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2005, 24 (21): -0 doi:
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RESEARCH AND NEW PROGRESS IN GROUND ANCHORAGE

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2005, 24 (21): -3803 doi:
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[PDF 341 KB] (2020)

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The ground anchorage technology has been widely used in slopes，foundation pits，mines，tunnels，underground caverns，dams，resistance to overturning and floatations，etc. in China with remarkable success. It is expounded more comprehensively that major achievements and the latest progresses in ground anchorage from the application field and scale，standardized construction，reinforcing mechanical effect，load transfer mechanism as well as load-dispersed anchors (cables)，repeated grouting technique，hollow-grouted anchor and underreamed anchor，soil nail and composite soil nail，drilling machines and monitor techniques，etc. in China. Meanwhile，some opinions are proposed on several key problems，concerning the development of ground anchorage in China，such as the design，type and adaptability，corrosion and protection，long-term working behavior and safety evaluation，as well as the research direction，etc. of the ground anchors.

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APPLICATION OF STRENGTH REDUCTION FEM TO YUANJIANG—MOHEI EXPRESSWAY CUT SLOPE STABILITY ANALYSIS

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2005, 24 (21): -3812 doi:
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The Yuanjiang—Mohei expressway deep cut rock slope stability analysis is carried out by strength reduction finite element method. The shear strength reduction FEM is adopted to analyse the interaction between the soil and stabilizing structural of frame beam with prestressed anchor rope. The frame beams are simulated by beam No.3 element in ANSYS software；and the prestressed anchor ropes are simulated by anchor-hold force. The construction processes are simulated by element“kill and alive”technique of ANSYS. With the shear strength reduction，the rock slope nonlinear FEM model reaches instability，and the numerical non-convergence occurs simultaneously. The safety factor is then obtained by shear strength reduction algorithm. At the same time the critical failure surface and the frame beam pressure distribution and internal forces (bending moments and shear force distribution) of stabilizing structure are obtained automatically. For this engineering example，the bending moments and shear force of stabilizing structure are obtained through in-situ measurement. At the same time，the bending moments and shear force of stabilizing structure are computed by traditional method using Winkler elastic model. This paper presents an analysis and comparison of the in-situ measurement and numerical simulation. Through a series of case studies，the calculation results of FEM are close to the result of in-situ measurement. Some useful conclusions are obtained and suggestions are proposed. Such method offers a reference for evaluation of similar engineering in the future.

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KEY TECHNIQUE IN LANDSLIDE CONTROL AND ITS HANDLING MEASURES

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2005, 24 (21): -3818 doi:
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[PDF 513 KB] (1708)

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Landslide has become one of the factors which restrict the state economic development，especially in the western area of China，the landslide disasters are more serious owing to special landform and geological conditions. It often blocks traffic and river，destroys factory and mine and burries villages and towns and even results in a great loss of life and property. The author，based on experience and research for landslide control of 44 a and connected engineering geology with rock mechanics，presents several key techniques and its handling measures in landslide prevention so that it can provide reference to the technicians who are engaged in landslide disaster controlling. The main content concludes：(1) the problems existing in landslide control at the present；(2) key techniques and its handling measures in landslide prevention：① division of slice，grade and layer of large-scale and complex landslide；② slope structures and failure mode of landslide；③ survey and monitoring techniques of landslide；④ test and choice of shearing strength parameter of soil in the sliding zone；⑤ landslide prevention；⑥ basic principle for preventing landslide and its engineering measures.

