Study On Water-Rock Mechanism And Time-Dependent Deformation Characteristics Of Red Beds Soft Rock In Central Yunnan

The soft rock of red beds in central Yunnan mainly refers to mudstone,silty mudstone and other mudstones.This kind of rock often shows poor engineering geological characteristics because of its poor diagenesis and the with abundant mud inside:(1).The strength is low,so it shows poor anti-sliding ability and bearing capacity in practical engineering;(2).The deformation modulus is small,and it is easy to produce large deformation.In practical engineering,it shows that,the surrounding rock of the tunnel has large deformation,and the foundation is prone to settlement and deformation.(3).The rheological effect is obvious,and the long-term strength is generally 70% of the uniaxial compressive strength.If this characteristic is not fully considered in engineering practice,it may eventually affect the long-term operation of the project.(4).The engineering geological characteristics of rocks will be strongly influenced by water-rock interaction,which will then affect the construction difficulty and Engineering operation stability of the project.However,there is no systematic study on the water-rock interaction mechanism of Red Beds Soft Rock in central Yunnan,and there is no systematic study on the time-dependent deformation characteristics of red beds in central Yunnan which affected by water-rock interaction.Based on this,this paper intends to study the water-rock mechanism of the red beds in central Yunnan,explain the influence degree of water-rock interaction on the Red Beds Soft Rocks in central Yunnan and its influencing factors in theory,and then study the characteristics of water-rock interaction on the time-dependent deformation of rocks,so as to provide guidance for engineering construction and operation in the red beds area in central Yunnan.This paper intends to systematically study the water-rock mechanism and time-dependent deformation characteristics of Red Beds Soft Rock in central Yunnan from the following aspects:1.The basic main strata and lithology of Red Beds Soft Rock in central Yunnan.The sedimentary facies of the red beds in central Yunnan are mostly shallow lacustrine facies near the center of the basin,such as Zhanghe Formation,Puchanghe Formation and Tuodian Formation in the western part of Yunnan Province.With the gradual excess of the sedimentary environment to shallow lake facies or fluvial facies,the content of soft rocks will become less and less,and finally become over-hard or hard rocks such as sandstone with mudstone or whole sandstone.Such sedimentary environment resulted in the main lithology of Red Beds Soft Rocks in central Yunnan,which mainly consisted of mudstone or silty mudstone and other argillaceous rocks.2.To study on the main mineral composition of Red Beds Soft Rock in central Yunnan and the main engineering characteristics of Red Beds Soft rock.Rock properties are mainly controlled by mineral composition and rock structure.By studying the mineral composition and engineering geological characteristics of Red Beds Soft Rock in central Yunnan,the composition,physical and mechanical properties and deformation characteristics of red beds soft rock are obtained,which lays a foundation for studying the engineering geological characteristics of Red Beds Soft Rock caused by water-rock interaction.3.To study on the water-rock interaction manifestations of Red Beds Soft Rocks in central Yunnan.By studying the water-rock characteristics of Red Beds Soft Rock in central Yunnan,it is concluded that the main characteristics of Red Beds Soft Rock in central Yunnan are rock disintegration,rock expansion and rock softening.On this basis,the grading of the water-rock severity of the red beds soft rock in the middle Yunnan is studied.By studying the intensity of soft rock water-rock interaction in red beds,the judgement can be made,and then according to the intensity of soft rock water-rock interaction,the design,construction and operation of this kind of rock area can be guided to a certain extent.4.The disintegration classification standard of Red Beds Soft Rock in central Yunnan is studied.Previous classification criteria for slake ability only considered whether soft rock slaked or not.And the process of slake did not take into consideration systematically.Also,the speed of slake and the degree of disintegration is not considered.In this paper,the disintegration rate,disintegration degree and disintegration time effect of soft rock are comprehensively considered by revising the classification standard recommended by ISRM.Finally,a set of disintegration resistance classification standard suitable for Red Beds Soft Rock Area in central Yunnan is obtained.5.The expansibility classification standard of Red Beds Soft Rock in central Yunnan is studied.Previous classification criteria for rock expansibility are mostly indirect and deformation indicators,which can not provide a good reference for engineering design and construction.Based on these classification indicators,this paper introduces expansive force indicators for soft rock.As a direct index of expansibility,expansive force can well reflect the expansive characteristics of rock,and can be well optimized and constructed according to the magnitude of expansive force.6.The long-term softening effect of red beds in central Yunnan is studied.Previous studies on the softening of red beds in central Yunnan have only focused on the softening coefficient of rocks,without considering the time effect of water-rock interaction.As the surrounding rock of the water diversion tunnel in the red beds area of central Yunnan,the Red Beds Soft Rock is bound to be in a long-term saturated environment,so it is not enough to consider the softening effect of rock closely.Based on this,this paper innovatively studies the time effect of softening of the Red Beds Soft Rock in Central Yunnan,and obtains the changing law of strength of the Red Beds Soft Rock under the long-term saturated effect,which is closely combined with the engineering practice.7.The influencing factors of water-rock interaction of red beds in central Yunnan are studied.Previously,the influencing factors of rock water-rock interaction were studied separately according to the different manifestations of water-rock interaction,and the influencing factors of water-rock interaction were not considered systematically.In this paper,the water-rock interaction of red beds in central Yunnan is considered as a system for the first time,and the essence of water-rock interaction of red beds in central Yunnan is the change of porosity in rocks.When the porosity of rocks increases,the soft rocks of red beds in central Yunnan mainly show the characteristics of softening and swelling,and when the increase of porosity in rocks exceeds the limit,the rocks show the characteristics of softening and swelling.The main factors affecting the change of rock porosity are the mineral composition of rock and the structure of rock itself.8.The relationship between water-rock properties in central Yunnan is studied.Previous studies have focused on the water-rock characteristics of rocks themselves,without considering the relationship between water-rock characteristics.By studying the correlation between water-rock properties of red beds in central Yunnan,therelationship between water-rock properties of red beds in central Yunnan is obtained.The softening and expansibility of red beds in central Yunnan belong to the development stage of water-rock interaction.At this stage,the connection of water-rock interaction-like rocks decreases and the porosity increases,which makes the strength of rocks decrease and show the softening of rocks.At the same time,the swelling of clay minerals in rocks and the expansion of water filling in cracks make the volume of rocks swell.When the connecting force in rocks can not overcome the swelling pressure of rocks,the rocks break up,showing disintegration,that is,the disintegration of rocks is the final form of water-rock interaction of red beds in central Yunnan.9.The long-term saturated strength of Red Beds Soft Rock in central Yunnan is studied.Previous studies on the long-term saturated strength of Red Beds Soft Rock in central Yunnan remain on the rheological effect under natural conditions,but have not studied the rheological characteristics under saturated water,because soft rock is easy to disintegrate and it is difficult to study its saturated water.In order to overcome this difficulty,the long-term saturated rheology of Red Beds Soft Rocks in central Yunnan is studied.The long-term saturated strength and constitutive relationship of Red Beds Soft Rocks in central Yunnan are obtained for the first time,which lays a foundation for further research.