Solid material develops from elastic to plastic then to failure after undertaking some load，which means that yield is different from failure. The system of yield criteria for geomaterial is discussed and two definitions which are point failure and surface failure in stress field are put forward. And the criteria of surface whole failure is defined through traditional limit analysis method. Simultaneously，the deficiencies for traditional limit analysis and numerical analysis are pointed out by reviewing and analyzing the solution characteristics of traditional limit analysis method. Based on the combination of these two methods，a newly developed numerical limit analysis method is built，which has enlarged the application rage of limit analysis. The significances and features of traditional limit analysis method and numerical limit method are studied，as well as the reliabilities. The advantages and disadvantages of numerical limit analysis are listed；and the wide applicability of numerical limit analysis in the slope(landslide) engineering，foundation engineering and tunnel engineering is illustrated.

The law of opening-mode crack initiation and the evolution of crack tip stress intensity factor were detected considering the combined action of seepage pressure and far-field stress. Accordingly，the damage fracture mechanical model of rock-like material and the evolution equation of the crack tip stress intensity factor were proposed for pre-cracking rocks under the combined actions of compression-shear field and seepage field. The crack tip stress intensity factor was advised to be used as a criterion for judging the degree of rock crack initiation. The results show that：(1) Open crack tip stress intensity factor is influenced by confining pressure，seepage pressure，crack tip radius of curvature，as well as crack inclination angle. (2) Little change is observed in the cracking angle，which maintains about 70.5° with the pre-crack angle varying. (3) The cracking strength is inverse proportion to the seepage pressure，crack length and the crack tip radius of curvature，while in direct proportion to the confining pressure. Also the crack angle is responsible for the crack strength. The case studies indicate that the uses of different crack initiation criteria all lead to an identical tendency that the crack initiation strength decreases with the increase of the seepage pressure. The laws that the crack initiation strength is inverse proportion to the seepage pressure and proportion to confining pressure are further verified by conducting experiments under various experiments. When the crack angle is 30°，the crack initiation strength is maximal，the crack angle of 60°    next and 45°    last. It is worthwhile to pay attention to the fact that increasing the seepage pressure would result in the decrease of the crack initiation strength，enlightening the prospect of easier ore extraction under high stress by hydraulically induced cracking.

The section from Wulidian to Shanyanggou Reservoir Station in Chongqing Transit Line 6 is the testing project，in which the tunnel boring machine(TBM) was firstly employed as a tool for the construction of urban rail transit. To investigate the stability of the surrounding rock of tunnel in construction，a large number of in-situ monitorings were conducted. Based on the monitoring data，the variation laws and distributions of the vault settlement，displacement in deep surrounding rock，axial force in bolt，internal force in steel arch and contacting stress with surrounding rock were analyzed in detail. Then，the supporting parameters optimization was accomplished using numerical simulation. The research is beneficial to fundamentally guide the follow-up construction of the tunnel and the design scheme optimization. The proposed technique has potential applications to a large range of urban construction engineerings using TBM technology.

After decades of exploitation in Jinchuan mine，mining depth has reached to 1 000 m. Due to complex geologic condition，high geostress and high hydraulic pressure，the stability of deep mining engineering is a crucial problem. A large number of field geological surveys of 850–1 000 m level in Jinchuan No.2 mining district are carried out. Physico-mechanical parameters，expansion and softening properties of deep typical rock are measured. The change laws of rock mechanics and geostress with mining depth are analyzed. By using geological mechanics(RMR) classification method and rock quality(Q value) classification method，zone maps for quality classification of rock mass in Jinchuan No.2 mining district are plotted. Based on the deep surveys of deformation and failure characteristics in deep roadway in Jinchuan mine，the stabilities of deep roadway excavation and supporting under high geostress and high hydraulic pressure are studied. The result shows that coupled U steel-anchor supporting technology performs best. By summarizing the practice experience of supporting technique in deep roadway in Jinchuan mine，some new ideas on deep roadway excavation and supporting technologies are put forward. The influence of different extraction methods on the stability of surrounding rock and backfill at depth is investigated. By optimizing the sequence of panel mining stope of ore block，the mining sequence of the “three stope panels”is applied to the mine，which has obvious effect on controlling the displacement of surrounding rock and backfill.

