Abstract:Collapse hazards are frequent in the Sichuan-Tibet Transportation Corridor of Dongcuoqu Basin which is a significant geological risk source for the construction and safe operation of major projects in eastern Tibet. Based on field investigations，the distribution patterns and developmental characteristics of collapse disasters in the study area were summarized， and the formation mechanisms and evolution model of the collapse-debris flow hazard chains were analyzed. The results show that the collapse disasters in the Dongcuoqu Basin has a banding distribution along both sides of the river and faults in space， and concentrately distributed in the lighter and harder strata. The vertical distribution of the collapse is mainly controlled by the convex folded slope morphology and elevation. The development characteristics of collapse are caused by the slope structure， which led to 3 collapse models namely bending-toppling-type， pulling-sliding-type and composite-type. The collapse in the region is featured of high-altitude initiation and remote movement， and the scale of the collapse is significantly influenced by the elevation， height difference and gradient of the collapse source area， while the grain size and movement distance of the deposits are closely related to the lithology. The collapse disasters in the area have a typical chain-type evolution process of collapse-debris flow-river blocking， and the disaster and chain generation process is mainly controlled by factors such as freeze-thaw and topography， among which the giant collapse-debris flow hazard chain is mainly triggered by earthquakes. The research results can provide reference for the prevention and control of landslide disaster risks in human engineering activities in the area.

Abstract:The dip angle in the red bed of eastern Sichuan is generally relatively small， a special form of sliding-buckling deformation appears on the gently inclined and consequent slope. Compared to bedding-sliding， its failure、 stress and deformation are more complicated. In this paper， based on the analysis of the deformation mode of Xinglang slope， the damage process and micromechanical analysis are carried out based on PFC2D software. The results revealed that： due to the topographic features of steep at the top and slow at the bottom which affected by the wide and gentle folding in east Sichuan， the main reason why the sliding-buckling happens is the stress concentration caused by the gentle rock stratum and old landslide accumulation. The deformation damage mode is analyzed into three stages： sliding-bending bulging， strong bending-bulging and sliding-buckling. The displacement of the model damage nephogram shows that the rock body faults and shear characteristics due to stress concentration exist at the location of monitoring point 2 in the middle of the landslide， which is consistent with the actual investigation. The central buckling of the landslide shoed compressive stress concentration before sliding， when the stress concentrated to certern degree， the rock mass sheared along the bedding or the break zone， by which the deformation pattern of sliding-bending-buckling formed. The research has referrencical significance for the stability evaluation of other similar slope.

Abstract:Based on the consideration of crack surge pressure of perilous rock under the blasting load， physical model of crack surge pressure of unstable rock was established. The formation of crack surge pressure is attributed to the initial velocity exerting to crack water by the blasting power. Through theoretical derivation formula of dynamic water impact pressure perpendicular to dominant fissure and increasing amplitude of crack pressure along the fissure direction were determined. Lastly， this paper gave the calculation expression of crack surge pressure under the blasting load. Taking the perilous rock W2-1 in Wangxia for example， action time to crack water was 0.2~0.25s by the blasting power； crack pressure changed nearly 10% by the blasting power which affected the crack surge pressure markedly.

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:Short anti-sliding pile is widely used as the common treatment measures to landslide， however， its bearing mechanism is not clear. In this paper， the software of Fast Lagrangian Analysis of Continua in 3 Dimension （FLAC^3D） is used to build numerical model of anti-sliding piles to reinforce landslides with different length， the characteristics of deformation of the landslide model and the mechanics of the anti-sliding piles are analyzed， and the mechanics to reinforce the landslide is further revealed. The results show that： （1）the stability of the slope can be increased obviously with the reinforcement by short anti-sliding pile with different length； （2） with the increase of the short pile length，the stress of the pile spreads more evenly， and the integrity of the pile and soil is better， the maximum displacement of slope is reducing with lower reduce rate； （3）The slope destroyed cross over the pile when the ratio of the pile’s free section length to the thickness of the landslide is less than 0.6； （4）the ratio of the pile’s free section length to the thickness of the landslide is suggested to be 0.7~0.9.

