A STATIC STRESS ANALYSIS OF THE EFFECT OF STRATIFICATION PLANE OF ROCK MASSES ON SMOOTH BLASTING

The influenfial factors of stratification plane to smooth blasting are studied according to the ti eory of smooth blasting and the anslysis of static stress. The results show that the angle p between the maximum principal plane and the rertical line of stratification plane has some influence on the fracture of rock masses.     

THEORY AND PRACTICE OF SMOOTH BLASTING

A practical technique of smooth blasting in the formation rocks at qinjina coal mine in this paper is introduced. Based on the principal of smooth blasting, the relation between charge concentration, charge structure, spacing, discoincidence coefficient and coefficient of closely holes is respectively discussed. According to the theory of rock mechanics, the applied condilions is analysed.     

Analysis on the influence from rectangle cavity behind the lining to the primary support of tunnel

In process of the tunnel construction throw New Austrian Tunnelling Method, the result of smoothwall blasting to rock tunnel is not good, there are more and more cavities produced behind the lining. On the basis of engineering project, this paper makes the three-dimensional elastic-plastic analysis throw numerical simulation, discusses the stress-strain behavior of primary support when there is a different size of rectangle cavity behind the lining. In addition the safety factor of tunnel is calculated with cavity based on the strength reduction finit element method. This factor is compared with the factor of health tunnel. The stability of tunnel structure system is estimated through the linear regression analysis between stress of lining and safety factor.     

Smooth blasting design and optimization of large spanurban highway tunnels

Vibration resistance can be incorporated into blasting designs to avoid damages caused by the excavation of large span tunnels in busy urban areas, but only by basing excavation design schemes on actual situations. In view of the actual situation in the Jahua tunnel in Chongqing, P. R. China, research was conducted to identify a relevant explosion scheme. The research was based on theoretical analysis and in situ testing. Face step excavation was considered in the broadening band A, and upper drift excavation was adopted in broadening bands B, C, D and E. We simultaneously proposed selection criteria for smooth blasting parameters and the construction layout of broadening band B. Based on a regression analysis of the blasting vibration monitoring results, a spread orderliness of blasting vibration was drawn. Explosion parameters optimization measures were put forward, selected from the maximum charge quantity, millisecond blasting, reasonable blasting time difference, and the excavation plan. Field testing achieved satisfactory results. These findings will play an important role in guiding excavation blasting construction of tunnel projects and assuring the safety of ground buildings.     

Influence of blasting vibration on adjacent buildings of station tunnel

The influence of blasting vibration on the adjacent buildings is inevitable if blasting is employed for excavation. Daping station tunnel of Chongqing light railway project, on which there is dense with population and buildings, has a minimum buried depth of only four meters and maximum span length of 26.3 meters. The stepped excavation mode with short hole, multi round and V shaped cut are adopted. The maximum charge weight of one delayed interval is determined by the permitted vibration velocity. The smooth blasting technology with adding vibration reduction holes is used. Meanwhile, the charge weight per hole is strictly controlled. With the simulation and on site test, it is found that the proposed technology for tunnel construction is feasible.     

The Mechanism of Smooth and Pre-Cracking Blasting

The paper discusses some main factors of the mecha nism of smooth and pre-cracking blasting.The results of theoretical analyses show that the formation of directional cracks isrelated to the distan ce of holes.the quasi-static pressure and the strueture of rock mass. This paperalso studies the relation of len gth of crack and distance of holes.The initial cracks occur on the wallof holes instead of in the middle of two holes.     

Experiment Research of Pre-splitting in Bedded Composite Cutting Blasting Digging

The rock property difference of bedded composite rock often does not lead to ideal Pre-splitting blasting effect. The influence factor of Pre-splitting such as the dynamite quantity and explosive structure was studied by experiment with transient dynamic strain gauge testing system. At the same time, the damaged rock reduced by blasting was examined with RS-STOIC ultrasonic gauge. The results indicate that different dynamite densities are taken for considering especially property of bedded composite rock. The conclusion for cite.     