As hydro-fluctuation belt is the sensitive area of bank slopes，the change law of fracture toughness under the fluctuation of reservoir water level is crucial to the bank slope stability. According to the actual occurrence environment of hydro-fluctuation belt，taking typical sandstone in the Three Gorges Reservoir area as the research object，long-term soaking and immersion-air dry circulation test schemes are designed. The test results show that：(1) Sandstone samples have obvious softening trend under long-term soaking and immersion-air dry circulation. The degradation trends of fracture toughness，tensile strength and compressive strength of sandstone are consistent basically；and the degradation rate is relatively obvious in initial stage，later gentle. (2) The degradation trends of parameters are quite different. And the fracture toughness is the fastest，tensile strength is the second，and compressive strength is relatively slow. (3) Comparing the two schemes，the degradation trends of mechanical parameters of sandstone show more apparent under immersion-air dry circulation，which shows that the action of immersion-air dry cycle can not be ignored in simulating the hydro-fluctuation belt′s water-rock interaction. The research results have important reference value for analyzing the stability of bank slopes exist in reservoir area，and relevant test methods can also provide reference for similar tests.

Seismicity in mines is dynamic response of rock mass to mining and reflects the stress state，deformation and destruction of rock mass. Using the time history methods of the cumulative apparent volume ?VA，energy index EI and cumulative volume of production ?Vm，the relationship between seismic deformation and mining rate is studied in the framework of quantitative seismology with the seismic data monitored in Donguashan Copper Mine. According to the view of storage and release of energy，combining with seismic apparent volume VA and elastic convergence volume VE，the ratio of the cumulative apparent volume ∑VA to the cumulative volume of production ?Vm is defined as coefficient of seismic response to mining(CSR) to present the relationship between energy storage and energy release in rock mass. The results show that，the volume of production influences obviously on time history curves of ?VA and EI；there is a correlation between mining rate and seismic strain rate；the variation of CSR indicates the tendency of stability of rock mass system，which can be easily used in analysis of mine seismicity monitoring and as a good guide parameter to control mining rate.

The critical failure characteristics of sandstone experiencing change stresses from three-dimensional loading to confining stress unloading and to axial impact，are investigated by the improved split Hopkinson pressure bar(SHPB) with axial static pressure and confining pressure. The results show that：(1) The critical failure characteristics of sandstone under external impact is influenced obviously by axial static pressure；and the impact strength first increases and then decreases as the axial static pressure increases. (2) The stress-strain curve of sample under coupled static and dynamic loading is a typical class I curve when without axial static pressure and the axial static pressure is 20% of uniaxial compressive strength. (3) With the increase of axial static pressure，the stress-strain curve changes to the typical class II curve gradually. In the failure process of sample，the energy change law is from disturbed energy absorption to elastic stored energy release，which can reflect the mechanism of interactions between high static stress and dynamic disturbance in the process of rockburst. The results can provide a test support for the further research of rockburst mechanism. The surface displacement field is monitored by digital speckle correlation method(DSCM). The surface displacement field results show that the samples present whole expansion characteristics under conventional impact loading；but under the axial static pressure of 72 MPa，the samples present the interaction of tension-shear failure and expansion failure，which reflects the effect of axial static pressure on the fracture mode of dynamic failure surface of sample.

Crushing tests of brittle rock(granite) under different dynamic and static loads are conducted on multi-functional static-dynamic coupling loading testing apparatus. The acoustic emission system AEwin is applied to collect the acoustic emission data in the rock crushing process. Based on the measured data，the relationship between total acoustic emission energy and rock crushing volume under different loading patterns is analyzed. The rock crushing volume and rock-breaking specific energy are used as parameters which can characterize the rock breaking effect to synthetically analyse the effect of rock fragmentation under various kinds of loading patterns. The results show that：(1) There exists a close correlation between the total acoustic emission energy and crushing volume，and the relation of acoustic emission energy per breaking volume under dynamic loading，static loading and static-dynamic coupling loading is WD＜WS+D＜WS，where，WD，WS and WS+D are the acoustic emission energy per breaking volume under dynamic loading，static loading and static-dynamic coupling loading，respectively. (2) The total acoustic emission energy and crushing volume under static-dynamic coupling loading are more larger than that of dynamic loading or static loading；and there is an optimal loading combination which can make the total acoustic emission energy and rock-breaking volume both reach to the maximum but the rock-breaking specific energy to the minimum.

