A project of reinforcement embankment for earthquake

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					                A PROJECT OF REINFORCEMENT EMBANKMENT
                       FOR EARTHQUAKE RESISTANCE
                   OF THE MURAYAMA-SHIMO RESERVOIR,
                         AN EXISTING EARTH DAM

                                                                                                                                        Bureau of Waterworks
                                                                                                                                    Tokyo Metropolitan Government




1. INTRODUCTION
                                                                                                                                                                                             Fs=2.09                        Fs=1.17
We report that an example of an earthquake proofing measures on the Murayama-Shimo                                                                               Fs=1.84        Fs=1.78
                                                                                                                                                                                                                                                     Fs=1.17
Reservoir, an existing earth dam.                                                                                                                                                                                                                                   Fs=1.07

1.1 Outline of The Murayama-Shimo Reservoir
Reservoir
  Location : The northwest part of Tokyo
  Construction : Between 1916 and 1927
  Total storage capacity :     12,148,000m3                                                                                                                                       Fig.4. Results of the Sliding Stability in the Case
  Effective storage capacity : 11,843,000m3                                                                                                                                              of South-Kanto Epicentral Earthquake
  Surface area at full-filed water : 1.1km2
                                                                                                                                                                                                                   32.0cm
Embankment
                                                                                                                                                                                                    94.5cm
 Structure : zoned earth dam                                                                                                                                                                                                                           0.9cm
 Top lengths :      587.27m
 Height :              32.6m
                                                                                       Photo.1. The Murayama-Shimo Reservoir

                                                                            8.0
                                                 Concrete slab
                                                                                  Bomb shield
                                                                                           1:2                                                                            Fig.5. Prediction of the Volume of Residual Deformation
                                                1:3.0                Core                     .0     counter weight fill
                                                        Shell                         Shell
                                                                                                                                                                                in the Case of South-Kanto Eepicentral Erthquake

                                                                                  Cut-off wall of water

                                           Fig.1. Cross Section of Existing Dam Body                                                               3. REINFORCEMENT SLOPE WITH GEO-TEXTILE
                                                                                                                                                   In case of normal time after completion, the sliding safety factor did not satisfy f =1.2 of
2. DESIGN OF REINFORCEMENT EMBANKMENT                                                                                                              the aim, then reinforcement is necessary.
In January 1995, a gigantic earthquake M7.3 attacked Kobe-city. Soon we performed                                                                  We decided to perform reinforcement with the geo-textile.
a seismic diagnosis for this earth dam. This diagnosis cleared that the embankment
would have damage at the time of an earthquake M7.0 class.                                                                                         3.1 The Friction Characteristics of Geo-Textiles and Filling Materials
                                                                                                                                                   We use pulling test for setting the friction characteristics of geo-textiles and filling
2.1 Choice of the Earthquake to Examine                                                                                                            materials.
  Level 1 earthquake motion (That occurred once to twice in occupied term)
          The occurrence probability 1/30 years, M7 class                                                                                                                                                                                                                                Lateral displacement
  Level 2 earthquake motion ( The occurrence probability is very low)                                                                                                                                                                                       Air                          transducer
                                                                                                                                                                                                                                    Air bag
                                                                                                                                                                                                                                                                                   Geogrid
          The occurrence probability 1/300 years, M8 class
                                                                                                                                                                                                                                      100       Backfill soil
                                                                                                                                                                                                                                      100
        Table.1. The Assumed Input Earthquake Motions                                                                                                                                                                                 100       Backfill soil
                                                                                                                                                                                                                                      100
            Level of Occurrence Assumption                                                       Acc Max Speed Max
                                                                            Type       Magnitude
           Earthquake Probability Earthquake                                                       (gal)   (kine)                                                                                                                                                                          Load cell to measure
                                                                                                                                                                                                                                 W: 400




