding of vertebrate evolution.

Vertebrate fissure faunas with special reference to Bristol Channel Mesozoic faunas

Throughout the Mesozoic and Cenozoic, tectonically activated joint fissures and karstic cave systems have acted as reservoirs for terrestrial vertebrate remains. They yield concentrations of microfaunal elements rarely if ever preserved in other situations. In the 1850s, Charles Moore realized their potential and exploited them to discover the earliest known mammals in late Triassic fissure infillings in the Carboniferous Limestone of Somerset. The history of that discovery and its associated problems of interpretation are recorded. His work greatly influenced succeeding generations of palaeontologists and, as techniques developed, fossil fissure discoveries have made a major impact on our understanding of vertebrate evolution.

New modification of foot root arthrodesis

Modern literature teaches us that with extra-articular methods of surgery, graft resorption easily occurs, and primarily at the level of joint fissures, which, in the absence of ankylotic joints within the joints themselves, entails the recurrence of the dangling foot. This failure is easy to understand if we remember clinical and experimental observations showing that in the presence of pseudarthrosis of one of the paired limb bones (tibia or forearm), spontaneous pseudarthrosis of another, whole bone easily occurs at the same level (Bier et al. Biesalski, Mller, Kopylov), and that a bone graft transplanted to fix a tuberculous joint (in particular, the spine) subsequently, after healing of the lesion and disappearance of muscle stiffness, segments just at the level of the joint gap (Biesalski, Mller, Kopylov).