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FOUR NEW TECHNIQUES IN SLOPE REINFORCEMENT

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2005, 24 (21): -3828 doi:
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Although there are many techniques for slope reinforcement，it isn¢t easy to utilize them economically or efficiently. Due to the deficiency of geological knowledge or some defects of reinforcement techniques themselves，some slope reinforcement projects are unsuccessful with huge economic losses and social problems. In view of the actualities of reinforcement techniques and great needs of project constructions in China and considering deficiencies of some available techniques for slope reinforcement，four new techniques in slope reinforcement are introduced in this paper，i.e.，the fiber bundle seepage-guiding drainage hole，prestressed anchoring beam，layered and reinforced stone-gabion retaining wall and prestressed anti-slide pile. Among the four new techniques，the first one is aimed at drainage hole jammed with soil and thin sand，and designed according to the idea that water can seep through the boundary surfaces between fibers，soil and thin sand. The second technique is developed to overcome some deficiencies of prestressed anchor-bars or anchor-cables. For example，anchor-bars or anchor-cables have smaller reinforcement scopes in some situations，and it is more difficult to adjust their anchoring forces under different geological conditions. Keeping main merits of general stone-gabion retaining walls (including convenient building materials and lower construction costs)，the layered and reinforced stone-gabion retaining wall is still characterized by higher reinforcement efficiency，in contrast to weaker linking strength and poor reinforcement effects of conventional one. Based on conventional anti-slide pile techniques，the prestressed anti-slide pile is developed with an aim of increasing its anti-sliding capability，which can be achieved by purposely placing one or several pre-stressed pillars near potential sliding planes of a slope. The fact should be noted that the above four techniques have been granted national invention patents.

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APPLICATION OF INTERVAL ANALYSIS METHODS TO SURROUNDING ROCK STABILITY OF DEEP ROADWAY ENGINEERING

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2005, 24 (21): -3835 doi:
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In stability design and mechanical analysis of surrounding rock for deep roadway，it is difficult to get a great deal of data samples and its interval range can be determined easily for those basic data which affect the stability of surrounding rock because of limit of information. It is also very difficult to determine distribution function and membership function. Physical and mechanical parameters of rock mass and support are regarded as interval variables and interval math is used to analyze mechanical state of surrounding rock. Therefore，interval analysis method is introduced and interval math is regarded as a solution of above-mentioned problem in the paper. Physical and mechanical parameters are expressed through interval variables，and some response functions of surrounding rock，for example pressure equation，are expressed by interval models. An output of the interval model is an interval value. A calculation program that is used to solve interval model is suggested and applied to analyze surrounding rock of deep roadway. The engineering example shows that interval approach has good adaptability and bright future in deep rock mass engineering field.

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EXPERIMENTAL STUDY ON CHEMICAL REINFORCEMENT OF RESISTING WEATHERING OF RED SANDSTONE

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2005, 24 (21): -3841 doi:
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The chemical reinforcement of rock mass is researched on the background of resisting weathering of surrounding rock at Longyou Grottoes in Zhejiang Province. Four layouts with four different chemical materials are applied in order to reinforce sandstone specimens in the laboratory. The new material of chemical reinforcement which is named CRS is put forward through the analysis of the parameters obtained from test. The CRS reinforcement test follows the principle that the voids in rocks are filled with products from the reaction between inorganic silicon and rocks first and then the rocks are dehydrated by reaction between organic silicon and hydroxyl in rocks so as to achieve the goal of reinforcement. The wave velocity，cohesion，peak strength with 5 MPa confining pressure increase 15%，50%，50% or so，respectively，and the variation of inner friction angle is not apparent after rock specimens are fully socked in the CRS material in the laboratory. The rock mass structure is apparently densified and the wave velocity of surrounding rock is increased by 10% for dry rock mass and 5% for rock mass soaked in water after the surface of grotto surrounding rock is treated by the CRS material in-situ. It is proved that the reinforcing depth is more than 3 cm. Until now for about one year the surface and inner color of rock mass has not yet obviously changed.

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REINFORCEMENT EFFECTS AND CONSTRUCTION KEY TECHNIQUES OF TWO-ENDED ANCHORS OF TGP SHIPLOCK

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2005, 24 (21): -3847 doi:
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According to the requirements of construction speed and high quality for the Three Gorges shiplock，the key technologies such as the drilling technology of the high accuracy cable holes，the key technology of the stressing and locking，the grouting technology of the two ended cables，are studied during the anchorage construction process；and the research results are applied in the anchorage engineering of the Three Gorges Project. In addition，the reinforcement effects for the two ended cables are studied by field tests. The results show that the compression zones are formed around the two-ended cables with radius of 2 meters and depth of 8 meters and the mechanical properties of the surrounding rock mass are effectively improved.

