| In most cases,karst caves,caverns and underground rivers are generated from carbonate rocks affected by the karst underground water.The hydro-chemical interaction has led to the dissolution of part of active minerals and cements between mineral grains in the rock mass,and correspondingly the solute diffused along with the water migration has changed the physico-mechanical properties of rock mass.The disturbance from the tunneling of karst tunnels and the underground construction,and the vibration of a running train,both have altered the degree and direction of water-rock interaction in carbonate rocks,which has an important influence on the deformation caused by dynamic disturbance and damage performance.The hydro-chemical corrosion of underground water has played a leading role during the process of expanding the gaps in the rock mass into the solution cracks and pipelines,at the early stage of occurrence and development of water burst in the karst tunnel.Moreover,the dynamic disturbance from the outside world will change the hydro-chemical corrosion effect,accelerating the development of solution cracks and pipelines,and then the physical destructive effects,such as the focused washout and corrosion,have led to the water burst.That is why a series of geological disasters happen and their developing process,such as the water burst and collapse of karst in the process of tunneling and underground construction.As a result,the study on the damage performance by the dynamic disturbance and hydro-chemical corrosion in the karst tunnel,as well as the mechanism of water burst in the filling karst cave,has been of great significance to the scientific evaluations on the long-term stability of rock mass mechanics.In the context of the offshore karst subway tunnel in Dalian,the article has taken karst carbonate rocks revealed by the tunnel excavation as the topic of study,by the study methods such as laboratory tests,theoretical analysis and numerical simulation,and the research focusing on "the issue of damage performance by the dynamic disturbance and hydro-chemical corrosion in the karst tunnel,as well as the mechanism of water burst in the filling karst cave" has been implemented.Firstly,the experiments on the damage performance and deformation characteristics by the dynamic disturbance and hydro-chemical corrosion of carbonate rocks are implemented,and in view of the formation and failure mechanism of karst,the research is to establish damage variables of the dynamic disturbance and chemical erosion by underground water.Secondly,based on the above-mentioned results,the damage model of dynamic disturbance and hydro-chemical corrosion is created,and the damage performance and deformation characteristics by the dynamic disturbance and hydro-chemical corrosion in the tunnel will be further studied in the case of numerical calculation.In the end,in the basis of the above research,a study of macro-model test is implemented aiming at the tunnel with filling karst cave,in order to reveal the phenomena and rules of water burst.From the meso-scopic mechanism created by the karst to the macroscopic model test of water burst of karst,based on the progressive ideology,the study on the damage performance by the dynamic disturbance to the karst tunnel surrounding rock and hydro-chemical corrosion,as well as the water burst in the filling karst cave is carried out.Here is how the specific researches are going:(1)The study on the deformation test of carbonate rocks in the effect of hydro-chemical corrosion at different periods of time is implemented,to obtain the variations of pH value in the process of soaking and the images of the test specimen under the SEM micro-scanning electron microscope,and hence various deformation characteristics and damage performances of test specimen by corrosion at different periods of time are achieved.Based on the test,the data-fitting of fatigue life prediction N-T curve of carbonate rocks by corrosion at different periods of time,could be applied for the prediction of fatigue life of carbonate rocks in the effect of dynamic disturbance and hydro-chemical corrosion.In the basis of the above-mentioned result,the damage variable of dynamic disturbance is established,and meanwhile that of hydro-chemical corrosion is defined by the voidage.On the theoretical basis of hydro-chemical dynamics,the damage model of hydro-chemical corrosion of rocks is created,and then the calculation of hydro-chemical damage is implemented.The definitions of damage variables of hydro-chemical corrosion and dynamic disturbance,as well as the establishment of the damage model of hydro-chemical corrosion,have laid the foundation for the future development of damage model of dynamic disturbance and hydro-chemical corrosion of rocks.(2)Consider the damage mechanism caused by the slippage of plastic deformation and the increase of micro-cracks of rocks resulted from the dynamic disturbance and hydro-chemical corrosion,and establish the elastic-plastic damage model on the basis of Mohr-Coulomb yield criterion.And the evolution law of damage variable of rocks is represented by the equivalent plastic strain.On the basis of Mohr-Coulomb constitutive integration algorithm,the Mohr-Coulomb implicit return mapping algorithm with principal stress space of elastic-plastic damage,which has deduced the three main procedures of flexible prediction,plastic correction and damage correction,solves the problem of "singularity" of the cusp with the principal stress space as a starting point.With the object-oriented programming method,the constitutive solver of RDM-C of elastic-plastic damage is written by C++.Based on the elastic-plastic damage model,the elastic-plastic dynamic solver is written by the Newmark-? method.(3)The damage model of dynamic disturbance and hydro-chemical corrosion of rocks,is created by the damage variables of dynamic disturbance and hydro-chemical corrosion of rocks which are established on the results of laboratory tests.With the anisotropic percolation procedure written by the percolation theory,integrated with the above-mentioned dynamic solver of elastic-plastic damage,anisotropic percolation procedure and PHREEQC,the calculation procedure of hydro-geochemistry,the C++language is applied for the development of DPGC,the solver of damage model affected by the dynamic disturbance and hydro-chemical corrosion of carbonate rocks,to reveal the damage performance of dynamic disturbance and hydro-chemical corrosion of carbonate rocks.(4)The loading system of fluid-structure interaction model test of the tunnel is developed,to make an analysis of the performance of testing system,and deformation and stress condition under construction.On the basis of the similar theory of materials and the loading system of model test,the model test and study on the progressive failure of Yong'an tunneling works in Dalian is implemented,meticulously analyzing the crack growth process until the destruction when the tunnel is excavated in the soft formation of the relatively competent formation,in order to reveal the crack growth and damage mechanism of surrounding rock in the tunneling,and also to reflect the feasibility and practicability of the model test system.(5)Based on the above-mentioned study of(4),the similar non-hydrophilic fluid-structure interaction materials with the gypsum and cement as the cementing agents,the tailing sand and rubber powder as the aggregates,the iron powder and bentonite as the modifiers,have been further developed.The study on the water burst model test specific to the tunnel with filling karst cave from Dongwei Road to Chunguang Street of Dalian Metro Line No.1 has been implemented. |
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