Research on Control and Safety Analysis in Demolition Blasting of Tower Buildings

In this paper,integrating the principium of demolition blasting of buildings and the practice,the general mechanism and affection factors of blasting harms such as blasting shock,collapsing shock,blasting rock,blasting shock wave and blasting noises produced in demolition blasting of buildings are analyzed.The safety problems existed in demolition blasting of buildings are discussed from three aspects such as the unsafe behavior of "person",the unsafe state of "substance"and the unsafe condition of "environment".Based on an engineering example,the difficulty of safety blasting of engineering example was analyzed,on this basis,corresponding effective safety defending measures and the method of safety control are brought forward.This study is significant to the construction safety and control of demolition blasting of similarity tower building in practice.     

Testing and modeling studies on creep characters of supports for tunnel using nonlinear constitutive model

Creep characters of tunnel supports structure is analyzed according to triaxial creep test of concrete specimen of deep tunnel supports structure adopting MTS815 hydraulic servo system. The creep parameters of nonlinear creep model are presented based oncreep curve. The finite element numerical model has been established considering tunnel construction process, creep characters of surrounding rock and support structure. The displacement characteristics, the effective stress and the maximum shear stress in different position in primary support and second lining are obtained through creep characters analysis of surrounding rock and supports structure. The features of displacement and stress dependent time of tunnel supports has visible difference comparing with discard creep effect and calculation displacement and practical monitoring results is basic concordance. The creep characters of surrounding rock and tunnel supports should be considered for deep tunnel.     

The Method on Surrounding Rock Classification for Highway Tunnel Construction Period in The Karst Areas of South China

Through the statistical analysis of analyzed the particularity of karst surrounding rock classification, finally obtained the rock classification index system of south karst highway tunnel construction based on rock strength, rock complete coefficient ,groundwater state, structural plane state the structural plane strike to tunnel influence, karst development to tunnel influence. And the model is applied to tianshengqiao tunnel and guanshang 2 tunnel with the example verification, and compared with the classification results and experts judgment to get the accuracy is 93.3%.     

Load Calculation Method of Shallow Tunnel under Unsymmetrical Loadings in Broken Surrounding Rock

Tunnel portal section mostly faces unfavorable geologic and topographical conditions, such as broken surrounding rock, shallow and unsymmetrical loadings. The current Chinese code for design of road tunnel provides the load calculation method of tunnel under unsymmetrical. However, according to the mechanic and deformation characteristics of the tunnel lining on site, the assumption is not suitable for the shallow tunnel under unsymmetrical loadings in broken surrounding rock. Therefore, through engineering case analysis and results of three-dimensional numerical analysis, the failure mechanism of shallow tunnel under unsymmetrical loadings in broken surrounding rock is presented firstly, that is, deep buried side broken surrounding rocks slump down after excavation and squeeze the lining, which makes the lining deform outward and bear passive earth pressure. Through the failure mechanism, the surrounding rock mainly includes slumping area and passive area. Then the corresponding formulas are deduced based on limit equilibrium theory. Finally, a case study is adopted to verify the feasibility of the new method. It is show that the new method is more reasonable than the method of current code.     

节理岩体中连拱隧道施工对周边建筑物的影响

以重庆东水门大桥—千厮门大桥渝中区连接隧道为研究对象,基于UDEC软件建立离散元数值模拟分析模型,研究了城区连拱隧道施工引起的地表沉降,上部建筑物基础沉降及倾斜,新建隧道下方已有轨道六号线的变形、受力特征,并将监测数据与数值模拟进行对比分析。结果表明,连拱隧道左侧隧道上导坑施工引起的隧道拱顶沉降和基础沉降量最大,经计算上部建筑物基础最大沉降量为3.81 mm,最大倾斜量为0.02%,建筑物基础沉降量和倾斜在规范许可范围之内;隧道施工引起的地层损失使得轨道六号线左拱肩向上隆起,六号线弯矩分布规律和其变形形态基本一致,弯矩最大值位于左拱肩部位,最大值为238 kN·m;数值模拟计算结果与监测数据量值相当,变形趋势基本一致;采用UDEC软件可以准确地计算出隧道开挖过程中节理的存在对隧道周围建筑物变形的影响。     

Development of Investigation on the V-notched Rock Blasting

A brief review on the origin of V-notched blasting and its application in engineering is given. A study on the fracturing mechanism and stress intensity factor at the tip of V-notch and parameter of the V-notched rock blasting is introduced based on reference given in this paper. It represents an idea of spiral V-notched blasting at last.     