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ELEMENT MODEL WITH SHEAR BAND AND ITS APPLICATION TO PROGRESSIVE FAILURE ANALYSIS OF SLOPES

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2005, 24 (21): -3852 doi:
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An element model in which a shear band crosses through the element is presented. By way of the minimum potential energy principle in the element，the displacements of the new internal nodes which are produced by the shear band crossing the element boundary are related with the peripheral nodes of the element；thereby the equivalent stiffness matrix and equivalent load vector are obtained. And then put the shear band elements together with the other common elements to assemble the total stiffness matrix and total load vector. The progressive failure process is simulated by using the shear band element model and the automatic tracking procedure. The effects of the cohesion，friction angle and residual strength coefficients on the slide track and safety factor of slope are analyzed. The computing results show that the slide track obtained by considering the progressive failure is similar to the catenary but not to the circular arc，which is accordant with the results obtained from practical observation and theoretical analysis. The further studies show that the slide track is not only related to the stress and strength in the slope，but also related to the history of failure. The strength parameters have slight effects on the slide track，but have relative strong effects on the safety factor of slope.

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TBM JAMMING AND DEFORMATION IN COMPLICATED GEOLOGICAL CONDITIONS AND ENGINEERING MEASURES

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2005, 24 (21): -3858 doi:
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Integrative action from folding，faulting and squeezing of weaken rocks constitutes great challenge to normal function of tunneling boring machine (TBM). As a case study，the Shanggongshan tunnel for water transfer with a diameter over 3 m，located at the eastern blank of the Puduhe fold，southwestern China，was encountered squeezing，TBM jamming and plastic deforming of shields. Between chainages 4 km+340 m–439 m at a depth of about 200 m，where the sandy and argillaceous slates play dominant roles，together with a gentle dipping of reversed fault，a TBM is seriously jammed several times. Extra-excavation in both sides made the back shield seriously plastically deformed. This paper presents the analysis of its complicated geological background from mineral contents to mechanical properties，together with compression state of the shield from binary to uniaxial as progressive trial excavating for release of the shield. The squeezing of rocks and shield failure occurred more severely in the upper and right part of the tunnel cross-section. Actual measures as manual excavation outside of the shield，steel frame supporting and advanced adit for prediction were adopted. Adjustment of the tunnel alignment was carried out after this section encountered of more faults ahead of the working face. Previous unsuccessful case examples have made us carefully consider the suitability of TBM in complicated geological conditions.

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ANALYSIS AND EVALUATION OF SEISMIC REACTION
OF TYPICAL FOUNDATION SOILS IN XIAMEN

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2005, 24 (21): -3864 doi:
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[PDF 516 KB] (1137)

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In order to evaluate the seismic stability of foundation soil in Xiamen，earthquake reaction analysis for 4 typical sites were conducted using FEM and the way recommended by code for seismic design of buildings (GB50011–2001 of China) as well as shaking table test. The first site consists of a stratum of fill soil and two layers of sands as well as a layer of soft clay. The second site consists of only a stratum of fill soil with thickness of 10 meters. The third site is just a layer of soft clay with thickness of 26 meters. The fourth site is a middle-coarse sand containing some mud. The equivalent nonlinear constitutive model was adopted to describe the behaviors of various soils mentioned above. The pore water pressure model proposed by the authors was used to analyze the change of dynamic pore water pressure in the sand layers；The modulus softening method was applied to calculate the permanent deformation of the foundation soils. The sites were discreted by isoparameter element with 8 nodes. The dynamic reaction equations were solved with Wilson-θ method and frontal solution technique. Total of 20 cases were simulated numerically and analyzed including of three types of seismic waves (two kinds of natural earthquake waves of Xiamen and the earthquake wave of Songpan)，three peak accelerations of earthquake (i.e.，0.15，0.2，0.3 g)，4 intensity of static loads (i.e.，0，50，100，150 kPa). And the deformation fields，the pore water pressure fields，the seismic depression，the heave and the liquefaction grades for the four sites were obtained. The research results show that when strong earthquake takes place，the seismic depression of the fill foundation soil is not obvious and has small effect on the road of circle Amoy island. The seismic depression of the soft clay with large thickness is big；and failure patterns of the soft soil develops from local shear to general shear. The sand buried shallowly may be liquefaction. Above study results have an important consultation value to make aseismic decision of the foundation in Xiamen.

