Strata Movement of the Thick Loose Layer under Strip-Filling Mining Method: A Case Study

Filling mining plays an important role in controlling surface subsidence. To study the movement of overburdened rock in filling mining under thick loose layers, a numerical simulation combing field measurement in CT30101 working face in the Mahuangliang coal mine was tested. The results show that different filling rates and filling body strength have different influences on roof and surface movement. The filling rate has a greater impact, which is the main control factor. The filling stress and roof tensile stress decrease gradually with roadway filling. The filling body stress and roof tensile stress in the first and second rounds are far greater than in the fourth round. After the completion of filling, the first and second round of filling bodies mainly bear the overburden, and the total deformation of the surrounding rock of the main transport roadway is very small, and therefore the displacement of the overburdened rock is controllable. The field monitoring results also show that the overburdened rock became stable after several fillings rounds. Combing the numerical modeling and field tests results, this study can be a guideline for similar geological conditions especially for coal mining under thick loose layers and thin bedrock.

RECONSTRUCTION OF THE FEMALE UROGENITAL COMPLEX IN THE PRENATAL PERIOD OF ONTOGENESIS

In 9-weeks prefetuses, urogenital complexes are located lower than in prefetuses of previous age groups. In the vertical sections of the urogenital cords, the paramesonephric ducts diff erentiate into the uterine tubes. Above the entrance to the pelvis, the urogenital cords pass obliquely in the vertical direction, at the level of which the paramesonephric ducts are connected, on both sides of which the mesonephric ducts are located. The primary kidneys are completely reduced in their upper two-thirds, the reduction of mesonephric cells in the lateral areas of the lower third of the kidneys begins. The caudal divisions of the paramesonephric ducts touch dorsally to the wall of the urogenital sinus, while the lower ends of the mesonephric ducts are in the thickness of the wall. The urogenital cords (mesonephric and paramesonephric ducts) protrude above the upper ends of the primary kidneys and below the permanent kidneys. The mesonephric and paramesonephric ducts are clearly demarcated by a layer of loosely spaced mesenchymal cells.In 10-weeks prefetuses, due to the connection of the lower vertical parts of the paramesonephric ducts, a common uterine- vaginal canal is formed, lined with pseudolayered epithelium. Mesonephric ducts retain their lumen in fragments.In 11-weeks prefetuses, the upper vertical sections of the urogenital cords, in connection with the reduction of the mesonephric ducts, contain mainly paramesonephric ducts, which are separated from each other by a loose layer of the mesenchyme. From these sections of paramesonephric ducts uterine tubes are formed. Oblique (middle) sections of the paramesonephric ducts with further development are transformed into intrauterine parts of the uterine tubes. The lower caudal sections of the paramesonephric ducts are transformed into the uterus and the upper two-thirds of the vagina.In 12-weeks prefetuses, the primary kidneys are almost completely reduced. Only single mesonephric tubules within their caudal area are determined. In parallel, there are intense processes of formation of internal female reproductive organs. The cranial ends of the uterine tubes expand, acquiring a funnel- shaped shape. The outer border of the infundibulum of the tube reminds a zigzag line, which is evidence of the beginning of the formation of the fi mbria of the uterine tube. The lumens of the mesonephric ducts are reduced to 6±0.1 μm, and in some parts of their walls are in contact with each other. Transformation of paramesonephric ducts into their derivatives (uterine tubes, uterus, upper part of the vagina) is accompanied by corresponding histological changes of their walls.

