The creep character of anchor rod in argillaceous soft rock is remarkable. The big undisturbed mudstone samples in Nanning Basin as a typical argillaceous soft rock is chosen to the research object in this paper. The laboratory simulated destructive tests and the creep tests of full grouted anchor rod have been down. Through the destructive tests of mudstone sample, the instantaneous adhesive strength between the anchor body and mudstone in Nanning Basin is 70kPa. By analyzing the creep curves of anchor rod, a conclusion is that there is a long-term adhesive strength of anchor rod in argillaceous soft rock. When the design adhesive strength of anchor rod is less than the long-term adhesive strength, eventually the anchor rod is stable during the process of long-term pull-out. When the design adhesive strength of anchor rod is greater than the value, the creep of anchor rod with the time will do not stop until the anchor rod failure. The greater difference value between the instantaneous and long-term adhesive strength, the faster the rate of creep, the faster the anchor rod failure. Finally, for the permanent support engineering design of anchor rod in argillaceous soft rock, the paper gives two principles, as follows: (1) the design of anchor rod in argillaceous soft rock must be determined according to the long-term adhesive strength. (2) by using variety of technical measures, the impact of various factors on the creep of anchor rod will be decreased.
In the past, when used the foundation coefficient to calculate the internal force of anti-slide pile, power series method is usually adopted. The deformation compatibility conditions and continuity conditions of sliding surface between non-anchoring section and anchoring section are exploited to determine the final result, causing the lengthy solution process and that there is no guarantee for the calculation accuracy. This paper uses the foundation coefficient method in the calculation of internal force of anti-slide pile and employs the “m-k” method with a more complicated up-down foundation structure to get the finite difference equation to determine the new-type deeply buried anti-slide pile displacement and internal force. Then the calculation on the internal force and displacement of the whole pile can be realized easily through the procedure method. Finally, this paper makes a contrastive analysis on the result of the finite difference method and finite element calculation through the case study. As long as the equal differential step length is small enough, the calculation accuracy can meet the demand of engineer design and the program graph processing result can optimize the design of anti-slide pile.
Swelling rock has the properties of swelling and creep. Researches on coupling between swelling and creep have not yet been carried out. The expansive Paleogene mudstone is used to laboratory uniaxial compression tests, to find the coupling regularity between swelling and creep under different initial water contents, influent modes and loading methods. For coupling, the creep curves show similar characteristic of non-coupling. The creep deformation increases obviously and the long-term strength decreases comparing with non-coupling. With increasing initial water content, the creep deformation increases for coupling. The creep deformation increases with the enlargement of water-absorption area during the coupling creep. For single-stage and multi-stage loading, the creep regularity is similar to non-coupling. The sample will have a permanent residual deformation when unloaded at the second stable creep stage. The long-term strength of swelling rock is greater than the swelling pressure and the long-term strength is lower than that of non-coupling.
Due to the complexity of underground engineering, study on creep characteristics of surrounding rock mainly adopts laboratory simulation experiment. Recently, the similar materials are used to do the experiment both at home and abroad, yet it can't reflect the original nature and others of rock fissure in original rock mass. Through the field collection of undisturbed sample of Tertiary mudstone, the conclusions are made by laboratory model test on surrounding rock of underground tunnel and creep process regularity and failure mechanism in the surrounding rock in this paper as follows: there are three obvious stages of creep under certain stress levels, which is measured on the surface of surrounding rock mass in argillaceous soft rock tunnel--decay creep ,steady creep and accelerated creep. The surrounding rock will produce the accelerated creep damage when the stress level is over a threshold value. Creep damage of surrounding rock mainly includes the forms of roof sinking, floor working up, and forming a macro- fracture surfaces etc. Test results showed that the undisturbed surrounding rock fracture would be dissimilar to the homogeneous surrounding rock without fracture in damage model, and original fissure have a larger effect on creep damage of surrounding rock.
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