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APPLICATION OF COMPOUND SOIL-NAILED WALL TO FOUNDATION PIT IN SOFT SOIL

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2005, 24 (21): -3876 doi:
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[PDF 302 KB] (1141)

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The compound soil-nailed wall(CSNW) is a new style of support of foundation pit. This method is widely used in the project practice in recent years because of the excellent behavior and cheap cost. The styles of different CSNWS are introduced，and the research of the deformation mechanism and analysis of global safety of the CSNW employed in soft soil is emphasized. According to the observation of many CSNW projects，it is concluded that the process of crack development on the slope can be divided into three main phases，and the explanation for the cause of each crack phase is described. The countermeasure for dealing with each crack phase is recommended to secure the stability of the excavation. Two methods for calculating the global stability of the CSNW is introduced. One is the “double-circle” slice method，which is a modified method based on the traditional one. The proposition that the failure surface is composed of two circular surfaces is introduced. These two circular surfaces connect smoothly in the position of deep mixing pile. With this proposition，the anti-slide attribution of the soft clay in the passive region is considered properly. This method has already been employed to design a lot of CSNW project. Another method to calculate the global safety factor is shear strength reduction method. This method is getting more and more popular in the region of slope stability analysis. The region of CSNW，the strength of the interface between the soil and nail is not considered. A project calculated with shear strength reduction method is described. It is also pointed out that the method employed in gravity wall analysis is not suitable for CSNW.

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GLOBAL SAFETY FACTOR OF COMPOUND SOIL-NAILED WALL DETERMINED BY STRENGTH REDUCTION METHOD

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2005, 24 (21): -3882 doi:
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[PDF 632 KB] (1076)

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The strength reduction method and explicit finite difference method are used to calculate the global safety factor of the compound soil-nailed wall(CSNW). Compared with the traditional slice method，such as simplified Bishop¢s method，Janbu¢s method，Spencer¢s method and Morgenstern-Price¢s method，the strength reduction method reduces a lot of assumptions，such as the shape of the failure surface and the location of the failure band. Thus，the strength reduction method makes the concept of safety factor more clear and the failure surface more intuitive. In the calculation，only the strength of the soil and the cement deep mixing pile are reduced during the process. The strength parameters of the nail bar and that of the interface between the grouting body and the soil are regarded as constant. A compound soil-nailed wall project of typical soft clay of Shanghai is presented. The contour map of shear strain increment is recommended to recognize the failure surface or failure band of the CSNW. The failure surface calculated with strength reduction method is identical to the actual failure pattern of the CSNW. The traditional slice methods based on the limit equilibrium theory are also used to calculate the global safety factor. The result of strength reduction method and that of the traditional computing technology are compared and the difference between them is smaller than 10%. The tiny discrepancy of the safety factors calculated by the different methods mentioned above is acceptable. So it is concluded that the strength reduction method can be used in practice.

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STUDY ON ARCH ACTION AND EARTH PRESSURE THEORY FOR CULVERTS UNDER HIGH EMBANKMENT

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2005, 24 (21): -3887 doi:
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[PDF 274 KB] (1375)

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The principle of earth pressure and arch action variation with the height of fills and the boundary conditions are studied by model test. The results show that the earth pressures on the top of culvert increase nonlinearly and the arch action occurs as the fills on the culvert is up to a certain height. Because the fills on the culvert are different from the rock，the arch action above the high fill culvert has the characteristics of unstability and the earth pressure can partly transfer to the top of culvert. Based on the principle of earth pressure increase and the characteristics of arch action，a new theory，nonlinear earth pressure theory for the culverts under high fills，is presented. It is demonstrated by an example that compared with the other earth pressure theories，the nonlinear earth pressure theory is a more reasonable earth pressure calculation method for the culverts under high fills.

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LINING STRUCTURE TYPE OF SUBSEA TUNNEL AND ITS
SUPPORT PARAMETERS OPTIMIZING

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2005, 24 (21): -3894 doi:
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[PDF 464 KB] (1456)

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Subsea tunnel is different from land tunnel and sea water level changes slightly relative to subsea tunnel depth. Automatic drainage is not adopted for subsea tunnel because its two exits are higher than underwater segment. Great hydrostatic pressure loads on the second lining structure. Lots of lining types about domestic and overseas subsea tunnels are investigated. According to subsea tunnel characteristics，subsea tunnel design theory and method are presented. Considering the geology and hydrology conditions of certain subsea tunnel，three lining structure types are adopted such as U-shape，ellipse and circle shapes. These three lining structures are computed with finite element method. Some valuable conclusions are made as follows：(1) lining of horse shape may sustain much water pressure in the condition of limited drainage；(2) it is reasonable that lining of ellipse sustains geological stress in great water pressure；(3) it is the most reasonable that lining of circle sustains geological stress while lining of full impermeability is adopted in subsea tunnel.