The present contribution is concerned with theoretical and numerical issues in finite element slope stability analysis. In the theoretical part，instability phenomena of slope material are studied within the framework of bifurcation theory. It is proved that strain localization not only is a ubiquitous feature of elastoplastic geomaterials，but also is the unique instability mode of the elastic-perfectly plastic material with an associative flow rule under plane strain and plane stress conditions. The shear band coalescence criterion is proposed，which argues that slope failure occurs when smaller size shear bands coalesce into a dominant shear band which completely divides the slope into two parts. In the numerical implementation part，a strategy for tracking the localization band path is presented. By tracking the initiation，growth and coalescence of localization zones in terms of the localized state of all soil elements at each time step，the limit equilibrium state can be directly judged；and the critical slip surface can be simultaneously determined. Finally，the feasibility and reliability of the proposed criterion are validated by strength reduction and over-loading examples.

The mechanical response and unloading mechanism of rock are the key issues to evaluate and control stability for rock mass engineering excavated under high geostress. Based on the unloading confining pressure tests with triaxial high stress under conditions of different unloading rates and different initial confining pressures，combining the fractal theory and energy principle，the distribution rule of rupture fragmentation of marble specimens and its correlation with strain energy transformation are investigated. The characteristics of fragment fractal of marble specimens fractured is obvious locality under unloading confining pressure with triaxial high stress；and only in the range of sizes which is smaller than a certain features scale(fractal feature sizes threshold)，it presents good fractal property. The fractal dimensions of all fragmentation are greater than 2 in the test. The fractal dimension monotonously decreases with unloading rate increasing；and the influence of initial confining pressure on it closely relates to the unloading rate. Comparing with conventional triaxial compression test specimens，the dissipation and storage strain energies of rock specimens under high confining pressure near peak point are much smaller；but the rates of strain energy transformation before and after peak point under high confining pressure are much larger；especially the rates of elastic strain energy release and strain energy dissipation by confining deformation. The unloading rate is faster and the initial confining pressure is higher，the time of damage before peak and whole crack rupturing after peak are shorter；the dissipation strain energy and storage elastic energy are larger；the transformation rate of energy before and after peak is faster；the threshold of characteristics size of fractal for broken rock sample is bigger；the fractal dimension is smaller and tensile fracture is more obvious.

The tests for permeability of rock-like sample with filling fractures under high confining pressure and hydraulic pressure are carried out. Based on the ratio test，the specimens simulating sandstone are made；and the tests are made by self-developed triaxial instrumentation. From the results，it is found that：(1) The permeability coefficients of different filling fractures specimens are different；but they are always in the same magnitude under different confining pressures. (2) The permeability coefficient shows downward trend with the increase of confining pressure. (3) The geometrical characteristic of permeability structural surface is one of main factors influencing permeability of sample；(4) Permeability law of sample should be based on the test results.

According to the key technical problem of deep mudstone failure under drilling fluid soaking，the weakening law of strength is analyzed by the laboratory test；and the changing mechanism of core samples is analyzed through microcosmic angle. The result shows that：(1) Under the drilling fluid soaking，the mudstone strength increases first and then decreases with increase of coring angle. The decreasing range of strength is up to 49.5%–54.7%. With the increase of confining pressure，the increasing range of strength is lower and it is only 26.4%–39.2% with coring angles of 0°and 90°. (2) The elastic modulus of mudstone decreases with the increase of soaking time，and increases first and then decreases with the increase of coring angle. But the change law of the Poisson's ratio is opposite with that of the elastic modulus. (3) Comparing with the internal friction angle，the change of mudstone cohesion presents stronger regularity. The decreasing range of cohesion is larger with coring angles of 0° and 90°，and it reaches 67.3%；but the change range of cohesion is small under other coring angles. (4) Because of the invasion of drilling fluid，the stress intensity factor of crack at the tip increases；the critical fracture toughness decreases and the cracks propagate，which is the basic reason for strength decrease of mudstone. Simultaneously，mineral composition of the fitting in bedding surface is changed by the action of drilling fluid. So，the friction factor crack face decreases and the decrease of mudstone strength is intensified.

The cross-sectional internal force distribution and longitudinal dynamic response characteristics of tunnel through fault fracture zone under seismic load are studied with both dynamic numerical analysis and shaking table model test. Results show that：(1) The condition of surrounding rock is the important factor affecting the internal force of tunnel liner caused by earthquake. The worse surrounding rock conditions are，the more remarkable internal force caused by earthquake produce and the worse seismic performance represent. (2) In the transverse direction，the position of conjugate direction of 45°     is the most unfavorable tunnel seismic position；and the maximum internal force in tunnel lining is at the position under different conditions of surrounding rock. (3) In the longitudinal direction，when the tunnel traverses the interface between surrounding rock and fault，the internal force in tunnel lining caused by earthquake increases rapidly. (4) When the tunnel is far from the fault along the longitudinal direction，the internal force of tunnel tends to be a steady value. The research results can provide reference for seismic fortification of tunnel through fault fracture zone.

