Lan Qiao

Experimental Study on Carbonation and Steel Corrosion of High Volume Fly Ash Concrete

Abstract-The strength, anti-carbonation resistance and steel corrosion resistance properties of high volume fly ash concrete are studied in this paper. The results show that the strength of concrete for 28d is higher than that of normal concrete, as well as the anti-carbonation resistance, when the mixing amount of fly ash is 30% and 40% and the W/B is below 0.4. The anti-carbonation resistance of C50 is the best of all due to its low W/B, there is almost no carbonation when the mixing amount of fly ash is 30% and 40%. The carbonation depth for 56d is still below 10 mm when the mixing amount of fly ash is 60%. For the concrete of C50 with the W/B of 0.32, the steel weight loss ratio is 0.2% when the mixing amount of fly ash is 50%, so it has good steel corrosion resistance properties.

Energy characterization based assessment of pillar recovery

A number of pillars are left developed in some of the Chinese metal mines due to careless mining and lack of proper planning. There are pillars in such mines which do not contribute much in supporting the covered rock mass. Re-exploitation of these standing (non-supporting) pillars can be an efficient method for resource recovery if the remaining pillars ensure the stability of the covered host rock. In this study, a tungsten mine in Jiangxi Province, China, was chosen as a case for studying this pillar recovery scheme. Based on accurate in situ stress measurement data in the original and disturbed host rock, the storage energy in the rock mass could be estimated by numerical simulation methods. After comparing the storage energy to the sum of the fractured energy consumption and friction energy consumption (obtained from lab tests), the recyclable pillars can be identified by a cyclic judgment programming process.

Laboratory Testing on Energy Absorption of High-Damping Rubber in a New Bolt for Preventing Rockburst in Deep Hard Rock Mass

With the increase in mining depth, the deep hard rock mass is under threat of rockburst under high geostress, high temperature, high osmotic pressure, and strong disturbance. To reduce the probability and strength of rockburst, a new energy-absorbing bolt for guaranteeing the stability of deep hard rock mass was developed utilizing the energy absorption characteristic of high-damping rubber. To analyze the practicability and obtain the quantified behaviors of this new energy-absorbing bolt, a series of impact tests on specimens of high-damping rubber, granite, and granite–rubber composite specimens was carried out by a split Hopkinson pressure bar (SHPB) method. Further, considering the different working depths with different rock temperatures, the dynamic energy-absorbing characteristics of high-damping rubber under different temperatures were tested. The testing results show that the new energy-absorbing bolt can consume the storage energy in host rock effectively, and the environmental temperature will produce certain effects on the energy-consuming rate. In addition, the optimal energy-absorbing thickness–diameter ratio of high-damping rubber was confirmed by SHPB tests.

Stability Analysis of Rock Slope Based on Preferred Structural Plane

Aimed at stability of rock slope, the attitude of structural plane is statistically analyzed with a combined method of rose diagram and pole equidensite diagram, and the preferred structural planes which are dominant in stability of slope were further determined by a lot of factors such as the terrain and topographical features of slope, the lithologic characters and the development of structural plane. Besides, the stereographic projection method is applied to qualitative analysis for the stability of rock slope. The results show that preferred structural plane can effectively reveal the nature of rock slope stability and provide a dimensional discriminant approach for stability of rock mass slope.

Effect of Humidity on Delayed Propagation of Indentation Crack under Sustained Electric Field in Ferroelectric Ceramics

The effect of humidity on delayed propagation of indentation crack in lead zirconate titanate ferroelectric ceramics under sustained electric field was investigated. The results indicated that delayed propagation of indentation crack could occur in humid air at 98%RH without electric field but it did not in air at RH uf0a3 30%. The threshold electric field and incubation time for delayed propagation of indentation crack increased but the increment of propagation length decreased with decreasing the humidity. When the electric field is large of 0.14 times of the coercive field, the delayed propagation could also occur in vacuum.

