Study On The Surrounding Rock Stability And Safety Control Of Roadways Roof Embedded Weak Intercalated Seam

Weak intercalated seam is a very disadvantage geologic condition for roadway digging. It makes roadway easy to become separation in roof even falling in safety construction and long maintenance, it is one of the biggest hidden trouble to mining roof safeties.Based on the background of roadway construction and support, the paper systemically studies on the basic capability and the stability rule of roadway surrounding rock embedded weak intercalated seam by using the techniques of lab rock block experiment, plane strain similar material simulation experiment, numerical simulation analysis, theory analysis, calculator program and industrial experiment, resulting in bringing forward the countermeasure of the roadway safety construction and surrounding rock stability.The thesis analyzes the physical and chemical characteristic of weak intercalated seam, and studies its physical and mechanics parameters, especially the location which influences on roadway roof stability. On the basis of lab testing mechanical character, put emphasis on studying stability-lost character and failure mechanism for mud-rock roadway in the effect of water and weak intercalated seam roof roadway in the effect of dynamic pressure.Particularly analyze the weighing of each influence factor on stability of weak intercalated seam roof roadway. Bring forward the new concept of safety factor for weak intercalated seam roof roadway, and measure off the rank of safety status. Via computer VB program the safety rank is evaluated before making some strength support scheme. Establish safety control technique system aimed at weak intercalated seam roof roadway. At last, make checkout by typical project examples. The main conclusions are as follows:(1)By means of locale drill hole observation, it can be found that weak intercalated seam of the roof are mainly made of thin muddy rock, coal line, crack belt or cleat and so on, which is less than 300 mm; Through X-Ray diffraction experiment to analyze the component of mudded muddy rock , it can be found that the composition of the clay is high, more than 70 percent, it is apt to combined with water and easy to be mudded; Under the effect of chemistry, physics, mechanics and other factors, this kind muddy rock is quite easy to be weathered, resulting in its mechanics character and strength decreased seriously, the danger of roadway increases greatly.(2)By experiment of fractured rock mass's cement mortar in lab, it obtains the changing rules of cohesion C and friction angleφfor cemented concretion of sandstone and mud-rock in the circumstance of different supports. With support strengthened, the stronger rock's cemented concretion C is increasing, andφis decreasing. But the weaker rock is contrary. It provides strong conduction for support selection and value in the locale engineering practice.(3)On the basis of testing mechanical character of rock blocks without water in the lab, by ways of FLAC numerical simulation and the theory analysis, the physical and mechanical characters have been researched, especially influence rule on separation of weak intercalated seam location. Weak intercalated seam losses stability instantly and could not load while digging the roadway. The biggest separation occurred when weak intercalated seam is at the edge of bolt support region. By the rock test with water, analyze mudded character of the mudded rock, and research displacement field, stress field and seepage field of mudded roadway in the effect of water by FLAC numerical simulation. The displacement field has been largely disturbed by the water effect. The displacement of surrounding rock has been sharply increasing while the deformation velocity is accelerating continually. After the long-term effect, the support doesn't have any function more, the surrounding rock lost bearing capacity and then the whole roadway is unstable and collapse.(4)By means of the similar material simulation experiment of plane strain in the lab, the unstable process that the weak intercalated seam under different places and dynamic pressure has bed-separation and collapse has been researched. It is can be acknowledged that this kind roadway under the initial stress can keep stability after bolt support, but weak intercalated seam presents the obvious separation in the circumstance of high stress or dynamic pressure (double or treble initial stress). As the stress increased, the roadway will soon fall; with the horizontal stress increased continuously, its separation becomes larger, leading to accelerating stability-lost and fall. It also proves the conclusion of numerical simulation.(5)Aiming at stability-lost character and failure mechanism of weak intercalated seam, detailedly analyzes the weighing of each influence factor and assign the weighing reasonable, and put forward the conception of safety factor AQ which stands for the safety rank, five ranks in all (more dangerous, dangerous, safe, safer, safest). At the same time achieve the safety rank evaluation of roadway roof of this kind by the computer VB program. So it can have more pertinence in adopting various strength control technology for the roadway safety.(6)Establish safety control technique system of weak intercalated seam roof roadway. It mainly includes roof safety evaluation technique and combination control technique system. The former is made up of lithology Exploration technology, support monitor technology and data processing and feedback technology; the latter consists of support technology of pretensioned force and high-powered bolt without water and combined control technology under dynamic pressure and water action. It is applied in the locale project's practice in the typical conditions of Huaibei diggings like weak intercalated seam at the edge of bolting-support region, where is under the circumstance of no water (Luling Coal Mine), water and even the dynamic pressure (Xutuan Coal Mine), making good achievement.