By analyzing the mechanism of rock burst start-up，the blasting effect of the concentrated stress distribution in the roadway is studied by numerical simulation methods；and the dredging method of pressure with deep-hole interval blasting based on theory of rock burst start-up is proposed. The research results show that：(1) The interval of deep-hole blasting in roadway should be the area of rock burst start-up，otherwise it will play a negative role. (2) It is limited to dredge and debase concentrated stress by increasing intension of roadway support. (3) On one hand，the dredging method of pressure with deep-hole interval blasting can dredge and debase the degree of concentrated stress or energy of the area of rock burst start-up，thus the rock burst start-up step can be prevented. On other hand，it let the area of rock burst start-up firstly move to the deep coal wall；and the total energy which is consumed by rock burst start-up in dredging pressure area increases，but the energy release speed reduces. The good effect of application the research results to field engineering is got.

Geological hazard accidents induced by excavation occur frequently in the course of tunnel constructions. In order to ensure tunnel construction safety，geological prediction for exploring potential geological conditions in front of tunnel face is widely adopted. Therefore，it is of vital importance to explore how to improve the interpretation level of geological prediction. Based on the characteristics of ground penetrating radar(GPR) signals in tunnel geological prediction，the Hilbert-Huang transform(HHT) method is used to extract instantaneous profiles of each IMF(intrinsic mode function) component in the original image and instantaneous parameters of the single trace signal，such as instantaneous amplitude，instantaneous phase and instantaneous frequency. The results show that instantaneous parameters decomposed by HHT method highlight the characteristics of the original signal，which can qualitatively identify the position and shape of catastrophic geological body，and improve the accuracy and credibility of the original image interpretation of ground penetrating radar.

The stability research on underground space project such as mining is always a popular issue in geotechnical engineering. Based on the analysis and summary of the research achievement of underground structure stability at home and abroad in recent years，an organic combination of the mathematical analysis method，experience analogy method，similar model test method，a numerical simulation method and field monitoring method is tried；a comprehensive analysis method for researching on underground artificial structure stability is put forward. The comprehensive analysis method is applied to engineering practice；and realization of feasibility of mining safety and high-efficiency stoping through the mining environment under the condition of loose and fractured ore rock is discussed. The research result shows that this comprehensive evaluation method is feasible and practical，so as to provide scientific reference for such complicated problems.

Rock quality designation(RQD)，which plays an significant role in the rock mass analysis，is an important parameter in geotechnical and geological engineering. However，the size effect and spatial effect have not been comprehensively considered. To investigate the spatial effect of RQD，three-dimensional(3D) fracture network modelling is used to simulate the actual rock mass，and numerous scan-lines are set to obtain RQD values. The result shows that the RQD values vary in different regions and have obvious spatial effect. To obtain the characteristics of RQD that could represent the whole rock mass quality，the analysis based on plenty of RQD samples should be conducted. In addition，to better reflect the inhomogeneity feature of rock mass，RQD ranges of different thresholds are studied；and the optimal threshold of 4 m that can comprehensively reflect the inhomogeneity feature of the investigated rock mass is determined. The size effect is an important feature of RQD. To investigate the feature，the RQD variation is researched by changing the scan-line length. The models and equations(i.e. A-A model，T-T model，A-A-S model，Priest-Hudson equation，and Senz-Kazi equation) are proposed and summarized. The size effects of different models are studied. The results show that：the error of size effect can be decreased using A-A-S model；when the threshold is relative large，the results by Priest-Hudson equation and Senz-Kazi equation have errors；and the RQD value based on 3D fracture network is more correct.

The shortages of Mahalanobis distance discriminant method and analytic hierarchy process are improved；and the improved distance discriminant analysis method is applied to the classification of surrounding rock mass by TBM tunneling in west route of South-to-North Water Transfer Project. The standard of surrounding rock mass classification cut by TBM is divided into four classes according to the characters of TBM tunneling and some corresponding research results. The improved distance discriminant analysis model of surrounding rock mass classification of tunnel by TBM tunneling is established，which considers five indexes，that are rock strength，petrofabric characters，the distance of structure faces，the included angle between structure face and tunnel axis and quartz content. The linear discriminant functions are obtained by training with a large of case data which come from Duke River-Make River reaches in west route of South-to-North Water Transfer Project. And the classification of waiting discriminant samples is carried out with the discriminant functions. At last，the judged results of improved distance discriminant analysis method are compared with the results of traditional Mahalanobis distance discriminant method，RTBM(rating of TBM) method and RMR(rock mass rating) method. The effectiveness of improved distance discriminant analysis method is verified. The research results show that the improved distance discriminant analysis model has many advantages，such as high prediction accuracy，and provides a new effective method for surrounding rock mass classification of tunnel by TBM tunneling.

