Applied Mechanics and Materials Vols. 744-746

Abstract: The soft ground including the mud, muddy clay, silty clay etc. is widely distributed in the coastal areas of China. Due to the poor permeability and low bearing capacity, ground improvement is usually necessary before construction. Owe to the low cost and high efficiency, the drainage consolidation methods including surcharge preloading and vacuum preloading methods are the most popular method for the improvement of the soft ground. The consolidation theories are introduced according to the time sequence and the emphasis is put on the radial consolidation theories considering the smear effect and the well resistance.

Abstract: Water content has a great influence on the rock mechanics properties. Four kinds of rock samples have been tested in the MTS Electro hydraulic Tri-axial Servo Test System. The result shows that with the increase of water content, the rock uniaxial compressive strength and elastic modulus value are declining. We get the fitting equation between water content and rock mechanical properties with four kind of rocks, provide a new basis for slope stability analysis and landslide prevention and control measures.

Abstract: Based on a shear test for jointed rock sample conducted by former study, a numerical improved method DDARF is carried out to simulate the shear test. The simulation result of shear fracture phenomenon show high compatibility with the model test. Different fracture phenomenon and peak strength value of shear testing are explored in the condition of different colinnear and ladder echelon arrangement of cracks.

Abstract: In order to improve the bearing behavior and the bearing capacity of single pipe pile, the technology of step cross-section pipe-pile is proposed.Based on FLAC3D, the finite difference model of the pile-soil interaction established,bearing behaviors of step cross-section pipe pile and unimate cross-section pipe pile is studied comparatively and bearing performance influence factors of step cross-section pipe pile is discussed.The results show that the bearing capacity of step cross-section pipe pile is much higher than unimate cross-section pipe pile in the same geological conditions and material dosage. For layered foundation, the bearing capacity of single pile may be improved by setting variable cross-section pile joint in relatively hard soil. But the depth of joint embedded in hard soil has little influence on bearing capacity of single pile.There is an obvious effect on increasing capacity of single pile by improving soil properties of soft soil surrounding pile.

Abstract: Damp Newton algorithm based on FEPG system is developed for calculating strain softening problem. The algorithm can solve displacement and yield surface equation simultaneously. Soften modulus is introduced into D-P yield function. The example result shows that, the algorithm with damp factor can be used to solve softening problems. The plastic theory described by finite element weak form has no requirement of continuity, so appropriate outcome can be obtained by first-order element. Descent segment of stress-strain curve and cloud picture of finite shear band are presented.

Abstract: Through detailed investigation to development status of grouting technique, summarizes the classification of geotechnical grouting technology, selection of materials grouting, Finally, by anchoring engineering and tunneling engineering described in detail grouting process，grouting order, grouting parameters and grouting end standard in the geotechnical engineering application，This research has practical guidance and theoretical reference value for similar projects.

Abstract: This paper introduces a design program for supporting of deep foundation pit through the actual example for Beijing Moisten the world Center project to solve the difficulties of high water content in foundation soil, sensitiveness to surroundings, and difficult control of quick sand and flowing mud in the process of supporting of foundation pit. This program adopts a supporting system with upper soil nailing wall and lower pre-stressed anchor pile and a comprehensive water-proof curtain (Retaining piles + Long spiral high pressure jet grouting & mixing piles) to effectively solve the above difficulties. It is indicated through actual monitoring that displacement and settlement of foundation pit meet the specification and design requirements with excellent water-proof effect. The successful application of this program provides a reference for foundation pit engineering with rich underground water, especially for engineering at hard soil layer and stratum with sand and gravel that are apt to the formation of cement-soil grouting and mixing piles, as well as engineering with limitation on dewatering of foundation pit.

Abstract: Reasonable determination of entire layer or sublayer mining method is the key factor of safe and efficient mechanized caving mining of 14.0～28.0m ultra thick seam , numerical simulation on the entire (sub) layer coal caving mining by the FLAC3D , studying the stress and displacement variation of overburden strata , combining the underground pressure theory , comparative analysis on the calculation results . The results show that entire (sub) layer mining roof stress , movement contours are presented in a semi-elliptical arch morphology , indicating the existence of a high arch structure overburden formations , mining process appears roof tensile destruction , but the entire layer caving tensile stress intensity is lower than sublayer caving . When advancing the same distance , entire layer caving puts a greater impact on the overburden strata than the sublayer caving , has some features such as big range of influence and extent , small roof pressure , lead abutment pressure forward from grand , short time of achieving full extraction , etc.

Abstract: By adopting the conventional pile foundation to treat the area of thick overburden on soft soil, the reinforcing effect can’t meet the use requirement: by adopting the bulk material pile, the lower pile body strength can’t be ensured, and by adopting the cemented soil mixing pile for reinforcing, the pile is difficult to form and the reinforcing depth can’t meet the requirement. This paper aims to overcome the defects of the conventional construction method by adopting different materials to treat, namely, the concrete rigid pile is adopted for reinforcing the soft soil layer with poor soil body quality and the cement mortar flexible pile is adopted for reinforcing the overburden with excellent soil body quality, therefore not only the reinforcing effect is ensured, but also the construction cost is saved.

Abstract: Due to the earthquake of Yushu in April 14, 2010, Airport Road landslide No.3 deformed cracking, resulting in lower stability of slope, triggering landslides and other diseases. Selecting the section 2-2 (mileage K823 + 809) of Airport Road landslide No.3 as the calculation section, we use the ABAQUS finite element program to establish landslide numerical mode. The slip mass of landslide was simulated by the elastic-plastic damage constitutive model, and the bedrock was analyzed as Mohr - Coulomb constitutive model. Landslide No3 is analyzed for example, and showed that earthquake triggering mechanism elastplastic damage constitutive model can describe the landslide very well.