Abstract:The stability of the slope of an open-pit mine is mainly affected by geological structures such as faults and joint of rock mass. In order to identify the distribution characteristics of the rock mass structural， the Reflex ACT Ⅲ tools were used to unify thecore orientation of 4 geotechnical survey holes. However， the proportion of highly reliable core orientation data for each borehole only 8.05%~34.29%， due to therock mass fragmentation and joint development near the contact zone between granite intrusions and sedimentary rocks， which affects the accuracy of core orientation. Therefore， this article took OTV/ATV survey to obtain lithology and structural characteristics， relationships and direction data effectively and improve the accuracy of geological structure information data of core orientation， through high-resolution， continuous and oriented 360° borehole wall images. Based on this， failure mode of the open pit mine was studied by equatorial polar projection theory and dynamic analysis. According to the result， the main failure mode is wedge sliding failure， with a probability of 12.66%~34.99%， followed by plane sliding， with a probability of 3.40%~20.36%， which provides the foundation for open-pit mining slope control.

Abstract:With the technological development of multi-branch horizontal wells and complex structural wells， hole cleaning technology is facing new difficulties and challenges. The problems urgent to be resolved are how to solve the problem of cuttings-bed under complex geological conditions and complex well type conditions， to help judge and solve the complex situation downhole. The cuttings transport model is adopted based on the mechanism of cuttings transport. The indoor visualization of cuttings transport experiments was conducted to analyzed the cuttings transport patterns. The results show that the critical velocity of drill cutting is the highest at the well slope angle of 36°， and the drill cutting is most difficult to be carried. The trend of model predicted was validated by comparison with experimental results， and a good accordance was obtained. Its field application also indicates a good agreement between prediction and actual situations， which validated the reliability of this model. The model and experiments are of reference significance for borehole cleaning of large displacement horizontal wells.

Abstract:In this paper， taking the rock slope of an open-pit mine in Xizang as an example， based on the site investigation and engineering geological characteristics of mine slope， the engineering geological zoning of mine slope is studied， and the slope stability is qualitatively analyzed and quantitatively calculated by combining the stereographic projection method and Sarma method. The research results show that the slope stability evaluation results were consistent with the current slope status. The slope stability of mining area was not good in general， and the slope in local area has poor stability. Both qualitative and quantitative stability evaluation methods confirm each other， which provides an important basis for slope disaster control design and construction in the next stage， and this has a good reference for similar slope projects.

Abstract:Red beds are typically considered as “prone-to-slide strata”， and shallow soil landslides can easily occur under rainy conditions. Therefore， it is of great importance to study the stability of shallow soil slopes in red bed areas under rainfall conditions. In this research，the shallow soil slopes in the red bed areas of Hunan Province is taken as an example， the stability of shallow soil slopes in red bed areas under different slope gradients， rainfall intensities， saturated hydraulic conductivities， and initial water contents is investigated by employing the modified Green-Ampt infiltration model， the specific impact patterns of these factors on slope stability is also analyzed. When the slope gradient is less than 45°， the safety factor decreases as the slope increases； when the slope gradient is greater than 60°， the safety factor increases with the slope. The wetting front depth changes insignificantly with the rainfall intensity， and the safety factor changes insignificantly with the rainfall intensity； the depth of the wetting front increases and the safety factor of the slope decreases as the saturated hydraulic conductivity increases； the safety factor decreases as the initial water content increase. The results can provide a theoretical basis and practical guidance for slope protection engineering in red bed areas.

Abstract:In order to manage a landslide， a numerical analysis model of the slope was constructed based on the on-site investigation data， taking the inflection point of the displacement of the characteristic point of the slope as the criterion， and adopting the strength discount method to determine the stability coefficient of the natural working condition of the slope to be 1.05， it was determined that the stability level of the slope did not meet the requirements of the engineering specification， and it was in the state of understability. Combined with the numerical analysis results， experts’ on-site analysis opinions and the mechanism of slope reinforcement measures， three kinds of reinforcement and management programs are determined， Program 1 is “Circular anti-slip piles + anchors + intercepting and draining”， Program 2 is “Square anti-slip piles + Circular anti-slip piles + Anchors + intercepting and draining”， and Program 3 is “Square anti-slip piles + Circular anti-slip piles + Intercepting and draining”. Based on the finite element numerical model to analyze the stress field， displacement field and slope stability coefficient changes of the rock and soil body， anti-slip piles and anchors， the stability coefficients of natural working conditions of the slope corresponding to the three reinforcement schemes were calculated to be 1.39， 1.28， and 1.18， which were 32.4% higher than those before reinforcement， and the stability coefficients of the natural working conditions were calculated to be 1.39， 1.28， and 1.18， which were 32.4% higher than those before reinforcement. Before the reinforcement， the stability coefficients of the natural working condition of the slope were 1.39， 1.28 and 1.18， respectively， which were 32.4%， 21.9% and 12.4% higher than those before the reinforcement； after comprehensively comparing the reinforcement measures of the three kinds of reinforcement schemes and the changes in the stress and displacement of the slope， as well as their reinforcement effects and economic levels， Scheme 1 was comprehensively determined as the final reinforcement scheme.