In the full-scale model test of sand-flow method，time-history curves of sand-deposit radius，water pressure in the sand-flow system and the one under the model board are obtained under the conditions of different bottom surface materials of immersed tunnel. The analyses show that quadratic relationship exists between sand-deposit expansion trend in each direction and time under different bottom surface materials. Sand-deposit expands faster and has a better balance and fullness under the smooth material condition，with the maximum radius of 879 cm and the fullness of 99.3%，which is slightly higher than the one under the rough condition. It is feasible to increase the designed radius of sand-deposit to simplify construction. Material conditions and sand-deposit expansion do not have an effect on the water pressure of system except the one under the model board.

According to problems of different dimensions stones mining of many engineering requirements，on the background of the Tielu port quarry，the site investigation，engineering test，mathematical model prediction and blasting control technique are used to study efficient blasting mining techniques. Before construction，the blasting area is divided into different sizes stones in the mining region according to investigating result and blasting crater test，drawing fragmentation map of different sizes stones mining and improving the efficiency of the specifications stone mining. With Kuz-Ram mathematical model，the relation between the blasting design parameters and the percentage of different sizes block stones after blasting is established. Based on the relation，blasting fragmentation and blasting effect can be predicted by blasting parameters. Simultaneously，the blasting parameters are optimized by the prediction results. The decoupling and nonuniform charge collapse blasting to reduce the rate of ore powder is studied during construction；and the mechanism is analyzed. The collapse blasting of the decoupling and nonuniform charge structure can reduce the ore powder and cost，by comparing the blasting effects of coupling charge，the hole charge and the decoupling and nonuniform charge structure. The field application shows that these techniques can meet the engineering requirements and bring economic benefits.

The glass fiber reinforced polymer(GFRP) bar is a new reinforcement material composed of glass fiber and resin，and has good application prospects. The GFRP bar has the properties of anisotropy. Its horizontal compressive strength far less than axial tensile strength；and it has remarkable size effect. Therefore，the strength index testing of GFRP is more complex than that of steel. The end anchorage problem of large-diameter full-scale GFRP test specimen is solved by laboratory test. Through the tensile test of full-scale specimen of large-diameter GFRP in the tensile testing machine，the variation laws of the basic mechanical properties of large-diameter glass fiber bar，such as tensile strength，tensile elastic modulus and elongation ratio，are studied under different loading rates. In addition，the failure mechanisms between the GFRP bar and steel bar are compared. The experimental results demonstrate that，with increase of loading rate，the tensile strength and elongation ratio of GFRP bar increase significantly，while the elastic modulus remains roughly constant；the mechanical characteristics and failure modes are determined by the materials? composition and structure.

The high-alkaline pore fluid may affect buffer and sealing properties of bentonite during a long-term period in the geological radioactive waste repository. In order to investigate the dissolution and its mechanism of bentonite by hyper-alkaline pore water，the permeability and erosion tests，in which NaOH solutions is used to simulate the hyper-alkaline pore water，are carried out for the compacted Gaomiaozi bentonite samples with an initial dry density of 1.70 g/cm3；then X-ray diffraction(XRD) and energy dispersive spectrometer(EDS) are applied to investigate the alteration of mineral components and Mg content of samples. Test results present that：(1) Montmorillonite，quartz，albite and microcline(or cristobalite) are components of Gaomiaozi bentonite；and montmorillonite is the main effective component. (2) No original minerals vanish and secondary minerals produce are observed during the experiments simulating period，but values of montmorillonite and Mg content of bentonite samples decrease with the increase of concentration of the hyper-alkaline solution，which indicates the dissolution of montmorillonite under the erosion of the hyper-alkaline solutions. Therefore，under long-term infiltration of hyper-alkaline pore water，bentonite dissolves，which results in the reduce of the swelling potential，amplification of the effective porosity and permeability，and finally the buffer and sealing capability of bentonite dropping.