The Application of Pre-splitting Blasting to Excavation on High Slope in Soft Rock Section

Based on analyzing about blasting mode of slope in the construction of road, the paper shows that pre splitting blasting is mostly suitable in the section of severely weathering soft rock with developed joints and fractures, introduced the laying out about the hole of pre splitting blasting that can apply in the high slope of the expressway in the section, and designed the parameter. The practice shows that it gained favourable effect by this method.     

Kolmogorov entropy analysis of surrounding rock system in the processing of unloading for deep buried tunnels

Rock is a kind of physical nonlinear complicated medium, under deep buried condition the surrounding rock system deformation shows geometrical nonlinear characteristic, and the interaction between the two nonlinear mechanism makes the unloading of surrounding rock system evolving complexly. Based on the Lagrangian method and large deformation caculation method, both the double nonlinearity and nonlinear dynamics character of deep buried tunnel surrounding rock system under unloading are studied. The numerical model results show that the Kolmogorov entropy has been extracted from the evolution data in the unloading process of surrounding rock system. The analysis indicates that the typical chaos character has been demonstrated in the process of unloading for deep buried tunnel surrounding system and the rock mass energy dissipation is analyzed at the stage of unloading.     

Analysis of Solid Fluid Coupling for Tunnel Excavation in Complicated Fractured Rock Masses

When tunnels are through water bearing section of fractured rock mass, a complex interaction process between rock mass deformation and fluid transportation is one of the most important reasons for water gushing, water bursting and mud bursting.To study the rock mass deformation and fluid transportation in tunnel excavation under complex geological conditions, a hydraulic model of complex crack rock mass was established from the relationship between the crack growth degree of surrounding rock in deep buried tunnel and the engineering scale, with which fracture network of different levels in rock mass could be considered simultaneously.Furthermore,a computer Fortran program was put forward to simulate the solid fluid coupling of excavation process of a deep buried tunnel.And it was found that the principal fractures had strong flowing action and network fractures had storage function and lag effect in seepage area.And the yield area of surrounding rock was increased under the coupling of seepage field and stress field.     

MODEL TEST RESEARCH ON A COMPOSITE LINING OF UNDERGROUND ENGINEERING IN JOINTED ROCK

Combined with thedesign precept of Cai-Yuan highway tunnel 2 in Chongqing,stress state,time ffectiveness and rupture mechanism of rock near the bounda-ries of the tunnel and the second lining in jointed rock mass arc studied with model tests.The results show that shotcretc-bolt support betters mechanical properties of the periphey rock of the tunnel,and increases the capacity of anti-deformation.The second lining also has the action of supporting structure.     

The Monitoring Measurements and Country Rock Control of NATM in Tunnel of Express Road during Construction

In this paper the author' s study on the monitoring measurement technique of NATM,the regularity and conditions of the country rock deformation are analysed based on the site measurement data in the west section of Zhongliangshan tunnel. The regression analysis of measure data for different measure lines of vavious country rock is done by the use of self-compiled CRAP program. The stability criterion for various rockmass and optimum time for primary and permanent support are provided. The conclusion available could conduct the theoretical research of NATM deeply as well as tunnel design and construction.     

Experimental Study on Construction Method of Super-Large Section Tunnel

For the super-large section tunnel due to its super large span and flatness,together with the effect of various processes and excitation of surrounding rock during construction,the mechanical behavior of super-large section tunnel is quite complicated.Making use of the "CTSSSRH",the physical analogue for simulating the construction dynamic process of super-large section tunnel in different construction methods is experimented.The rule of surrounding rock displacement and strain development is studied and the reasonable construction method is put forward.