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 10^th 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:Enyang District in Bazhong City belongs to the typical red layer area in northeast Sichuan. In recent years， shallow surface soil landslides are very easy to be induced by a large number of human engineering activities and heavy rainfall， which pose a threat to people’s lives and properties. In this paper， a typical geological model is established through analyzing the 25 new near-horizontal soil landslides in Enyang District of Bazhong City in the last 3 years（year 2020-2022）. The basic characteristics of such near-horizontal soil landslides are that the dip angle of rock layer and topographic slope are within 10° （mostly 3°~5°）， which are nearly horizontal， the thickness of soil layer of the slide body is thin at the front edge and thick at the back edge， moreover， a high and steep free face at the front edge of the landslide exists and the interface between rock and soil is obvious. The deformation and damage mode of the landslide is qualitatively analyzed as follows： leading edge slip-tensioning， secondary shear sliding， step-by-step traction sliding， and overall sliding deformation. A typical near-horizontal soil landslide in the area was selected as the study object， and the leading edge and middle-rear surface displacements of the landslide were taking as the main monitoring objects. The rainfall intensity was monitored， and the landslide was professionally monitored by GNSS surface displacement monitoring station， fractometer displacement meter， rainfall meter and other monitoring equipment. The results show that the actual deformation and damage patterns of near-horizontal landslides are basically consistent with the theoretical analysis. The findings of this paper can provide some theoretical support for the same type of landslides in the region when designing professional monitoring programs and formulating precise disaster prevention and avoidance measures.

Abstract:Geological disasters are development in the FAST （Five-hundred-meter Aperture Spherical radio Telescope） protected area which is geological disasters prone area where 132 registered geological disasters exist. Hidden hazards of geological disasters in this area have posed threats to the safe operation of the FAST project. In this paper， the existing geological disasters in the FAST protected area are taken as the research objects， methods of field investigation， data collection and mathematical statistics are adopted to analyze the development characteristics of geological disasters in the protected area. The correlation model of geological disasters is established to study the coupling relationship between the disaster-breeding conditions and influencing factors of geological disasters， the formation mechanism is analyzed and studied，and the prevention and control measures and monitoring suggestions are also put forward. As a result， the landslide in FAST protected area are mainly divided into two mechanical failure modes， namely， “traction type” and “push type”. Small landslides are mostly “traction type”， and medium and large landslides are mostly “push type”. The main failure modes of dangerous rock mass in the area are “toppling”， “falling” and “sliding”. Heavy rainfall and human engineering activities are the main inducing factors of geological disasters in the area. therefore， geological disaster inspection and prevention should be carried out before and after heavy rainfall. Scientific assessment and planning should be made before carrying out geotechnical engineering activities to avoid man-made geological disasters.

Abstract:At present， land subsidence is a geological disaster with significant harm， which seriously affects the coordinated development of regional construction planning， economy， environment， and society， and poses a significant threat to urban development and human life and property safety. Xian County is located in the western part of Cangzhou City， Hebei Province， and is an area with severe land subsidence， which is one of the key flood storage and detention areas in China. Therefore， it is of great significance to classify the prone areas of land subsidence in Xian County and adopt precise prevention and control measures. In this paper， six impact factors namely deep groundwater level， shallow groundwater level， Quaternary thickness， cumulative settlement， settlement rate， and road network density are selected， and each township in the evaluation area is taken as the evaluation unit， the weight of land subsidence influencing factors is determined by the gray correlation method， and the superposition analysis is carried out by the spatial analysis function of ArcGIS to partition the land subsidence susceptibility in Xian County in order to provide suggestions and basis for the scientific prevention and control of land subsidence.