Analysis on Subsidence Law of Bedrock and Ultrathick Loose Layer Caused by Coal Mining

In the process of coal mining, when the buried depth is large and the loose layer is thick, the ground subsidence tends to be abnormal, thus causing great damage to the surface ecological environment. In order to reveal the mechanism of mining ground subsidence under ultrathick loose layer, taking 1305 working face of a mine as the background, the law of mining ground subsidence under ultrathick loose layer was analyzed through field measurement. The law of bedrock subsidence is analyzed by similar simulation test, and the role of ultrathick loose layer in bedrock subsidence is quantitatively analyzed. The hydrophobic settlement model of ultrathick loose layer is established by settlement theory calculation, and the law of ground subsidence caused by hydrophobic of ultrathick loose layer is analyzed. The results show that the ground subsidence is mainly composed of bedrock subsidence and hydrophobic settlement of ultrathick loose layer. The maximum ground subsidence measured in the field is 4.201 m, the bedrock surface subsidence obtained by the simulation test of similar materials is 3.552 m, and the subsidence of ultrathick loose layer obtained by hydrophobic settlement analysis is 0.58 m. Adding the subsidence of bedrock surface and the subsidence of ultrathick loose layer, the ground subsidence is 4.132 m. It is in good agreement with the total ground subsidence measured in the field, which verifies the rationality that the ground subsidence mainly includes bedrock subsidence and hydrophobic settlement of ultrathick loose layer.

Study on Deformation and Failure Characteristics of Weak Cemented Roof in Shallow and Extra Thick Coal Seam Mining

Detecting the development height of water flowing fractured zone in the roof of coal seam is of great significance for the roof safety of working face with developed sandstone and thick loose layer. This paper analyzes the influence of the induced polarization effect of electrode on the traditional single-mode parallel electrical method. In order to avoid this interference, the dual-mode parallel electrical method is applied to monitor the roof deformation and failure of a coal mine in Ordos Basin. The monitoring results show that: under the influence of mining, the change of geoelectric field of coal seam roof is dynamic, the apparent resistivity of initial mining fracture is high, the apparent resistivity of surrounding rock water filling mining fracture is low, and the apparent resistivity of fracture water flowing to goaf is high again. According to the characteristics of geoelectric field, the maximum height of water flowing fracture zone is 122 M; The average mining coal thickness of the working face is 11 m, and the fracture / mining thickness ratio is 11.1. The results of plastic zone show that the maximum height of water flowing fractured zone above the working face is 122 m, which is consistent with the test results. The vertical stress response characteristics of roof monitoring points are zonal. Under the influence of mining, the loose layer near the surface above the working face is cracked. The edge type ground fissures exist for a long time, and there are a series of geological problems such as soil erosion, ground subsidence.

Study on Numerical Simulation Test of Mining Surface Subsidence Law under Ultrathick Loose Layer

In the process of coal mining, the surface subsidence under ultrathick loose layer is abnormal (subsidence coefficient greater than 1.0), which will cause great damage to the surface ecological environment. The fracture propagation and stress evolution of bedrock are of great significance to the prevention of surface subsidence. Taking the 1305 working face of a mine as the background, this paper study the process of crack propagation and stress evolution of bedrock under the influence of ultrathick loose layer by methods of on-site measurement, similar simulation, and numerical simulation. During the research process, the physical model was verified by the measured data. Then, the numerical model was verified by the crack propagation angle and subsidence of bedrock, which were obtained in a similar simulation. Based on the verified numerical model, it was obtained that after the coal seam was mined out, the bedrock above the mined-out area was mainly damaged by tension, while the strata on both sides of the crack expansion angle were mainly damaged by shear and tension. During coal seam mining, for bedrock the process of fracture expansion, subsidence, and stress evolution all could be divided into four stages. This research provides a basis for the control of surface subsidence.

3-D dynamic simulation of knitwear based on the hybrid model

Due to the effect of force and deformation of fancy stitches, the simulation of knitwear is facing a great challenges of the real-time. In this paper, the physical-geometric hybrid method is applied to reduce the amount of calculation during the simulation of knitwear. Discretized Newton’s Method is used to analyze the gap between dynamic knitwear-human body and the knitwear model, and then the knitwear model is further divided into different regions. A three-dimensional (3-D) mesh for knitwear is constructed by the application of adaptive remeshing. This makes it possible to refine the mesh at the parts that need the presentation of fabric surface details. Simultaneously, it can merge the adjacent patches at parts without the requirement of showing the details, and form a large 3-D patch. In the light of regional division, the 3-D knitwear model is divided into the tight layer, floating layer, and loose layer. In addition, the geometric loop model based on the cuboid particle system is employed to simulate the real force of loops and knitwear for tight layer and loose layer. Near-rigid deformation method is also applied into the floating layer to improve simulation efficiency. In conclusion, the corresponding processing method is performed with different computational models, which brings the dynamic simulation effect of knitwear with realistic and real-time.

