Excavation compensation theory and supplementary technology system for large deformation disasters

Given the challenges in managing large deformation disasters in energy engineering,traffic tunnel engineering,and slope engineering,the excavation compensation theory has been proposed for large deformation disasters and the supplementary technology system is developed accordingly.This theory is based on the concept that“all destructive behaviors in tunnel engineering originate from excavation.”This paper summarizes the development of the excavation compensation theory in five aspects:the“theory,”“equipment,”“technology,”the design method with large deformation mechanics,and engineering applications.First,the calculation method for compensation force has been developed based on this theory,and a comprehensive large deformation disaster control theory system is formed.Second,a negative Poisson's ratio anchor cable with high preload,large deformation,and super energy absorption characteristics has been independently developed and applied to large deformation disaster control.An intelligent tunnel monitoring and early warning cloud platform system are established for remote monitoring and early warning system of Newton force in landslide geological hazards.Third,the double gradient advance grouting technology,the two-dimensional blasting technology,and the integrated Newton force monitoring--early warning--control technology are developed for different engineering environments.Finally,some applications of this theory in China's energy,traffic tunnels,landslide,and other field projects have been analyzed,which successfully demonstrates the capability of this theory in large deformation disaster control.

Numerical simulation study on shear resistance of anchorage joints considering tensile-shear fracture criterion of 2G-NPR bolt

2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.

国际对比研究计划——面向地震预测的跨断层测量

An earthquake is one of the greatest natural disaster risks to human beings.With their unexpectedness and shockingly destructive power,earthquakes can cause major catastrophes to human society.According to the theory of plate tectonics,the lithosphere is divided into plates that move relative to each other,with most earthquakes worldwide occurring at the plates’junction.Statistically,more than 90% of natural earthquakes are due to seismogenic faults,which are caused by the relative motion of two plate blocks along the tectonic zone(i.e.,surfaces of the blocks).

Compensation excavation method control for large deformation disaster of mountain soft rock tunnel

In recent years,the mine tunneling method and the new Austrian tunneling method have been considered the main theories of tunneling approaches in China.It is difficult for the traditional technique to overcome the large deformation problems imposed by complex geological conditions of mountain soft rock tunneling.Hence,the compensation excavation method has been proposed to solve this issue under the consideration that all damage in tunneling originates from the excavation.It uses supportive strategies to counteract the excavation effects successfully.This paper provides an overview of the fundamental ideas of the compensation excavation method,methodologies,and field applications.The scientific validity and feasibility of the compensation excavation method were investigated through the practical engineering study of the Muzhailing and Changning tunnels.

Lateral damage mechanism of the double-track tunnel in the mountainous layered soft rock and NPR anchor cable control

Due to complex geological formations,lateral damage often occurs during excavation in mountainous layered soft rock double-track tunnels.This paper discusses the stresses and the damage characteristics of the surrounding rock under overload in a mountainous layered soft rock double-track tunnel through indoor model experiments to provide a basis for the effective control of lateral damage.The experiments show that the conventional support method cannot effectively control the lateral damage due to interlayer sliding.Therefore,the negative Poisson’s ratio(NPR)anchor/cable control method is proposed.And the scientificity and feasibility of the NPR anchor/cable control technology are proved by the field application and monitoring data of the Minxian Tunnel and Changning Tunnel.It is further demonstrated that high preload is the most effective way to control the lateral damage in layered soft rock tunnels.

State of the art review of the large deformation rock bolts

Rock bolting technique is an important reinforcement measure in the geotechnical engineering practice.New rock bolts have been continuously emerging through the development of rock supporting technology.Complex conditions,such as high crustal stress,extremely soft rock,and strong mining disturbance often occur in the deep mining,resulting in large deformation of the surrounding rock masses.Since the deformation of traditional rock bolts is generally below 200 mm,failure often occurs to the rock bolts because of insufficient deformability.To effectively control the large deformation of surrounding rock masses caused by complex conditions,it is necessary to develop large deformation rock bolts with high constant resistance,also called energy-absorbing bolts.This paper systematically reviews the development of large deformation rock bolts and the structure,energy absorption mechanism,anchorage performance,and mechanical properties of several typical large deformation rock bolts.The advantages and disadvantages of existing large deformation rock bolts are compared and the concept of constant resistance large deformation support is introduced.