| In recent years,underground engineering,mine tunnel and slope engineering have developed rapidly,a large number of engineering problems about expansive rock began to emerge.The expansive rock is a special rock like rock and non-rock,which is similar to soil and soil.The expansive rock contains a large number of hydrophilic minerals,such as montmorillonite,illite,kaolinite,etc.These minerals have strong hydrophilicity,which causes the expansive rock to have the characteristics of water swelling and water shrinkage.It is precisely because of the characteristics of the expansive rock that it has brought many problems to the engineering of the expansive rock area,which has brought great problems to the researchers.The expansive rocks are widely distributed in China,and have different degrees of distribution in subtropical climate regions of China.The extensiveness of the expansive rock to the project and its extensive distribution make it impossible to study the expansive rock.This paper uses the expansive rock in the Xixiangtang area of Nanning,Guangxi.Basic physical and mechanical tests and expansion characteristics tests were carried out on the original rock samples,such as shear test,density test,water content test,free expansion rate test,dry saturated water absorption test and expansion force test.The intact expansive rock samples were air-dried and crushed to prepare the remolded samples with different water content.The direct shear test and lateral compression test were carried out on the remolded samples.In order to carry out further research on expansive rock,weak expansive rock,bentonite,lime and water are used as similar materials for expansive rock,and the index of expansion is determined by the free expansion rate,dry saturated water absorption,expansion force and volume expansion.Sixteen sets of proportioning schemes were designed by orthogonal test method,and the sixteen groups of similar materials were tested for expansion characteristics.The test results were analyzed and compared using the range method and the comprehensive equilibrium analysis method,and the optimal test group for each expansion similar material was obtained.Based on the deformation characteristics of expansive rocks,the improved four common growth curve models were validated by using nine sets of stress-displacement curve data under different water content conditions,which broadened the scope of application of the improved model.According to the characteristics of subtropical monsoon climate,the effects of temperature and humidityand temperature and humidity cycle on creep deformation of expansive rock are considered.Based on the Nishihara model,the humidity effect and temperature effect are introduced to establish a creep model considering the effects of humidity and temperature.The improved model will provide a new idea for the construction of the expansive rock creep model and lay the foundation for the accurate calculation of engineering design in the subtropical region.After the above tests,the results show that:(1)The expansive rock in the Xixiangtang area of Nanning,Guangxi,is weakly expansive.The pore ratio of the expansive rock increases gradually with the increase of water content,while the cohesion,internal friction angle and compressive modulus decrease with the increase of water content;The compressive modulus of the expansive rock increases with the increase of pressure,and the void ratio decreases with the increase of pressure.(2)Weak expansive rock,bentonite,lime,and water as raw materials can basically satisfy the expansion properties of similar materials of expansive rock.The free expansion ratio,dry saturated water absorption,expansion force and body expansion of similar proportion materials are mainly affected by factor A(Rock rubber ratio),while factors B(cement ratio)and C(water content)are secondary effects.(3)Through the comprehensive analysis and comparison of the test results of similar material proportion,it is concluded that the optimum group of medium expansibility similar material proportion is the fourth group.The comprehensive balance method was used to further analyze the test results,and the optimal combination of the ratio of strong expansion similar materials was A3B3C4,which is the 11 th group of the experimental scheme.(4)It is found that the correlation coefficients of the improved four curve models are improved.It is verified again that the improved Weibull model has the highest correlation coefficient,and the improved Richards model has the lowest correlation coefficient.(5)Based on the Nishihara model,a creep model considering the effects of temperature and humidity was constructed by preliminary derivation of the creep model. |
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