1. Introduction
At present in our country, reinforced retaining wall using geotextile material (reinforced soil retaining wall Geosynthetic-) is used in many different fields in building construction as assigned common in urban areas, reinforcing soft soil ... With steep roof structure, high economic efficiency, aesthetic value especially high shock resistance it is indeed appropriate solutions replace old retaining wall structures Dictionary in the formulation, particularly in urban aesthetic requirements and building area is limited. Danang too, is a tourist center of the country, with many areas resot, coastal urban areas are built around Son Tra peninsula, the reinforced retaining wall solution is the choice of many investors , the design consultant to replace the classic wall.
With a solution designed with reinforced walls in slope stabilization works at Mecure Son Tra, the authors wanted to give a lesson glasses Working experience in design, slope stability calculations reinforced retaining wall that uses geotechnical materials to help software engineers GEOSLOPE, Plaxis, Excel in Vietnam conditions no rules of construction design reinforced walls.
2. Theoretical Foundations slope stability calculations
2.1 Theory slope stability calculations according Slope and Plaxis [1] [5] [6] [8]
Software Slope / W 2004 balance of theory of human limits and torque to calculate safety factor against deep sliding. Safety factor (Factor of Safety, FS, Equation 2.1) is defined as the ratio of torque with torque sliding skid (Abramson et al. 2002). Limit equilibrium theory (Limit Equilibrium Theory) is applied to determine the safety factor assuming cylindrical sliding surface.
(2.1) Bishop method is used to determine the coefficient of stability, FS. Bishop method based on classical fragmentation method takes into account interactions between the pieces (Das 2006) and stability coefficient, FS, is defined by the equation (2.2) (2.2) where: c - cohesion , - friction angle, w - the weight of each piece, b - length of each piece along the slip, u - Pore pressure, - angle of each piece,. FS coefficient is determined according to (2.2) to ensure greater than or equal to 2.3 to achieve the design requirements) stability factor determined by the finite element method is defined based on the relationship of stress at a point , is the ratio of the shear strength of soil, f, and shear stress, , the load caused by the earth at a point (Equation 2.3) (2.3) or (2.4) Where:,. PLAXIS software determining factor FS by iterative trial and error with change FS to achieve balance in the equation (2.4) when the stress caused by the load at one point to be determined (Brinkgreve et al. 2006) . In this method parameters and c tan be shortened by the formula (2.5): (2.5) where: c and intensity parameters is true; cr and r the intensity attenuation parameters. Compact process is controlled by parameters. This parameter increases gradually until the collapse occurs. The safety factor is worth the time of the destruction. 2.2 Theory MSE wall calculated under accounting norms England and America [3] [7] The order prescribed for the calculation of the UK (BS8006-1995) and the US (FHWA- NHI-00-043) are summarized in the following order: Step 1: Identify the basic data originally designed: 1. Choose the design process: NHI-00-043 BS8006-1995 or FHWA-. 2. Determine wall height, H; Preliminary net length, L (L 0.7H, L 3m) 2. Select the distance between the core layer, Sv. 3. Soil density reinforced, r; friction angle, r; cohesion, cr. 4. Soil bulk density after wall, d; friction angle, d; cohesion, cd. 5. Ground soil density, f; friction angle, f; cohesion, cf. 6. Determining the load on top of the wall, q. 7. Calculate the required core length. Step 2: Calculate the volume stable soil aggregates: 1. Check aggregate not lag anchors. 2. Check if not broken remains. Step 3: Check the overall stability: 1. Check flip. 2. Check the horizontal slide. 3. Check the bearing capacity of the ground. 4. Check slide overall stability. With each height calculations H at position 3 cross. The author has set up a spreadsheet with Excel (Shown in the Appendix). With regard to the overall stability test is performed by software and Flaxis Geoslop. 3. Computing applications projects Mecures Son Tra [4] 3.1. Project Introduction Project MERCURE RESORT Son Tra Resort was built in Bai Trem ear, Son Tra. Investor of the project is the company JSC Saigon General Service (SAVICO). The project has a total area of 5.7 hectares, including a 4-star hotel of 120 rooms and 22 luxury villas, with a total investment cost of USD 20 million. Figure 3.1. Perspective of projects Mecure Son Tra 3.2. Solution structure reinforced retaining wall Arrangement reinforced retaining walls category in three locations before parking, tennic yard, before the hotel with two types of wall and bending mainly bundle block (Figure 3.2, 3.3) . Figure 3.2. Typical cross section front wall hotel segment Figure 3.3. Cross section detail brick wall Block causeway sections H1 = 3m geotechnical Grid 1 axis using 2 types: 5 layers under use class 4, 4 next class using Class 1, the distance between the mesh layer is 0.4m. Parties in part reinforced by soil grid covered the advantage with K≥0.95. Using Geocell 10cm bottom, pouring rubble inside and compacted at K≥ coefficient 0.95, the bottom lining of non-woven geotextile TS20. Behind the wall surface layer of macadam drainage 0.3m thick , is separated from the soil inside with layers of non-woven geotextile TS20. The surface of the wall using KT Block (20x20x40) cm and placed on a reinforced concrete foundation beam f'c = 25Mpa, KT (60x45 ) cm. 4. Results and discussion The calculations in section 3 positions are shown in the spreadsheet in Appendix paper and with three cross author has used software to calculate GEOSLOPE and Plaxis safety factor FS at positions corresponding sectional results presented in Table 4.1 Table 4.1. FS factor of three sections corresponding software GEOSLOPE and Plaxis Location FS (Kmin) MCN Parking 1,659 1,588 MCN Tennis 1987 1992 hotel MCN 1,815 1,698 In 22 BC 171- 1987 standards, the coefficient ratios Full FS allows the [FS] = 1.3. Based on the results of the analysis were then cross all three positions are ensuring stability. The coefficient stability of the software FS GEOSLOPE and Plaxis calculations similar, minor deviations. Plaxis software is based on theory balance should limit high accuracy but requires complex data input and correct blessing, while too large shear deformation compatible leads to distortion violated. With funding conditions, survey equipment limited experiment in our country today, the software Plaxis not apply. With GEOSLOPE / W is the simple software, require fewer inputs and are widely used, but its accuracy and convergence depends on the subjectivity of modeling, is the classic method of calculation, not interested applicants and deformation capacity. 4. Conclusion Solution reinforced retaining wall using geotextile materials well suited to the conditions of Son Tra Peninsula by aesthetic and economical because the packing material Courts will be in place should be able to get to widely used in this area. When calculating reinforced retaining wall design checks MSE overall stability depends critically on design experience placements especially blessed magazine sections as sections in position Previous hotel with many different wall height (Figure 3.2). The designer must check the overall stability with many dangerous slip in many different locations to locate the most dangerous sliding surface to check the stability of the building. Calculation results show that, at the previous location hotel sectional author has used three different slip to test the overall stability in the location section. This result fully simulate and predict accurately the slip danger
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