            Level 1                1/30 years                                                                                                                                                                                                                                              the pull-out load
                                                   Ansei-Edo              Inland              6.9         186.3           11.1
                                                                                                                                                                                                                                             L: 1000
                                                  South-Kanto
                                   1/300 years                 Trench                         7.9         333.4          126.4
                                                    epicentral
            Level 2
                                                   Tachikawa Neighbor
                                       -                                                      7.1         458.2          147.1
                                                   dislocation Inland
                                                                                                                                                          Photo.2. Pulling Testing Machine                                       Fig.6. Mechanism of Pulling Testing
                             600
                             400
                                                                                                                                                   3.2 Placement of Geo-Textile for Reinforcement Slop
                Acc.(gal)




                             200
                               0
                            -200
                                                                                                                                                     The geo-textile is laid at the intervals of 1.6m in height for an anti-sliding failure
                            -400                                                           South-Kanto epicentral earthquake
                                                                                                              南関東地震                                  measures as a main.
                            -600
                                   0       5            10           15         20            25       30         35           40                    The geo-textile is laid at the intervals of 0.4m in height for preventing surface
                                                                             Time(sec.)
                                                                                                                                                     landslide as an assistance.
                                       Fig.2. Example of the Earthquake Wave Pattern,
                                              South-Kanto Epicentral Earthquake
                                                                                                                                                                                        TP.90.000
                                                                                                                                                                                                                                                        4@400 400



                                                                                                                                                                                                                                                                                   500




                                                                                                                                                                                                       TP.89.500
2.2 Design of Reinforcement Dam Body                                                                                                                                                                         TP.87.900
                                                                                                                                                                                                                                                        =1600
                                                                                                                                                                                                                                                                    7@1600=11200




Design                                                                                                                                                                                                           TP.86.300
  At first, designing a sectional structure by use a seismic coefficient method.                                                                               The main reinforcement material                    1:1.0
                                                                                                                                                                                                                                                                                            10000




                                                                                                                                                                    TA>=21.6kN/m,L=6.8m                              TP.84.700
  Then, confirming the earthquake proofing performance and the stability of the slope by                                                                                                                                 TP.83.100
                                                                                                                                                                                                                                                                                                    17000




                                                                                                                                                                        The main reinforcement material
  use a dynamic analysis and a slope stability analysis.                                                                                                                     TA>=30.0kN/m,L=6.8m
                                                                                                                                                                                                                              TP.81.500
                                                                                                                                                                                                                                             Top of backfill TP.80.000
                                                                                                                                                                                                                                          TP.79.900
                                                                                                                                                                                                                                                             1600




                                                                                                                                                                               The main reinforcement material
Reinforcing structure                                                                                                                                                               TA>=36.0kN/m,L=6.8m                                     TP.78.300

 To be reinforced with filling on the downstream side.
                                                                                                                                                                                                                                                                                   3400
                                                                                                                                                                                                                                                                                           7000




                                                                                                                                                                                                 The assistance reinforcement material               Backfill
                                                                                                                                                                                                          TA>=2.0kN/m,L=2.0m        TP.74.900
 To install an inclined drain and a horizontal drain on the downstream side.
                                                                                                                                                                                                                                                                                    1900




                                                                                                                                                                                                          Level drain
 To be constructed in an acute angle of 45 degrees.                                                                                                                                                                                               TP.73.000
                                                                                                                                                                                                                    Foundation forming

                                                                                     Cement-stabilized soil
                                                                          10.0m               Counter-weight fill                                                                      Fig.7. A Placement Example of Geo-Textile
                                               Concrete blocks       .5              1:2
                                                                 1:1                    .6             Geo-textile
                                                                                               15.0m
                                            1:3.0            Shell
                                                                     Core
                                                                                     Shell                   1:1.0
                                                                                                                                                   4. CONCLUSION
                                                                                    drainage                                                         We have ensured a sufficiently high seismic stability of an existing earth dam.
                                                                                                    Existing dam body
                                                                                                                                                     This project is the first case of reinforcing an existing earth dam by means of geo-
                                       Fig.3. Cross Section of Designed Dam Body                                                                     textile reinforcement.