| Similar model test technique is widely used in underground geotechnical engineering model test due to its advantages of strong feasibility,wide application range,low test cost and so on.Because of the destructiveness or a lack of recoverability in experiment and that it's difficult to reappear the test target as to its actual size under laboratory conditions,a contractible model is made to replace the prototype as a common method.It's likely to conjecture experimental phenomena and results of the prototype on the basis of the physical and mechanical similarity between the prototype and the model,combined the experimental results of the model and principle of similitude.Similar model test is finally tested through a scale model.How to successfully make a scale model is the key to the success of the test.The result of the test is closely related to the material used in the model.To ensure that the physical and mechanical properties of the prototype and the model are similar,to find raw materials suitable for the models is the key to both making model and doing model test successfully.The thesis treats the cap rock of Da5 aquifer gas storage as research objective and preliminarily explores the materials can be used to the experiment of Da5's cap rock and its mixture ratio.In order to find out the change regulation of physical and mechanical properties(density,modulus of elasticity,uniaxial compressive strength and tensile strengt)with varieties of the ratio of aggregate's mass to cementing agent's,the ratio of cement's mass to gupse's,and the percentage of barite powder,we poured samples,did uniaxial compression experiment and brazil splitting experiment,gathered statistics and analysed test data.Furthermore,an improved brittleness evaluation index is built on the basis of summing up existing brittleness evaluation indexes.Combined the only stress-strain curve gained from Da5's cap rock and with the improved brittleness evaluation method applied to evaluate cap rock's brittleness,the following results are obtained in this paper:1.Similarity relation between similarity ratios is derived while combined principle of similitude and elastic-plastic mechanics.Similarity ratios between the prototype and model are confirmed while synthetically considering experimental conditions and target:similarity ratio of gravity isC_?=4.1,similarity ratio of geometry isC_l=30,similarity ratio of strength and modulus of elasticity isC_?=C_E=42.Raw materias being used to make model are aggregate and cementing agent.Aggregate includes coarse aggregate sand and fine aggregate barite powder while cementing agent includes cement and gypsum.The specific ratios of aggregate's mass to cementing agent's are 2:1,4:1,6:1,8:1,10:1,ratios of cement's mass to gupse's are 1:9,3:7,5:5,7:3,9:1,and the percentages of barite powder are 0,0.1,0.2,0.3,0.4.In order to pour standard cylindrical specimens for uniaxial compression experiment and brazil splitting experiment,mould is designed on our own and made;2.Twenty-five experiment groups in total are designed with the orthogonal experimental design method.We poured samples and did uniaxial compression experiment and brazil splitting experiment.The results show that density of similar material ranges from 1.68 gram per cubic centimeter to 1.95 gram per cubic centimeter,uniaxial compressive strength of similar material ranges from 0.26 MPa to 4.23MPa,modulus of elasticity of similar material ranges from 7.781 MPa to 322.222MPa,and tensile strength of similar material ranges from 0.0653 MPa to 0.8981 MPa.The similar material we made basically meets the requirements of Da5 aquifer gas storage's cap rock while compared with parameters of the objective model(density,uniaxial compressive strength,modulus of elasticity and tensile strengt of the model material are 1.79 gram per cubic centimeter,1.53MPa,150.40MPa and 0.13MPa);3.The change regulation of similar model material's physical and mechanical properties with the ratio of aggregate's mass to cementing agent's,the ratio of cement's mass to gupse's and the percentage of barite powder is explored in the paper.The test results show variation tendency of density,uniaxial compressive strength,modulus of elasticity and tensile strength has some relationship with the ratio of aggregate's mass to cementing agent's,the ratio of cement's mass to gupse's and the percentage of barite powder.Thereinto,the density decreases with the increase of the ratio of aggregate's mass to cementing agent's while increases with the increase of the ratio of cement's mass to gupse's and the percentage of barite powder;uniaxial compressive strength,modulus of elasticity and tensile strength all decreases with the increase of the ratio of aggregate's mass to cementing agent's,the ratio of cement's mass to gupse's and the percentage of barite powder.Thereinto the correlation of the ratio of aggregate's mass to cementing agent's is bigger than the ratio of cement's mass to gupse's and the percentage of barite powder's;4.An improved method for brittleness evaluation based on stress-strain curve is proposed.Its index establishing and calculation process is expatiated.The influence of relative size of stress drop after peak,absolute rate and yield stage are comprehensively taken into account in this method to make up for the deficiency of the existing evaluation methods.With the method applied to brittleness evaluation of uniaxial compression test of different rocks,three axis compression test of the same rock and Xing9's cap rock,its limitations,advantages and practicability are expatiated,and its applicability are illustrated while compared to other evaluation results.A conclusion that brittleness of Da5's cap rock is weaker namely plastic deformation capability is stronger under specific stratigraphic conditions is gained while applied the method into brittleness evaluation of Da5's cap rock.5.After the deduction of potential reservoir's pressure distribution and cap rock's deformation distribution during fluid injection process,abaqus was used to study the cap cork's bending deformation effect,contrast and analyze different parameters'effect on Mises stress,tension failure area and plastic yielding area.It shows that gas injection stages,displacement distribution forms and coefficients of horizontal pressure have a great effect on simulation's result while dilation angles,constitutive relations and element types have a lesser one. |
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