A prediction model of mining subsidence in thick loose layer based on probability integral model

The probability integral method is the most commonly used mining subsidence prediction model, but it is only applicable to ordinary geological mining conditions. When the loose layer in the geological mining conditions where the mining face is located is too thick, many inaccurate phenomena will occur when the movement deformation value is predicted by the probability integral method. The most obvious one is the problem that the predicted value converges too fast compared with the measured value in the edge of the sinking basin. In 2012, Wang and Deng proposed a modified model of probability integral method for the marginal errors in the model of probability integral method and verified the feasibility of the method through examples. In this paper, the method is applied to the prediction of surface movement under thick and loose layers after modified. Through practical application, it is found that due to the angle between the working face and the horizontal direction, the average mining depth in the strike direction is different from the average mining depth in the inclined direction, and the main influence radius of the two main sections are often. Therefore, based on this problem, this paper divides the main influence radius into trend and tendency and adjusts the parameters in the model to find the rules of the parameters. The original method uses a dynamic scale factor to adjust the predicted shape of the graph by adjusting the sinking coefficient. This study is aimed to set the scale factor to 0.5 and fix the value of the sinking factor, and propose to adjust the integral range and then adjust the shape of the graph to make it more in line with the actual measurement situation.

Overburden Migration and Failure Characteristics in Mining Shallow Buried Coal Seam with Thick Loose Layer

Quite a number of shallow buried coal seams (SBCS) are distributed in China. The overburden is easily damaged due to the mining of SBCS, resulting in water resources loss and surface damage. Taking 12403 working face of Wulanmulun coal mine in Shendong mining area as an example, this paper analyzed the overburden migration and failure characteristics after mining SBCS with thick loose layer based on actual measurement data and simulation results. The results show that the subsidence of strata in caving zone has no skewness feature along strike direction, while the subsidence of strata in fracture zone and bending subsidence zone shows skewness subsidence phenomenon. An interface exists in the overburden, and the movements of upper and lower strata at the interface have different characteristics. The cracks penetrating the whole strata exist in bedrock, not in aeolian sand. The height of water flowing fracture zone is 35.74 m–62.89 m according to the loss of fluid in the borehole and consistent with the results of numerical simulation and similar simulation. This study can provide a reference for the prediction of the height of water flowing fracture zone and the overburden migration in mining SBCS.

Geographic variation in skin structure in male Andrew’s toad (Bufo andrewsi)

Variation in organ structure likely provides important clues on local adaptation and reflects the pressure target of natural selection. As one of the important organs, the skin plays a key role in adapting to complex environments by reducing water loss or increasing water absorption. Nevertheless, variation in the skin structure across different populations in a single species of anurans remains enigmatic. Here, we studied geographical variation in the skin structure of male Andrew’s toads (Bufo andrewsi) across ten populations using histological methods. We quantified thickness of the skin, the epidermis, the loose layer, the compact layer, and of the epidermis, area of granular glands (GGs) and of ordinary mucous glands (OMGs), width of the calcified layer, and number of capillary vessels. We found that the thickness of the skin, dermis and loose layer in dorsal skin increased with latitude whereas the area of granular glands decreased with altitude. Moreover, the width of the calcified layer in ventral skin decreased with latitude among populations. Our findings suggest that geographical variation in skin structure in male B. andrewsi is likely to reduce water loss or make water absorption occur faster in complex high-latitude environments, improving local adaptation.