Abstract:Yongxin County is located in the high geological disaster prone area in Jiangxi Province. The type of geological disasters are mainly classified into landslide， collapse， debris flow， ground collapse and so on. Based on the geological environment conditions in the area， through the comprehensive study of 370 geological disasters which occurred over the years， the development law of geological disasters in Yongxin County is summarized. The various geological disaster-breeding environment was analyzed， and the disaster-breeding factors such as topography and engineering geological rock groups related to the development of geological disasters and their effects were studied. The results show that the disaster-breeding environment is controlled and influenced by the topography， engineering geological rock group， slope structure， geological structure， rainfall and human engineering activities. Taking full account of the disaster-breeding environment in the area， with the engineering geological rock group and topography as the main control factors， the disaster-breeding environment of Yongxin County is divided into 3 large areas and 19 sub-areas， which provides technical support for the risk assessment of fine geological disaster investigation and scientific basis for the precise prevention and control of geological disasters.

Abstract:PDC bits are widely used in oil and gas drilling， and geological exploration drilling. However， vibrations and abnormal wear of the bits resulting from them compromise the technical and economic effectiveness of the advanced drilling method. The wedge and conic form PDC cutters proposed by both Chinese and foreign specialists have been somehow effective in preventing the vibrations and abnormal wear of drill bits， and increasing the technical and economic indexes； but they can not eliminate the problem completely. Russian scientists have proposed a new type concave PDC cutter， performed computer simulation， and presented related parameters （concave cone angle and rake angle） through theoretical calculation and analytical comparison. The concave PDC cutter can provide some reference for solving the vibrations of PDC bits； thus， it is noteworthy for us to pay attention to.

Abstract:The geological conditions of Hole 23-2， detailed investigation of coal resources in Tuhongwan-Lijiagou， Baiyin City， Gansu Province are extremely complex， including mudstone with strong water sensitivity， loose and broken coal seam， etc.， and salt paste in between， the hole is prone to collapse， clumping and other problems， and the drilling fluid is easy to be polluted， which puts forward higher requirements for drilling fluid properties. In the past drilling construction of this mining area， problems such as hole wall collapse and significant reduction of drilling fluids viscosity often occurred， which in serious case led to buried drill， solids setting stuck and other drilling accidents， and thereby affecting the efficiency of hole-forming and construction efficiency. In view of the above problems， the causes of borehole wall instability when drilling are analyzed， the effects of salt-paste penetration on the properties of the drilling fluids are evaluated， the adaptability of the system is studied in a targeted way and the film-forming anti-collapse drilling fluids and salt-paste encroachment film-forming environment friendly drilling fluids are selected. During the driiling process， aiming at the water sensitive and spalling and loose strata， the film-forming anti-collapse solid free dilling fluid was selected， and transferred to salt-paste encroachment film-forming environment friendly drilling fluid when encountered salt encroachment. Moreover， technology such as reasonable adjustment and maintenance of drilling fluid formula and performance parameters， wire-line core drilling are adopted to solve the above problem.

Abstract:Well JG-2 is located in Fengshan Town， Jinggu Dai and Yi Autonomous County， Pu’er City， Yunnan Province. The structural location belongs to Jinggu Sag of Simao Basin， and the completion depth is 1829.44m. The lithology of drilling strata are mainly mudstone， sandstone， mud conglomerate， halilith， sylvinite and so on. The mudstone is prone to hydration expansion and spalling， resulting in wellbore collapse hazards. Local loose sandstone is prone to collapse， while halilith and sylvinite are easy to dissolve to form hole enlargement and low salt core recovery rate. In view of the above construction problems， saturated magnesium chloride brine drilling fluid was used when entering the gypsum vein salt formation to successfully complete the engineering drilling and coring tasks. The technical problems such as the dissolution of salt cores such as sylvinite， difficulty to carry coarse particles of salt， bit balling and collapse of loose sandstone were solved. Full salt cores containing the roof and floor part were successfully taken， and high-quality salt cores such as halilith and sylvinite were obtained. The average core recovery rate of the whole well was 97.5% without dissolution. The successful experience of this paper can provide reference for similar potassium salt drilling projects.