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ON MODELING OF THERMO-MECHANICAL VOLUME CHANGE BEHAVIOR OF SATURATED CLAYS

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2005, 24 (21): -3903 doi:
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[PDF 240 KB] (1691)

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Problems related to temperature are attracting more and more attention in civil engineering (buried pipeline stability)，energy storage (natural gas storage) and high level radiation waste disposal etc.. Better understanding of the thermomechanical behaviour of the materials subjected to temperature effects is a key issue for the analysis of this kind of applications. A multi-mechanism thermo-mechanical model for saturated clays is presented. For the description of the loading behaviour，the yield surface proposed by Picard (1994) was adopted (LY for loading yield). For the heating- cooling behaviour，a new mechanism TY (thermal yield) was introduced，which，together with a third mechanism HC (heating collapse) corresponding to the expansion-contraction change locus，allows for the description of the elastoplastic behaviour observed with temperature changes in clays. Coupling between TY and LY was taken into account in order to describe the thermo-hardening phenomenon observed experimentally (Towhata et al. 1993，Sultan 1997). The performance of the model was checked by carrying out a qualitative test-heating a slightly over consolidated soil，and the simulation of Sultan¢s experimental results on Boom clay (1997).

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PREDICTION OF GROUND HEAVES IN EXPANSIVE SOILS BASED ON CONSOLIDATION TESTS

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2005, 24 (21): -3911 doi:
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Consolidation tests are applied to determine the indexes of volumetric deformation with respect to normal stress for expansive soils in Guangxi of China，and to predict ground heaves in expansive soils. Static cone penetration tests are conducted for expansive soil investigations，and test results are used to determine the active expansive zone. A theoretical solution is developed to determine cracking depth of expansive soils. The depths of the active zone from static cone penetration tests and theoretical solution are respectively identical to the results from observation in-situ. A simplified method for prediction of ground heaves in expansive soils based on consolidation tests is given. The index of ground heave in expansive soils is used as the basis for the classification of expansive soil foundations. The results of expansive ground heave have significant meaning to the choice of building foundations in expansive soil.

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RESEARCH ON INFLUENCE OF SOIL CORE ON LOAD BEARING CHARACTER OF LARGE-DIAMETER TUBULAR PILE USING CAST-IN-SITU CONCRETE

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2005, 24 (21): -3916 doi:
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[PDF 288 KB] (1159)

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Owing to the complexity of soil core character，the calculation of bearing capacity of tubular pile isn¢t mature and the operation mechanism of single pile bearing capacity is not clear yet. A test study example is introduced and the Q-S curve is gotten from the test. From two aspects of soil core height and its mechanical characteristics，the influence on load bearing character of large-diameter tubular pile using cast-in-situ concrete is studied. According to whether the top soil core bears load or not，the tubular pile structure is classified into two types to analyse the mechanism of inside friction. The reason for the occurance of inside friction is that the relative displacement or the trend of it exists between the soil core and pile. By assuming that the inside friction changes in minus exponential function，the method for load distribution between inside wall of pile and the top soil core is established. The result indicates that the core contributes much to enhance pile bearing capacity and to decrease pile settlement. At last，the calculation formula of vertical bearing capacity of tubular pile is established，which is proved to be practicable in projects.

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STABILITY CALCULATION METHODS FOR
GRILLAGE SUPPORTING STRUCTURE WITH PRESTRESSED
ANCHOR AND ITS APPLICATION

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2005, 24 (21): -3922 doi:
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[PDF 339 KB] (1425)

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Based on the failure mode of the slip surface and the theory of limit equilibrium，using the circular slice method，and considering the supporting structure and anchor effects on stability of soil slope，the search model for the most dangerous slip surface is set up；and the function relationship between stability factors and the center of circular slip surface is derived. By setting the center zone of slip surface dynamically with computer，and searching the center of slip surface by the method of lattice in the center region，a method of the stability calculation for the grillage supporting structure with prestressed anchor is given. Finally，the calculation software is developed and applied to a practical case.