In order to realize visual analysis and prediction of slope stability，a worksite slope in Shuangbai，Chuxiong is investigated. Based on digital elevation model(DEM)，combining the factors such as rainfall，topography and geomorphology，and soil characteristics，the threshold rainfall for deformation and instability of the slope unit is calculated by the rainfall threshold model. And the effects of rainfall infiltration and gradient on slope stability are analyzed. Comparing the results between the model prediction and the actual monitoring of slope stability，it is shown that the rainfall threshold model can simulate well the needful rainfall which can induce the instability of slope in each unit. The unit of slope may be instable when the rainfall is larger than the rainfall threshold of slope. The simulation result fits the real slope instability cases very well.

According to the theoretical analysis combining with the numerical simulation method，the effect of microparameters on macroproperties of parallel bonded model is investigated systematically. Firstly，the theoretical formulas between microparameters and macroproperties are proposed qualitatively；then，the quantitative relationships are put forward by PFC2D software. The research result shows that：(1) The Young?s modulus of the calculation model is mainly determined by the contact Young?s modulus of particles and bonded Young?s modulus of particles；and they are in a linear relationship with the Young?s modulus all. What?s more，The Young?s modulus is affected by contact stiffness ratio of particles，bound stiffness ratio of particles and particle size；and the three ones are logarithmic relationship with the Young?s modulus all. (2) The Poisson?s ratio is mainly determined by stiffness ratio of particles and they are in a linear relationship. Simultaneously，it is slightly affected by particle size. (3) The compressive strength is mainly determined by bound stress ratio of particles ?b，m/?b，m；and it is slightly affected by friction factor ?. When 0＜?b，m/?b，m＜2，the compressive strength is mainly influenced by bound tangent stress?b，m；when ?b，m/?b，m≥2，it is mainly influenced by bound normal stress ?b，m. Then the correlative relations with certain referential significance are given；and the reliability of correlative relations is proved by case study. The study has directive meaning to quickly and reasonably determine the microparameters of PFC model.

The anti-sliding characteristics of single double-row and composite anti-slide micropiles are studied through three model experiments. The monitoring results of slope displacement indicate that：(1) micropiles can provide relatively bigger sliding resistance and decrease deformation rates；and it has obvious slope reinforcement effect. (2) Comparing with single double-row micropiles，composite micropiles have better reinforcement effect and the sliding resistance increases by 6.8%. There are three failure models namely bending failure of the pile body，disengaging between pile and soil and the fracture failure of piles. The crack angle of single double-row piles，with bending-tensile failure，is bigger value of 65.7°，while the value of composite piles is 33.9°， with bending-shearing failure. And the backward piles? cracks are more obvious than the forward piles. The soil pressure acting on the free section of single double-row pile body is “S” shaped distribution. The backward piles bear bigger soil pressure owing to directly contacting loads；meanwhile，the ratios of the maximum of soil pressure between the forward piles and backward piles are 0.53∶1–0.50∶1. As a result of the empty area between the pile and soil，the maximum of soil pressure distributes in 10% of the length of the pile above the sliding surface. The sliding resistance below sliding surface is inverted with triangular distribution under small pushing force and presents rectangular distribution under big pushing force. Due to the effect of coupling beam，the positive bending moment produced at the top of the forward piles is bigger；and the maximum negative moment appears around the sliding surface. The ratio of maximum negative bending moments between the backward piles and the forward piles is 0.67∶1–0.80∶1.

Aiming to composite foundation with rammed cement-soil piles in soft ground，the contrast tests for a group of composite foundation with 9 rammed cylindrical cement-soil piles and three groups of composite foundation with 9 rammed tapered cement-soil piles are performed in laboratory，respectively. The relationships of average settlement-load and average pile-soil stress ratio-load，and the load transferring law of four groups of composite foundations with rammed cement-soil piles under the same condition are studied. The test results indicate that：(1) The differential settlement between pile and soil can be adjusted by rammed tapered cement-soil pile；and the ground settlement can be decreased and its bearing capacity can be enhanced obviously. (2) The bearing behaviour of rammed tapered cement-soil piles in the composite foundation can be exerted by enhancing its taper. The average pile-soil stress ratio of composite foundation with rammed tapered cement-soil piles is higher than that of composite foundation with rammed cylindrical cement-soil piles. (3) With the increase of the taper， the decay rate of axial force in rammed cement-soil tapered pile is increased and the load transferring depth is reduced. The bearing characteristic of rammed tapered cement-soil pile is better than that of rammed cylindrical cement-soil pile. The taper is bigger，the pile properties can be exerted more fully.