Laboratory Investigation of Energy Propagation and Scattering Characteristics in Cylindrical Rock Specimens

Deep mining involves complex geological environments. Moreover, along with strong disturbance, rockbursts and other severe dynamic hazards can occur frequently. Energy theory is widely regarded as the most appropriate method for understanding the mechanism of deep dynamic problems. When modeling dynamic disasters, energy theory includes the energy storage, energy accumulation, and energy transfer. To study the energy transfer characteristics in rock, a series of split-Hopkinson pressure bar (SHPB) impact tests were conducted with long granite specimens (400u2009mm in length and 50u2009mm in diameter) and modified incidence bars (having the same cross-sectional area but different shapes). The test results indicate that the impact energy decays exponentially with an energy attenuation coefficient of −0.42. For the scattering characteristics of energy in the rock, the scattering distance is found to be approximately three times the specimen diameter, which is very similar to Saint-Venant’s principle in elastic mechanics.

Implementation of the strain hardening model into buffer material in high level waste repository

Engineered Barrier System (EBS) primarily provides a protective cover for the High Level Waste (HLW) canisters. In addition, it functions as an efficient hydraulic and chemical barrier system. For in situ disposal applications, the ideal buffer material is bentonite and it is fabricated into blocks to build EBS. Currently, traditional methods introduce significant errors in constitutive modeling of those modeled blocks. In this paper, the particular failure laws and stress-strain laws of bentonite blocks were furnished from a lot of uniaxial and triaxial tests. Also, it showed that the stress-strain relations given by the traditional constitutive relations did not correspond to the failure forms of bentonite specimens in the experiments. On this basis, the relations between internal friction angle, cohesion and plastic strain were analyzed so that a new strain hardening model was established under the framework of Mohr-Coulomb criterion. In the end, a series of 3D computation of HLW disposal were carried out using the software FLAC3D, where the proposed strain hardening model led to satisfactory prediction of the buffer materials.

Measurement and distribution research of in-situ stresses of Yuyuan area in Shanxi province

Yuyuan area of Linfen city is located in Linfen basin of Shanxi province. It is very complex that the constitutive structures is in the area because of the effect of Lvliangshan swell and Taihangshan swell, etc. Combined research of CSIRO in-situ stress measurement and theory of geomechnics is carried on in this paper. Values and directions of stresses are obtained and the relationships between the in-situ stresses and constitutive structures are analyzed. The results show that the direction of max principal stress is NNW, and the value are all about 14Mpa. It can be concluded that the distribution is mainly effected by Zijinshan Fracture.

Establishment of a cellular automata model for the prediction of landslide based on GIS technique

Currently the geographic information system (GIS) is mainly applied to describe and analyse static information of space, lacking of analysis of space-time and ability of dynamic simulation.. The changes of landslides can be recognized the spatio-temporal process, bringing new challenge and need to GIS analysis of space. Cellular automata Cellular automata (CA), is a “bottom-up” dynamic simulation modeling and simulation frame-work, which is naturalness, rationality and feasibility in simulating the space of complex systems with space-time dynamic evolution. Using loose coupling method to integrate the GIS technology and CA, establish a suitable forecasting model of highway landslide disaster, and forecast the development trend of Da Zha Zi landslide by using CA model.

Integrated Application of Three In Situ Stress Measurement Techniques

The CSIRO overcoring stress relief and hydraulic fracturing methods are the most popular methods used for the measurement of in-situ stress at depth. One major advantage of the CSIRO overcoring stress relief method is that the three dimensional state of stress can be obtained, but the measurement must be done in an excavated tunnel[1]. Hydraulic fracturing method can be carried out on the ground surface, but it assumed that one of the principal stresses direction is vertical[2,3]. In terms of the disadvantages of the two methods, the techniques based on core orientation and acoustic emission behavior of rocks are incorporated in the in-situ stress measurement in order to obtain the in-situ stress conditions at depth in Shuichang Iron Mine. According to the comparison of the measurement data obtained from the acoustic emission test in the laboratory and CSIRO overcoring stress relief measurement in the field, effectiveness of the acoustic emission test is confirmed. In addition, the relationships between in-situ stresses and tectonic settings are analyzed. Finally, the distribution of in-situ stresses in Shuichang Iron Mine is given, which provides a meaningful guideline for the following mining and design.