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EXPERIMENT ON MECHANISM OF SLOPE FAILURE OF DEBRIS FLOW FAN AND STABILITY ANALYSIS

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2005, 24 (21): -3927 doi:
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Failure of debris flow fan is distinct from the common rock and soil slope failure due to the unique geotechnical features of debris flow sediment. Unfortunately，this type of failure was not comprehensively and systematically studied in the past. In our recent research，according to the unique characters of debris flow fan the Spencert slicing method with varying side force inclination is used to search for the noncircular critical slip surface. This is done using Spreadsheet-automated constrained optimization. The results are then compared with the in-situ slip surface. A practical subroutine is developed to interpret the stability of slope with varying physical parameters along the depth by using Visual Basic Application embedded in Microsoft Excel. The in-situ experiment shows that the water content hardly change 50 cm beneath the slope surface and no obvious tension cracks are observed behind the slope. However in the soil layer where the actual sliding occurred，great alteration of water content under concentrated artificial rainfall happened，which is in consistent with the results of numerical simulation. With the increase in height of the soil layer，the calculated safety factor gradually decreases and an optimized noncircular slip surface with an average height of 2.4 m is obtained satisfying all the constrains and assumptions. It can be inferred that the slope failure of the debris flow fan is attributed to the dynamic seepage force caused by hydraulic gradient；and the slicing method is not suitable for the research of the mechanism of failure of debris flow fan.

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RESEARCH ON DEFORMATION AND SUBSIDENCE CHARACTERS OF GROUND AND SURROUNDING ROCK INDUCED BY UNDERGROUND MINING UNDER THICK COVERING TERRAIN BY MODEL TEST

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2005, 24 (21): -3935 doi:
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[PDF 369 KB] (924)

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Based on the prototype of the mine，by applying the physical simulating test，not only the ground¢s deformation and subsidence characters but also the wall rock¢s deformation and failure characters around the goaf are analyzed deeply. In the meantime，the failure mechanism of the wall rock around the goaf，the time effect characters of the wall rock¢s deformation and the ground¢s deformation and subsidence. Compared with the some corresponding numerical simulating results (2D，3D elasto-plastic FEM，2D discrete element，etc.)，that the physical simulating result is more accurately close to the in-situ monitoring result than that of the numerical simulating results，is discovered. Some new revelatory realizations that could not be obtained from many numerical simulating methods are obtained from the test. The optimum original-mining depth and some new realizations from the results of the test are accepted and adopted by the mining company. It makes significant directive role in the real engineering.

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RESEARCH ON DEFORMATION AND SUBSIDENCE CHARACTERS OF GROUND AND SURROUNDING ROCK INDUCED BY UNDERGROUND MINING UNDER THICK COVERING TERRAIN BY MODEL TEST

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2005, 24 (21): -3935 doi:
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[PDF 369 KB] (899)

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Based on the prototype of the mine，by applying the physical simulating test，not only the ground¢s deformation and subsidence characters but also the wall rock¢s deformation and failure characters around the goaf are analyzed deeply. In the meantime，the failure mechanism of the wall rock around the goaf，the time effect characters of the wall rock¢s deformation and the ground¢s deformation and subsidence. Compared with the some corresponding numerical simulating results (2D，3D elasto-plastic FEM，2D discrete element，etc.)，that the physical simulating result is more accurately close to the in-situ monitoring result than that of the numerical simulating results，is discovered. Some new revelatory realizations that could not be obtained from many numerical simulating methods are obtained from the test. The optimum original-mining depth and some new realizations from the results of the test are accepted and adopted by the mining company. It makes significant directive role in the real engineering.

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PRESSURE-DISPERSIVE ANTI-FLOAT ANCHOR TECHNIQUE AND ITS APPLICATION TO ENGINEERING

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2005, 24 (21): -3948 doi:
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Combining a practical case，the technique of pressure dispersive anti-float anchor on experiment，design，construction and examination is studied. The pressure-dispersive anchor，especially the U-shaped anchor surrounding load body has good endurance，high anchor efficiency，and advantage of stress and deformation coordination of the underground structure and reduces the structure-building price. It has obvious technique advantage as the permanent anti-float anchor. Only at design tensile load does each unit of the pressure-dispersive anchor undertake the same tensile load；the identical load and synchronous tension method should be adopted to tension test of pressure-depressive anchor.

