Abstract: Based on the mesoscopic damage theory and the finite element method, a numerical code RFPA was applied to investigate the rock fragmentation by three TBM cutters loaded one after another in different time interval. The whole process of crack initiation and propagation was successfully simulated by the cutters loaded with different step intervals. The time interval of the disc cutters has significant influence on the fracture patterns and the rock breaking efficiency. The simulated results show that there are three types of breakage mode of the rock subjected to compression by the cutters.
Abstract: Based on in-situ observational data, we analyzed energy features of strong ground motion induced by short delay blasting in unsaturated loess field through three aspects of time history, frequency spectrum and attenuation. For time histories, the data show exploding ground motion has two essential characteristics, i.e. larger peak ground acceleration (PGA) and shorter duration. Analysis results reveal the effective duration (ground acceleration exceeding a certain magnitude) is the pivotal factor influencing design effects of the blasting. The spectral response, meanwhile, attenuates with the increase of observational distances (apart from the centre of exploding field), especially for those higher frequency components. Values of H/V figured relative features of horizontal component to vertical one of frequency spectrum of exploding ground vibration become greater while distances widen. As exploding energy accumulated, moreover, lower frequency energy distinctly increases and the feature of frequency spectrum of the strong shock gradually approaches an actual seismic oscillation.
Abstract: Matric suction plays a significant role in the unsaturated slope stability and receives a rising interest in how matric suction affects the unsaturated slope stability. According to the shear strength theories and soil-water characteristic curve of unsaturated soils，matric suction parameters were proposed to study the influences of matric suction on unsaturated slope stability by applying in strain-softening constitutive model and using catastrophe theory as a tool. The results show that the unsaturated slope safety factor depends on the stiffness ratio，the softening coefficient，the suction sensitive factor and the relative displacement ratio. However，when the system reaches the limit equilibrium circumstance，the fundamental factors particularly affecting the unsaturated slope stability are the stiffness ratio of two media and the softening coefficient of the sliding surface，and the further trend between matrix suction and unsaturated slope stability is the same as the changes of the suction impact factor.
Abstract: This study has been carried out to determine how the fines content affects the post liquefaction strength and deformation characteristics of sand. With the GDS dynamic triaxial system, a series of monotonic undrained compression tests of the sand after liquefaction with variation in fines content from 0 to 40% were conducted, and effects of fines content on the post liquefaction strength and deformation characteristics of sand were analyzed. Results show that with the addition of fines up to a fines content of 30%, the stress-strain curve moves downward and axial strain at low intensive stage is increased, beyond this critical value of fines content the trend is reversed. However, shear strength of post-liquefied sand first decreases with increasing fines content, and beyond the critical value of fines content it increases with increasing fines content at the strength recovery stage when are subjected to monotonic loading. At the same time, the strength recovery rate decreases firstly and then increases with the increasing fines content.
Abstract: The estimation of country rock stability in underground engineering is the important basis for carrying out engineering design and formulating corresponding engineering measures. The interval form of quality standard, the value of resolution coefficient ρ and the weight of correlation degree are seldom takend consideration by the traditional gray correlation analysis model, an improved gray correlation analysis model is used to analyze the five indices of influencing the country rock stability: rock quality designation RQD, moisture compressive strength Rw, integrity coefficient Kv, structure surface strength coefficient Kf, groundwater seepage measurement W/L. The results show that the improved correlation analysis model is superior in its objectivity and applicability as well as certain practical value in evaluating country rock stability or other evaluation problems.
Abstract: Shale characteristic is very important in the exploitation. Using NMR determine the pore distribution of shale, it is found that the pore radii of shale samples is mainly between 3-10nm, which is in accordance with the results of mercury injection. NMR is also applied in the determination of movable fluid of shale, gas saturation of the measured 14 samples is mainly between 12% and 28.1%, no relationship is found between gas saturation and porosity or permeability.
Abstract: Based on the Bai Jiabao landslide model test, the landslide’s similar materials are studied.According to the similar criterion theory , the methods of uniform design and orthogonal design are used to determine the ratio of materials. The results is showed that the similar materials of the heavy grain of sand, the heavy crystalline powder, the river sand, the flour, silty sand have the similar physical properties with the Bai Jiabao Landslide and that they are used as materials to simulate the landslide in the model test are suitable.
Abstract: Vacuum-surcharge combined preloading method have been become the most commonly used method on the dredger fill and saturated soft clay soil consolidation beside the coast. The long time of consolidation is one of this method’s most characteristics, as we always think that 3 months is the academic time. In fact, we always can’t accomplish the consolidation of saturated soft clay soil by using vacuum-surcharge combined preloading method in 3 months because of the complex nature of the soil horizon and the effects of the construction technology. The main mission of the article is to supply a substantial time and a reliable basis that are needed by the vacuum-surcharge combined preloading method and the construction period. The main data sources are come from the ground treatment project of a cogeneration power plant in Zhuhai Guangzhou. We adopt the exponential curve fitting method and the method of Asaoka to count the degree of consolidation of the saturated soft clay soil.
Abstract: Non-coaxiality has been recognized as an important feature of grain materials in geotechnical engineering. Without considering the non-coaxiality in structure design will lead to an unsafe result. Studies on the non-coaxial soil behaviour have been carried out both using numerical simulation and experimental testing by several researchers. To discuss the non-coaxiality of sand, it is essential to carry out tests under various stress paths. HCA is a valuable device to investigate the soil behaviour under various stress paths. In this paper, a review of the experimental work on non-coaxial soil behaviour especially using HCA is presented to help the understanding of both non-coaxiality and the use of HCA.