Abstract:In Qinghai， Xinjiang and other arid areas of China， some mining site water is brine with high salt content. For convenience， salt water is used to prepare cement plugging slurry. A set of salt-water cement plugging slurry system for geological drilling is developed through the selection of various cement admixtures， and the conventional and plugging properties have been comprehensively evaluated. The results showed good fluidity， filtration reducing property and sedimentary stability， the early compressive and flexural strength of the system is greater， and the final coagulation time is shorter. 5% sodium chloride shows obvious early strength and promoting coagulation for cement slurry. The thickening time of the system at 30MPa and 45~75℃ is 110~170min， the slurry is stable， and the thickening characteristics are good， which can effectively plug up the orifice and seam plate. The saltwater cement slurry system has a good application prospect in the plugging operation of fractured formation in similar areas.

Abstract:The gas hydrate reserve is abundant in the Shenhu Sea area， which provides a large amount of energy reserve for our country， and the problem of the shortage of energy can be solved effectively by means of efficient exploitation. Inhibitor injection method is one of the main methods to extract gas hydrate. Methanol is an excellent inhibitor with good inhibition and low viscosity. In this paper， a three-dimension， three-phase and four-component numerical model for gas hydrate exploitation in the sea area was established according to the actual geological parameters. The dynamic characteristics of hydrate exploitation in hydrothermal methanol solution were studied by means of numerical simulation using the horizontal well layout method with production wells on both sides and the injection well in the middle. The extraction effects of single depressurization method and hot water injection method were compared with that of the methanol inhibitor injection and the results show that the later can increase the reservoir temperature and promote the decomposition of hydrate， which improves the shortcomings of the former two methods. It has higher initial gas production rate， higher initial gas-water ratio and higher hydrate decomposition effect， which is a competitive exploitation method.

Abstract:During the second gas hydrate trial production test， the deep-sea wellhead suction anchor technology was firstly applied in the Shenhu sea area， which provids stable wellhead support for horizontal gas hydrate production wells in shallow soft formations. Through the theoretical calculation and finite element analysis， the self-weight penetration depth and negative pressure demand in the process of suction anchor penetration are studied. At the same time， the construction technology of “step-by-step intermittent self-weight penetration， dragging and continuous negative pressure sinking” was adopted in site， which ensured the successful installation of the first domestically produced deep-sea wellhead suction anchor. The field practice results show that the theoretical calculation results are close to the actual construction situation， and the theoretical analysis can guide the installation of suction anchors at the wellhead. In addition， the penetration construction technology is featured of fast， efficient and safe. The indicators of the wellhead suction anchor installation reached the usage demand. It has referential value for the application of suction anchor technology in the fields of deep-sea oil and gas.

Abstract:With the advancement of engineering construction such as urban subway tunnels and railway tunnels， the horizontal directional geological exploration method has become a new exploration method. Compared to traditional vertical hole construction， it can avoid complex construction environments， save a lot of drilling workload， and have obvious technical and economic advantages. The tunnel directional drilling system has traditional advantages for surface or tunnel exploration， but the horizontal exploration mainly based on coring has higher requirements. The tunnel directional drilling technology needs targeted improvement and upgrading in aspects such as coring process adaptability and drill function module. Focusing on the technical characteristics of horizontal directional exploration， this paper compares and analyzes the adaptability of typical tunnel directional drilling systems in aspects of drill pipe system， horizontal exploration rig， drill assembly and coring tool， directional drilling instrument and drilling informatization， and summarizes the technical integration that must be relied on to build the tunnel horizontal exploration engineering technical system. In response to the requirements for efficient coring operations and variable track drilling operations， the direction for the transformation of the horizontal exploration drilling rig’s high torque and strong feeding capacity， multi process adaptability， efficient drilling capacity， efficient tripping capacity， coring capacity， and power head structure has been clarified. Analyzed the shortcomings and limitations of using rope core drilling tools in directional holes with frequent trajectory changes， and explored the types of information parameters and transmission paths in the process of drilling informatization.