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STUDY ON REINFORCEMENT OF MICRO-PILE AND ROCKBOLT FOR AN UNSTABLE HIGH-STEEP ROAD CUT SLOPE

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2005, 24 (21): -3954 doi:
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[PDF 238 KB] (1164)

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A landslide at the deep-seated weathered road cut rock slope，is recorded at the section of K97+900～K98+500 of Louyang-Sanmenxia Expressway in Henan Province. Based on the failure mechanism analysis of this high-steep road cut slope，a comprehensive reinforcement design has been done，including prestress rockbolts，micro anti-slipping piles，retaining wall，sprayed concrete and high-pressure cement grouting，in which，an initiative reinforcement method of anti-slipping micro-pile instead of the ordinary pile and the high-pressure cement grouting to reinforce the slip surface are used. Both can improve the stability of the slipping rock. Considering the different properties of reinforcement structures，a numerical model of Lagrange finite-difference has been used to analyze the stability of slope and the bearing capacity of the reinforcement structure. Both the modeling analysis result and the engineering application show that the combined reinforcement structures can ensure the stability of the unstable high-steep road cut slope.

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STUDY AND APPLICATION OF COMPLETE ROCK BOLTING TECHNOLOGY TO COAL ROADWAY

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2005, 24 (21): -3959 doi:
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[PDF 270 KB] (1758)

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Rock bolting technology has already been used universally and created prominent technological and economic profit. This paper introduces the new research achievement of rock bolting technology for coal roadway. In rock bolting theory，it is considered that the main function of rock bolting is to control dilatancy and destroy in bolted surrounding rockmass，such as delamination，sliding and fracture opening，to maintain the completeness of surrounding rockmass to maximum extension，and to avoid harmful deformation. The technical parameters and operation methods of the geomechanics instruments are introduced，including small borehole hydrofracturing stress measurement device，wall rock strength measurement device and fiber borehole observation rig. The contents and characteristics of dynamic and informational rock bolting design method，computer design software for engineers and technicians in coal mines are discussed. The mechanical properties of high strength rock bolting materials，such as rock bolts，resin capsule，W-shaped strap and cable bolts are analysed. Finally，the rock bolting effect is evaluated through monitoring data in a case study. It is proved that the rock bolting is the most suitable supporting type for coal roadways in coal mines with high efficiency and low cost.

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PREDICTION AND COUNTERMEASURE FOR ROCKBURST
IN CANGLING MOUNTAIN HIGHWAY TUNNEL

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2005, 24 (21): -3965 doi:
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[PDF 367 KB] (1413)

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Based on the engineering geology and the measured geostress，the initial stress field is obtained by inversion. Then the circumferential stress after excavation is calculated by FEM. According to the results and combined with laboratory rock test and different judgement criteria of rockburst，the conclusion is got that the low middle class of rockburst will occur in the survey and design plases；and some countermeasures are proposed. In the construction phase，for prediction of rockburst with more precision，the general rockburst condition is predicted again combined with the real situation；and the result shows that the low-middle class of rockburst diminishes correspondingly. Meanwhile，the rockburst 300–500 m in front of the cutting face is predicted by stages according to the measured geostress；and the Lusen criterion is found to be applicable.

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LABORATORY STUDY ON FRACTURE TOUGHNESS KIC OF COMPACTED CLAY

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2005, 24 (21): -3972 doi:
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[PDF 283 KB] (1094)

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It is widely accepted that the linear elastic fracture mechanics (LEFM) can be used to investigate the induction and propagation of cracks in soil，especially for over-consolidated and hard clay，but no method is acknowledged to be perfect to determine fracture toughness KIC of soil in laboratory. In conventional three-point bending beam test，the single edge cracked beam (SECB) may be fractured only due to gravity itself. Even if no fracture failure of specimen occurs before test，the influence of the gravity of the specimen on test results can not be ignored because it is not little enough compared with fracture load. In this study，an improved method of three-point bending beam loading test is suggested，which can avoid the fracture failure before test and remove the influence of the gravity of the specimen because the loading direction is horizontal. Based on the improved method，an apparatus to determine fracture toughness KIC of soil is developed. The apparatus does have very simple structure，but its operation is very easy and its test result is reasonable enough. Using the improved testing method and the new apparatus，the fracture toughness KIC of compacted clay which is used to build the core wall of a high rock-fill dam in West China is investigated. The reasonability of LEFM used to describe the characteristics of the clay in the course of fracture failure is testified. The influences of dry density and water content in testing of specimen on KIC are also investigated. For the specimens which are made under the same water content，the values of KIC increase with the increase of the dry density. But for those that are made under both the same water content and dry density，with the variation of water content in test a maximum value of KIC appears.

