Research on Test of Reducing Deformation of Soft Rock Tunnel with High Stress Level by Pilot Heading

2012 ◽  
Vol 170-173 ◽  
pp. 1565-1568
Author(s):  
Xin Yan ◽  
Yang Sheng Ye
Keyword(s):  
High Stress ◽  
Soft Rock ◽  
Primary Reinforcement ◽  
Geological Exploration ◽  
Ventilation Condition ◽  
Ground Stress ◽  
High Stress Level ◽  
Rock Tunnel ◽  
Primary Support ◽  
Surrounding Rock Deformation

Generally speaking, the pilot heading is aways used for geological exploration，speeding up the construction，improving the draining and Ventilation condition, promoting efficiency of residue transporting. When tunneling on high ground stress soft rock region，the pilot heading will play a more important role. Lan yu line Mu Zhai ling tunnel main passes through the region of carbonaceous slate. Due to the high ground stresses, the primary reinforcement system underwent large deformation, evenmore the lining is cracked. Through excaving the pilot heading, can relief the stress. Then enlarg the pilot heading to main tunnel, the deformation of primary support will be reduced, and the tunnel will be stable. Compare the "pilot and enlarging" excavation method with bench excavation method on surrounding rock deformation. As the result, the "pilot and enlarging" excavation method is effective for control of the deformation of the tunnel.

Comparison and Analysis of Different Excavation Methods in Soft Rock-Extremely Soft Rock Tunnel

2012 ◽  
Vol 256-259 ◽  
pp. 1201-1205
Author(s):  
Xiang Dong Zhang ◽  
Peng Tao Zhao ◽  
Wen Jun Gu
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Maximum Difference ◽  
Tunnel Excavation ◽  
Comparison And Analysis ◽  
Rock Tunnel ◽  
Complex Geology ◽  
Surrounding Rock Deformation ◽  
Excavation Methods

In order to further study the law of surrounding rock deformation of soft rock-extremely soft rock double arch tunnel, resolve problem of tunnel excavation in complex geology conditions, based on project example, the central heading full section, central heading step and division method (three heading method) as research object, measured and simulated results were compared and analyzed, and used ANDIA software to do dynamic simulation. The results show that the characters of surrounding rock deformation are different with different excavation methods; Simulated and measured results are almost the same ,and the maximum difference has only 6%, reflecting simulated value has a certain reliability; The more the step numbers are excavated in soft rock-extremely soft rock tunnel, the smaller the area excavated is, the smaller the rock is disturbance, the smaller the surface subsidence and two state convergence value is, more be able to meet construction requirements; Compared with the other two methods, division method is more to reduce the deformation in the surrounding rock with class of V.

Numerical Analysis for Thermal-Chemical-Stress Coupling in Deep Rock Creep Properties

2013 ◽  
Vol 561 ◽  
pp. 657-662
Author(s):  
Yan Chun Wang ◽  
Yuan Li ◽  
Jian Guang Li
Keyword(s):  
Ph Value ◽  
Coupling Effect ◽  
High Stress ◽  
Soft Rock ◽  
Effect Of Temperature ◽  
Creep Equation ◽  
Creep Properties ◽  
Rock Creep ◽  
Deep Rock ◽  
Rock Tunnel

The control equations for analyzing coupled thermal chemical-mechanical phenomena of deep rocks are established. Using creep equation by experimental data, 3D numerical simulation for creep properties of deep soft tunnel under coupling effect of temperature field, chemical field and stress field are conducted by ANSYS, and different effects of these fields on deep soft rock tunnel creep properties are analyzed, whats more time-creep curves of different temperature, pH value and stress deviation of the mid-point of the top of tunnel are obtained. Effect of these three fields on creep characteristics of deep soft rock cant be ignored. Under deep complex environment, high-stress is main factor of tunnel creep; creep increasing with temperature increasing. From simulation results, we get whether acidic environment or alkaline environment causes significantly stronger corrosive effect on the rock mass than the neutral environment, and increases its creep.

Analysis of Soft Rock Tunnel Mechanics Effects Based on Strain Softening Model of Surrounding Rock

2012 ◽  
Vol 424-425 ◽  
pp. 520-525
Author(s):  
Jie Hong Zhang
Keyword(s):  
Numerical Analysis ◽  
Strain Softening ◽  
Mechanical Response ◽  
High Stress ◽  
Soft Rock ◽  
Mechanical Effect ◽  
Surrounding Rock ◽  
Plastic Range ◽  
Construction Design ◽  
Rock Tunnel

Aiming at mechanical response of soft surrounding tunnel affected by high stress, the mechanical effect in the process of excavation and supporting of surrounding rockmass was analyzed by softening model. First of all, mechanics properties of soft surrounding rock and strain softening model have been discussed. Then, based on strain softening model, numerical analysis was carried out, and stress and displacement field, plastic range in the in the process of excavation and supporting was obtained. The result was very useful for the optimization of construction design and perfection for supporting program.

