Abstract
With the improvement of the line level,tunnels will inevitably develop towards the direction of"deep,long,and large",and the characteristics of"deep,long,and large"significantly increase the risk of large deformation of high stress weak surrounding rock.Since the first large-scale deformation of soft rock occurred in the early 20th century,this problem has been a difficult problem for tunnel engineering design and construction.Tunnel technology workers generally use scientific logical thinking methods to conduct research on this issue.This study adopts dialectical thinking to philosophically reflect on the problem of large deformation of weak surrounding rock from the aspects of the essence,prediction,support concept,and technology of large deformation.It provides a new perspective for dealing with the problem of large deformation of high stress weak surrounding rock and enhances the wisdom and art of dealing with this problem.
The International Society of Rock Mechanics refers to high stress soft rock deformation as"compression type deformation",which occurs due to high ground stress as the external cause and low strength,low modulus,and high rheological properties of the surrounding rock as the internal cause.The mechanism of occurrence is the shear creep caused by the shear stress in the rock mass exceeding the shear strength,which continuously expands the loose zone and plastic zone to the deeper part.The essence of large deformation is the large displacement of the tunnel wall caused by the deformation of the surrounding rock itself,which occurs under the contradictory action of external factors represented by high ground stress and internal factors represented by the properties of the surrounding rock itself.This large displacement exhibits a significant time cumulative effect.
The prediction of large deformation of surrounding rock should adhere to the principle of focusing on the intrinsic properties of the surrounding rock itself,supplemented by external factors such as geostress,groundwater,and geological structure.Based on the obtained geological exploration data and the type of geostress field,formation lithology,and geological structure,the first step is to determine whether large deformation prediction should be carried out.Then,the preliminary judgment of large deformation should be made based on the exploration data in the design stage,and the detailed judgment of large deformation should be made based on the more detailed internal and external factors revealed in the construction stage.
Hegel pointed out that the task of philosophy is to follow human knowledge,engage in repeated thinking,and grasp the dialectical historical development of human knowledge.Using the methodology of dialectical principles of internal and external factors,this study analyzes the evolution of the concept and technology of tunnel support in mining methods.It is found that from emphasizing passive support structures as the external factor,to continuously valuing the role of surrounding rock as the internal factor,to adhering to the combination of internal and external factors,and being able to flexibly balance the strengths of both parties and exchange their positions.When the strength of the external factor is greater than that of the internal factor,the external factor plays a decisive role,and vice versa.The above rules of understanding are also in line with the current scholars're understanding of the relationship between internal and external factors.
Large deformations can be divided into general large deformations and severe large deformations.The essential difference lies in the fact that although the plastic zone of large deformations continues to develop deeper,it can eventually self stabilize under unsupported conditions,even though the deformation of the surrounding rock has exceeded the normal reserved value.The plastic zone of severe large deformation continues to develop deeper,and the final deformation does not converge under unsupported conditions.For general large deformations,the fundamental role of surrounding rock as the internal cause should always be emphasized.The concept of"resistance"should be reflected through timely and strong support,which is always committed to protection,early reinforcement of surrounding rock,and ultimately using surrounding rock and initial support to jointly bear the pressure of surrounding rock and control its deformation.In response to severe and large deformations,we should adhere to the combination of internal and external factors,and flexibly grasp the transformation of internal and external factors.The concept of"release"should be reflected through measures such as advanced guide holes and pressure support structures.However,this"release"is to better"resist",so it is essentially the concept of"combination of resistance and release".The design concept of"combining resistance and release"focuses on the external factor of geostress as the main contradiction,aiming to reasonably release the strain energy caused by high geostress,but at the same time,the role of surrounding rock as the internal factor cannot be ignored.With timely and proactive support,the displacement of the surrounding rock and the expansion of the plastic zone can be effectively controlled after excavation,thereby reducing the surrounding rock pressure acting on the support structure;It is also possible to quickly reinforce the loose ring into a load-bearing arch,improve the resistance of the surrounding rock,and consume strain energy together with the yielding support structure.关键词
高地应力/软弱围岩/大变形/哲学思考Key words
high ground stress/weak surrounding rock/large deformation/philosophizing分类
交通运输
