When the stress in geotechnical material is close to strength limit state, it is sensitive to external disturbed loads; it is called disturbance effects. The excavation depth of tunnels and mining depth of the ore are buried below 500 m. Although the mining depth of some coal mines is only 250 to 400 m, the surrounding rocks around the roadways are weak; thus they are vulnerable to weathering and hydrolysis. Similarly, in railroad, traffic, water conservancy, we also encounter soft rock. These soft rock caverns or chambers produce greater deformation, and in particular, when affected by the disturbance, may even cause major security incidents. These problems have become major difficulties in mining activities.
Stress state in surrounding rock of roadways is within strength limit neighborhood; creep of surrounding rock is the main deformation, which can be caused by random disturbance loads ( mining, excavating and blasting ). Surrounding rock of tunnels, roadways, chambers and caverns in deep mining or soft rock will produce large creep deformation when the stress in the rock is close to its ultimate strength. Most of the creep deformation is caused by disturbance loads. Previous studies on creep include uniaxial compression, uniaxial tension, triaxial compression, weak plane shear and relaxation. Most of the theoretical research focused on element combinations, empirical, endochronic model, and they were conducted under the condition of static load. So far, however, little empirical research has been done to investigate rock respose to disturbance. Hence, the testing system can simulate on the creep properties of rock materials and provide theoretical evidences for analysis of rock stability under disturbance loadings in geotechnical engineering.
The book contains the main ideas of the design and manufacturing of a new creep testing system that is set up at Shandong University of Technology and Science (SUTS) and China University of Mining and Technology (Beijing). This testing system includes a creep testing machine, triaxial pressure box, system of disturbance loading and measurement. The testing machine is capable of performing creep tests under blasting disturbance and gravity impacting, and can evaluate the disturbance effects of the rock creep. Finally, in order to verify the performance of the equipment, a series of creep tests were performed on rock specimens and the axial and lateral deformations were measured using dial gauges and strain gages.

Part One Testing System Design

1 Introduction 3

      References 6

2 Development of Testing System of Disturbance Effects to Rock Rheology 9

      2.1 Objectives and Requirements of the Testing System 9

      2.2 Structure Design of the Testing System 10

      2.2.1 Overall Structure of the Testing System 10

      2.2.2 Design Parameters 11

      2.2.3 Technical Requirements 11

      2.2.4 Scheme Design for Axial Gravity Force-Amplification 12

      2.2.5 Design and Manufacture of the Test System 18

      2.3 Structural Design of Triaxial Cell 31

      2.3.1 Basic Requirements of Triaxial Cell and Stress-Strain Measure me ent System 31

      2.3.2 Overall Design of Triaxial Cell and Stress-Strain Test System 31

      2.4 Design Lectotype of Disturbance Loading and Measurement System 31

      2.4.1 Disturbance Loading Mode 31

      2.4.2 Design of Disturbance Load Measurement 32

      2.4.3 Design for Axial Force Measurement 36

      2.5 Summary 37

      References 37

3 Rigidity and Measurement Accuracy of the Test System 39

      3.1 Conditions and Method of Rock Specimen Non-Rupture 39

      3.2 Analysis of Test System Stiffness. 42

      3.2.1 Definition and Calculation Formula of General Stiffness ·42

      3.2.2 Calculation of Test System Stiffness· 43

      3.2.3 Calculation of Rock Specimen Stiffness 45

      3.2.4 Analysis of Rock Specimen Rupture 45

      3.2.5 Measures to Prevent Rock Specimen Rupture 46

      3.3 Analysis of Test System Accuracy 47

      3.3.1 Concept of Measurement Accuracy and Precision of Testing Study 47

      3.3.2 Analysis of Test System Accuracy 47

      3.4 Summary 50

      References 51

Part Two Testing System Verification

4 Creep Compression Test 55

      4.1 Uniaxial Compression Creep Test 57

      4.1.1 Testing Procedures and Setup 58

      4.1.2 Creep Deformation 63

      4.2 Triaxial Compression Test 71

      4.2.1 Test Setup and Procedures 71

      4.2.2 Rock Creep Test Under Constant Confining Pressure 72

      4.2.3 Creep Testing Under Variable Confining Pressure 73

      4.3 Summary 78

      References 79

5 Rock Creep Under Disturbance 81

      5.1 Gravity Impacting Disturbance Test 82

      5.1.1 Modes of Disturbances Loading 82

      5.1.2 Creep Load 82

      5.1.3 Disturbance Load 84

      5.1.4 TestResults and Analysis 85

      5.2 Blasting Disturbance Tests 88

      5.3 Summary 91

      References 93

Index 95

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