| The Dongting Lake area is located south of the middle reaches of the Yangtze River and has a vast territory.In order to promote the economic development of this region,a large number of highways and urban roads need to be built.However,the soft soil in the Dongting Lake area seriously affects the stability of the road and limits the economic development and construction in this area.For soft ground,multi-bag inflatable anchor has the ability to strengthen quickly and provide large anchorage force;since multi-bag inflatable anchor can be recycled,it also has the advantages of economy and environmental protection.Therefore,multi-bag inflatable anchors are considered for reinforcement of soft soil in Dongting Lake area.In this thesis,the mechanical properties of the soil were firstly determined by indoor geotechnical tests and triaxial tests under various conditions,and the intrinsic model of soft soil in Dongting Lake area was proposed,then the indoor model tests were carried out,and pullout tests were conducted on single and multiple anchors under different working conditions,and finally the numerical simulation method was used to simulate the pullout tests of inflatable anchors to verify and propose the three-damage factor damage theory to construct the ultimate pullout capacity calculation equation The main research contents and results are as follows.(1)Through indoor geotechnical tests and triaxial tests under various conditions on soft soils in Dongting Lake area,the mechanical properties of the soil,as well as the stress-strain relationship,internal friction angle and cohesion under different conditions were determined.(2)Based on the test results of CU test and CD test,a three-damage factor intrinsic model that can describe the stress-strain relationship of both tests is established and the relevant parameters are analyzed.(3)The pullout test of single multi-capsule inflatable anchor was carried out under different conditions to determine that the water content is the key factor affecting the ultimate pullout capacity of soft soil in the Dongting Lake area;under the condition that the water content exceeds the liquid limit,the increase of airbag pressure,anchor burial depth and airbag length has an optimization effect on the pullout resistance of anchor,and the increase of airbag hardness and airbag spacing has a deterioration effect on the pullout resistance of anchor.(4)The change law of group anchor effect coefficient of double anchor pullout test of multi-bag inflatable anchor under different water content was carried out,and it was found that the group anchor effect coefficient of double anchor spacing 20 cm was around 1 when the liquid limit was exceeded.(5)Numerical simulation software was used to simulate the pull-out test of multi-bag inflatable anchor,and the ultimate pull-out load capacity of multi-bag inflatable anchor was obtained;the three damage factors were introduced into the theory of circular hole expansion for formula derivation,and the formula of the ultimate pull-out load capacity considering damage was obtained;the three results were compared and analyzed to verify the applicability of the formula of the ultimate pull-out load considering damage. |
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