scholarly journals Research on the Large Deformation Prediction Model and Supporting Measures of Soft Rock Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Junying Rao ◽  
Yonghu Tao ◽  
Peng Xiong ◽  
Chongxin Nie ◽  
Hao Peng ◽  
...  
Keyword(s):  
Large Deformation ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Maximum Displacement ◽  
Deformation Prediction ◽  
Significant Difference ◽  
Rock Tunnel ◽  
Surrounding Rock Deformation ◽  
Bolt Support

The weak surrounding rock has the characteristics of easy softening, poor integrity, low mechanical strength, etc., which makes it easy to induce different degrees of deformation and damage under excavation disturbance and then seriously affects the stability of the tunnel. Carrying out soft rock tunnel deformation prediction research and designing the supporting structure according to the predicted value is of great significance to engineering construction and design. Based on the grey theory, the large deformation of the vault, shoulder, and waist of the soft rock tunnel are predicted, and then the specific bolt support is designed in the maximum predicted value (Smax·R) area. The control effects of different bolts, spacing (d), length (L) on the maximum displacement (Smax·M), and maximum stress (σmax·M) the surrounding rock are analyzed by numerical simulation. Results show that the gray model has high prediction accuracy, the best prediction time is one week, and the maximum error is only 2.99%; with the decrease in d, resin bolt support has a significant supporting effect compared with mortar bolt support, with Smax.M and σmax·M reduced by 64.38% and 10.35%, respectively; as the L of bolt increases, compared with the mortar bolt support, the resin bolt support has a more obvious restraining effect on the surrounding rock deformation, and Smax·M and σmax·M are reduced by 28.20% and 10.00%, respectively; when 4.5 m < L < 6.0 m and 0.6 m < d < 0.7 m, resin bolt support should be adopted; in other ranges, mortar bolt support or resin bolt support has a less significant difference in controlling surrounding rock deformation.

Rheology-Based Stability Analysis of Soft Rock Tunnel in Construction Suspension

2014 ◽  
Vol 934 ◽  
pp. 129-135
Author(s):  
Su Min Zhang ◽  
Yong Quan Zhu
Keyword(s):  
Stability Analysis ◽  
Cross Section ◽  
Back Analysis ◽  
Soft Rock ◽  
Calculation Model ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Rock Tunnel ◽  
Primary Support ◽  
Water Contents

Suspension in tunnel construction usually cause tunnel callapse in weak ground if the suspension time is long. Dongkeling tunnel on Guizhou-Guangxi line being as the engineering background, the indoor rheological experiment and back analysis were performed to obtain the rheological model and parameters of the surrounding rock, and the 3D viscoelasto-plastic calculation model was established to find the evolving rules of deformation at critical locations under two different water contents. It was found that the primary support has little effect on rheology of tunnel work face but on the cross section, and decreasing the water content of the surrounding rock to medium or low saturation level favors the tunnel stabillity greatly for water abundent tunnels.

Application of Long Anchor in Support Optimization of Soft Rock Tunnel

2013 ◽  
Vol 368-370 ◽  
pp. 1614-1624
Author(s):  
Yang Sun ◽  
Jian Ping Chen ◽  
Wei Zheng ◽  
Li Yu
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Parameters Optimization ◽  
In Situ Monitoring ◽  
Rock Deformation ◽  
New Thought ◽  
Supporting Structure ◽  
Rock Tunnel ◽  
Surrounding Rock Deformation

supporting structure parameters optimization is always a research focus in soft rock tunnel. Combined with Youfangping tunnel in Guzhu highway, the scheme of long anchor supporting has been provided. Usually the length of systematic anchor was determined according to experience, it often not reasonable. In order to determine the length of anchor, in-situ wave velocity test and theoretical calculation was used, and with the consideration of safety and economy, the length of anchor was determined as 4.5m finally; At the same time combined with in-situ monitoring measurement, two test sections was selected, and with the comparison of the designed supporting scheme and the original strong supporting scheme, it can be found that: no matter from the sight of surrounding rock deformation, stress applied on surrounding rock or force pattern of supporting structure, the supporting form by lengthening anchor can control surrounding rock deformation more effectively, can improve the bearing capacity of surrounding rock fully and improve the effect of supporting structure. And the supporting scheme of long anchor was more reasonable than the strong supporting scheme. This long anchor supporting scheme can provided new thought to supporting design of soft rock tunnel in Guzhu highway.

scholarly journals Research on Supporting Method for High Stressed Soft Rock Roadway in Gentle Dipping Strata of Red Shale