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NUMERICAL ANALYSIS OF PRESTRESSED ANCHOR FLEXIBLE RETAINING METHOD

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2005, 24 (21): -3978 doi:
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[PDF 381 KB] (1322)

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A new retaining method for deep excavation-prestressed anchor flexible retaining method has been developed by the authors. This technique is studied by finite difference method；and the calculating results are compared with the soil-nailed support system. Critical slide zone of deep excavation is controlled by prestress values. Based on the modified bar system finite element method，the prestressed anchor flexible retaining system is calculated and analyzed through a practical engineering. The distribution rules of horizontal displacements and anchor axial force are calculated. By the numerical analysis，its advantages such as small displacements and application to super-deep excavations are investigated.

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LAYOUT AND MONITORING-CONTROLLING DESIGN OF UNDERGROUND OPENINGS AND TUNNELS FOR LONGTAN HYDROPOWER STATION

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2005, 24 (21): -3983 doi:
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[PDF 374 KB] (1162)

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Longtan Hydropower Station is a large water conservancy project including electricity generation，flood control，navigation and so on. Layout of the large underground openings and tunnels and its geological conditions are described briefly. Besides，a monitoring-controlling design problem of the underground openings and tunnels is discussed. Monitoring results show that the surrounding rock of the underground openings and tunnels is stable and its design is reasonable.

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ANALYSIS OF MULTI-ROW OF PILES AS BARRIERS FOR ISOLATING VIBRATION IN FAR FIELD

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2005, 24 (21): -3990 doi:
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[PDF 367 KB] (1215)

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Based on the integral equation of Rayleigh wave scattering，piles are treated as irregular obstacles in elastic half-space. This paper presents three-dimensional multi-row piles as ground barriers for passive isolating vibration in far field for the first time. Effects of relevant parameters on the effectiveness of vibration isolation are analyzed and presented. The theoretical results demonstrate that the rows of piles as discontinuous barriers can be functioned as an integrated system to isolate ground vibration. The number of row mainly determines the thickness of barrier system，which affects screening effectiveness. The cross-section size of each pile may have less effect on the vibration isolation. The screening effectiveness by rows of small cross-section piles densely arranged can be as good as that of the open trench and in-filled trenches. The space between the pile rows may have less effect on the vibration reduction. The net spacing between piles along each row can be an important factor for the vibration isolation；it can be determined by the practical engineering. In order to obtain satisfied effectiveness of isolating vibration of the rows of piles as discontinuous barriers；the distance between piles in a row should be controlled close enough. At last，a case history proves the good isolation effect by rows of piles. The method and findings presented are useful in the design of ground barrier and can be used to predict the functions of rows of piles as barrier system for ground vibration.

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SYNTHETICAL CONTROL TECHNIQUE AND ENGINEERING APPLICATION TO ROADWAY WITH FALSE-HARD ROOF HIGH SURROUNDING PRESSURE AND WATER DISTURBANCE

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2005, 24 (21): -3996 doi:
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[PDF 355 KB] (1124)

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The composition of the roof rock has a great influence on the stability of the roadway surrounding，especially for those roadway with the false-hard roof，which will be easily weathered or be weakened when encountering water. The composition of the false-hard roof rock sampled from the 7244 working face was determined with the X-ray diffraction experiment. The mineral composition of the false-hard roof was obtained. The results explain why the roof rock strength becomes weak encountering water or weathering. The inherent mechanism of the loss of the prestressed bolting and loosening between bolts and surrounding rock was analyzed. On the basis of these analysis，the conclusion that the key technique is water control in such condition is proposed. False-hard roof can turn into true-hard roof when no water invading. Based on the supporting technique system of the high strength and high prestressed bolting，rock grouting and surface guniting can decrease or even avoid the water influence on the bolts，surrounding rock and coal. At last，a comprehensive measure，named three zones-three roofs-three supporting techniques，has been put forward and applied successfully in the 7244 roadway. This technique can be used in the similar roadway supporting.