Abstract:Directional drilling technology has the advantages of strong crossing ability and controllable trajectory. In areas where traditional exploration is difficult to implement， directional drilling can leave the hole at a long distance to avoid ground obstacles and conduct exploration in the predetermined area. A certain urban tunnel is undergoing directional drilling in a densely built area. It is selected to leave the hole at a suitable distance at a suitable site， and drilling is carried out along the 1m below the tunnel floor through trajectory adjustment. At the same time， two branch holes are implemented in the upper part of the main hole. The core extraction process is used to perform interval core extraction for all sections， and geophysical tests such as micro motion spectral ratio method and borehole acoustic resistivity are completed. The maximum burial depth of the main hole is 69m， the footage is 650.75m， and the maximum deviation of the trajectory is 0.81m. The successful implementation of the project has proven that the combination of directional drilling technology and geophysical testing technology can make up for the shortcomings of traditional exploration methods， better expose the geological conditions of tunnel surrounding rocks， and provide an effective means for complex urban tunnel exploration. At the same time， it is recommended to develop clear and feasible technical principles and norms to promote the application of directional drilling technology in the field of exploration.

Abstract:Grouting sealing technology in multi-branch horizontal wells has been widely used in the water hazard control of mining wells. However， the quantitative characterization method for diffusion range of grouting in the deep formation is lack of research， therefore references for space and buried depth of multi-branch horizontal wells are inadequate. Aiming at seepage grouting technology for multi-branch horizontal wells and considering the anisotropic permeability， two phase flow of cement grouting and porous water， a numerical diffusion model for seepage grouting and a theoretical model for simplified diffusion radius are built in this paper， and the numerical simulations on the seepage grouting are conducted combining with actual engineering cases. The results show that the seepage diffusion area in anisotropic formations tends to be ellipse. The major axis of ellipse is along the bedding plane which has a larger permeability， while the minor axis is perpendicular to the bedding plane. These researches provide some references for the design of space and buried depth of multi-branch horizontal wells and key parameters optimization for seepage grouting.

Abstract:The technology of drilling with casing is widely used in the field of oil and gas drilling as the feature of hole wall protection， sticking and leakage prevention， and efficiency enhancement of casing operation. However because of the complex condition of formations in coal mines and the limitations of underground space and existing drilling equipment， this technology is not applicated on large-scale to solve the prolem in coal mine i.e. casing operation difficulty， low operating efficiency and so on. Focusing on these problems，taking the Zhaogu Second Mine as an example，based on the analysis of the reason for casing difficulties in complex broken strata， this paper proposed the technology of drilling with casing driven at the bottom borehole，developed the bottom transmitting torque mechanism and made industrial tests in Zhaogu Second Mine. The results showed that the problem of casing non-rotation， no slag discharge and being stuck under conventional casing process were solved by this technology， moreover， the problem of low casing efficiency and easy to form waste boreholes were also solved. This technology has greater advantages in the application of drilling across complex broken strata.

Abstract:In view of the problem of low mechanical drilling speed in the hard rock such as granite and gneiss in the geothermal drilling at present， a mechanical rotary-percussive screw drilling tool is introduced and tested in granite formation of JHR-1 well and gneiss formation of HG-1 well. Compared with the ordinary screw drilling tool， the mechanical drilling speed of the rotary-percussive screw drilling tool increases respectively by 10%， 8.4% and 7.6% in ?215.9 mm well section of JHR-1， ?215.9 mm and ?311.2mm well section of HG-1， and no other side effects exist during the drilling process. The test proves that the mechanical drilling speed can be effectively improved by the use of rotary-percussive screw drilling tool， which provides a foundation for the application and popularization of the rotary-percussive screw drilling tool in the drilling of hard rock such as granite and gneiss.

Abstract:The technical casing depth of shale gas wells in Southern Sichuan Block is 2600~2900 m. Through the previous 11 times of technical casing cementing construction， it is found that the main problems of technical casing cementing in this block are the development of multiple gas layers with active shallow gas， and the Maokou Formation is easy to leak. In the process of cementing， the contradiction between pressure stabilization and anti-leakage is prominent. This paper systematically analyzes the main problems encountered in the process of technical casing cementing of shale gas in Southern Sichuan Block. Through the research on the pressure bearing capacity after plugging in easy-to-leak formations and the design of cement slurry， slurry column structure， displacement， and the auxiliary technology for pressure stabilization， a set of process technology suitable for the cementing of shale gas technical casing cementing in Southern Sichuan Block is formed， and the effect of field application is remarkable.