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 423
Author(s):  
Chunde Ma ◽  
Jiaqing Xu ◽  
Guanshuang Tan ◽  
Weibin Xie ◽  
Zhihai Lv
Keyword(s):  
Failure Process ◽  
High Stress ◽  
Soft Rock ◽  
In Situ Stress ◽  
Mechanical Parameters ◽  
Deformation And Failure ◽  
Deep Mine ◽  
Plastic Energy ◽  
Roadway Stability ◽  
Phosphate Mine

Red shale is widely distributed among the deep mine areas of Kaiyang Phosphate Mine, which is the biggest underground phosphate mine of China. Because of the effect of various factors, such as high stress, ground water and so on, trackless transport roadways in deep mine areas were difficult to effectively support for a long time by using traditional supporting design methods. To deal with this problem, some innovative works were carried out in this paper. First, mineral composition and microstructure, anisotropic, hydraulic mechanical properties and other mechanical parameters of red shale were tested in a laboratory to reveal its deformation and failure characteristics from the aspect of lithology. Then, some numerical simulation about the failure process of the roadways in layered red shale strata was implemented to investigate the change regulation of stress and strain in the surrounding rock, according to the real rock mechanical parameters and in-situ stress data. Therefore, based on the composite failure law and existing support problems of red shale roadways, some effective methods and techniques were adopted, especially a kind of new wave-type bolt that was used to relieve rock expansion and plastic energy to prevent concentration of stress and excess deformation. The field experiment shows the superiorities in new techniques have been verified and successfully applied to safeguard roadway stability.

Prevalence and factors associated with smoking among Tunisian secondary school-adolescents

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Houda Ben Ayed ◽  
Sourour Yaich ◽  
Mariem Ben Hmida ◽  
Maissa Ben Jemaa ◽  
Maroua Trigui ◽  
...  
Keyword(s):  
Associated Factors ◽  
Age Groups ◽  
High Stress ◽  
Smoking Behavior ◽  
Multivariate Logistic Regression Analysis ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Current Smoking ◽  
Part Time ◽  
High Stress Level

AbstractObjectivesThis study aimed to estimate the extent of smoking experience among high and middle school adolescents in Southern Tunisia and to delineate its potential associated factors.MethodsWe conducted a cross-sectional study among middle and high school-adolescents in the governorate of Sfax, South of Tunisia in the 2017–2018 school-years. A questionnaire was anonymously administered to a representative sample of 1,210 school-adolescents randomly drawn.ResultsThe mean age of the school-adolescents was 15.6 ± 4.2 years. The prevalence of lifetime smoking was 16.7% (95% CI=[14.7–18.8%]) (boys 32.6%; girls 5.9%;p<0.001). Among the respondents, 13.9% (95% CI=[11.9–15.8%]) were current smokers. In multivariate logistic regression analysis, independent associated factors of current smoking were male gender (Adjusted (AOR)=10.2; p<0.001), 16–17 and 18–19-year age-groups (AOR=2; p=0.005 and AOR=2.6; p=0.001, respectively), below average academic performance (AOR=5.2; p=0.012), divorced parents (AOR=3.9; p=0.007), family monthly income ≥800 dollars (AOR=2.1; p=0.001), having a part time job (AOR=3.9; p<0.001) and a perceived high stress level (AOR=1.98; p=0.008). Secondhand smoke (AOR=1.8; p=0.011) and concomitant alcohol drink (AOR=14.56; p<0.001) were independent predictors of current smoking, while high education level of the father was independently associated with lower prevalence of current smoking (AOR=0.17; p<0.001).ConclusionThe prevalence of lifetime and current smoking were relatively high in Southern Tunisian middle and high schools. Multilevel influences on youth smoking behavior had been identified, which reflected the need to conceive appropriate school interventions and effective antismoking education program.

scholarly journals Study on the Mechanical Behavior of Double Primary Support of Soft Rock Tunnel under High Ground Stresses and Large Deformation

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhe Liu
Keyword(s):  
Mechanical Behavior ◽  
Large Deformation ◽  
Design Method ◽  
Characteristic Curve ◽  
Soft Rock ◽  
Support Design ◽  
Deformation Amount ◽  
Secondary Lining ◽  
Rock Tunnels ◽  
Primary Support

Double primary support structures could effectively solve the problem of large deformation of surrounding rock for soft rock tunnels. However, the mechanical behavior of this new support structure is still incomplete, and the design method should be revised. Based on the theory of energy conversion, this paper analyzes the support characteristic curve of double primary support and puts forward the dynamic design method of double primary support. Considering that the secondary lining can be set after monitoring the deformation amount and deformation rate of the first primary support, its support parameters can be dynamically adjusted according to the actual situation. By applying the double primary support design method in the Maoxian tunnel of Chenglan Railway, the field monitoring results show that the double primary support has a significant effect on the energy release of surrounding rocks, greatly reducing the load acting on the secondary lining and ensuring the safety and reliability of the tunnel structure.

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