Abstract:In order to accurately evaluate the threat to buildings and people’s lives and properties in the run-out path after slope failure， this paper takes a landslide in Chenzhou as an example， simulates the failure mechanism of large deformation under natural and rainstorm conditions after excavation of this slope based on the material point method， calculates the run-out distance， and compares the results with the finite element method. The results show that： （1） Before excavation， the slope is basically stable under natural condition and unstable under rainstorm condition， while after excavation， the slope is unstable under both conditions； （2） The sliding distance of the landslide increases significantly after excavation， and the sliding distance under natural conditions and rainstorm conditions is 20.11 and 24.12m respectively； （3） By comparing the results of stability and large deformation analysis， it can be seen that excavation and rainfall are the two main factors causing slope instability. Calculating the sliding distance after slope instability can provide theoretical reference for evaluating the threat to buildings on the sliding path， and is of great significance for improving slope safety protection.

Abstract:Refined study of the influence of the water level flucration on bank slope stability is of great significance. Taking the Shigenao Landslide in Baihetan Hyreopower Reservoir as an example in the paper， based on geological conditions， combined the monitoring data of universal geo-hazrad monitoring instrument， rainfall data from the meteorological station and reservoir water level fluctuation data， the stability of the slope in different water levers and water lever dropped over 20d in differente speeds was simulated by the finite element method. The results show that the safety factor increases about 17.6% in the stable seepage flow compared with the condition of transient seepage， the stability increased as the reservoir water level rises， otherwise the stability decreases. The greater the drop rate of reservoir water level， the worse the stability， and the stability decreases by about 3.2% when the develeration rate increases by 0.5m/d. The factors of stability decreases significantly in the early stage， and reached to the lowest in the 10th day，which is highly coincide with the GNSS monitoring data. The monitoring data predicted the occurrence of the landslide in advance which shows the monitoring effect and forewarning funtion of the universal monitoring instrument.

Abstract:This paper takes a deep fill slop in Xianning Hubei as the construction background. The numerical simulation software—Geo-studio was adopted to analyze the influence of rainfall-surcharge coupling effect on the stability of deep fill slope， the pore water pressure distribution inside the slope and the influence of constant rainfall and surcharge at the top of slope on the stability coefficient were also analyzed. The results showed that the original slope was in metastable state under the condition of rainfall and surcharge at the top of slope， the stability coefficient decreased with the rainfalls time， compared with the constant rainfall， the surcharge load had a greater impact on the stability of fill slope. To the end， a reinforcement scheme of a slope scouring and load reduction and waterproof surface was proposed. The numerical simulation results confirmed the feasibility of the scheme， which meet the requirement of the construction， meanwihile， the rationality and validity of the simulation results were verified.

Abstract:There are a large number of glacier relics in Southeastern Tibet， forming a large number of loose accumulations， which are prone to disasters. There are many voids in the moraines， and the structures are unstable. The technology of grouting reinforcement by steel screen pipe for moraines was studied with discussion of the construction technologies， the reinforcement mechanism， as well as the design method. The numerical simulation was also implemented. The field tests were performed， and the results showed that the effective reinforcement radius of shallow surface grouting of moraine is 20~55cm； the soil cohesion， internal friction angle and compression modulus improved after grouting reinforcement； the vertical permeability coefficient of the soil becomes smaller； the preferred grouting pressure is 0.5 to1.0MPa， the water/cement ratio 2、1， the ratio of the grouting hole spacing to the effective reinforcement radius not greater than 8. Through field tests， a screen pipe grouting process has been formed on the basis of the 3.5 cubic air compressor， YT28 rock drill， hollow self-drilling bolt and pneumatic grouting machine， which is suitable for inconvenient traffic and poor construction conditions.

Abstract:The Kriging method， which is an efficient and accurate metamodel， is widely used in slope reliability analysis. However， traditional methods couple the Kriging model directly with the Monte Carlo simulation method for reliability analysis， which leads to excessive memory usage or even overflow in high-dimensional slope reliability calculation with small failure probability， hence failure to find the solution. To this end， this paper proposes a Subset simulation method based on the Kriging metamodel to efficiently solve the problem of small probability slope reliability analysis. A single-layer cohesive soil slope and a practical soil slope are used to verify the effectiveness of the proposed method， and different regression models and related function models as well as the number of training samples are explored for the accuracy of the method. The results show that： （1）The proposed Subset simulation method based on the Kriging metamodel can effectively calculate the failure probability of slopes， and is more efficient than the traditional method； （2）During the construction of the Kriging model， the calculation accuracy of the model can be achieved when the number of training samples reaches10 times that of random variables. In addition， the number of additional training samples has little effect on the calculation results.