| Author | Panich Voottipruex |
| Call Number | AIT Diss. no. GE-99-01 |
| Subject(s) | Embankments
|
| Note | A dissertation submitted in partial fulfillment the requirements for the degree of
Doctor of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. GE-99-01 |
| Abstract | A fully instrumented test wall/embankment reinforced with hexagonal wire was
constructed on soft Bangkok clay foundation in Thailand. The reinforced
wall/embankment consists of l 0 degree inclined gab ion facing with hexagonal wire mesh
reinforcements on one side and sloping unreinforced sandfill in the opposite side with a
total height of 6.0 meters. Strain gages were affixed to the wire mesh to monitor the
tension stresses. High strength wires were also used to measure the displacement in the
hexagonal wire reinforcement. The lateral earth pressure coefficient, K, measured during
the wall construction varies from a value corresponding to the active condition, Ka, at the
base of the wall, to a value nearly at at-rest condition, K0 , at the top of the wall with KII<a
equal to 1.6 which is between geogrids and metal strip s. The maximum tension line
interpreted from the observations of the strains induced in the hexagonal wire mesh
reinforcement appeared to be in between the tie-back wedge or the Coulomb/Rankine
failure plane and the coherent gravity failure plane. The maximum displacement
measured from high strength wire extensometer agreed well with maximum lateral
movement measured by the inclinometer. The maximum ground surface settlement of
450 mm was observed at the front face of embankment at 630 days from beginning of
construction. The degree of consolidation of subsoil foundation during the same period is
80 % by using Cv from Asaoka' method. The lateral movement in the subsoil is about 35
mm at the weakest zone of about 2.5 m to. 4.00 m depth below the general ground
surface. The excess pore pressure observed below the embankment at 3 m and 6 m depths
indicate build up at first and gradually dissipated during soft clay consolidation. A
relationship was obtained between the displacements and tensions induced in hexagonal
wire mesh. All measurements showed the zinc-coated hexagonal wire mesh (core
diameter = 3.0 mm) displayed higher tensions induced in the wire than the PVC-coated
hexagonal wire mesh (core diameter = 2.8 mm).
From the pullout test results, the maximum pullout load from the laboratory tests
yielded higher value than that from the field pullout tests because the laboratory pullout
tests has smaller scale when compared to the field pullout tests. Moreover, the faci ng
conditions are not similar, and so are the boundary conditions. Furthermore, the
compaction and moisture contents in the laboratory can be controlled better than that in
the field. The laboratory pullout tests yielded peak pullout resistances at relatively low
displacements of the wire mesh. On the other hand, the fi eld pullout tests generally
yielded peak pullout resistances at relatively larger displacements. The general empirical
equations for both laboratory and field pullout test which can be used for estimating the
maximum pullout load at failure in the design of embankment reinforced with hexagonal
wire mesh in si lty sand backfill are proposed.
The interaction behavior between hexagonal wire mesh and silty sand backfill can
be evaluated from pullout tests. The pullout resistance of the hexagonal wire mesh
reinforcement consists of two components, namely: friction resistance and passive
bearing resistance. The friction resistance/displacement relationship of a hexagonal wire
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mesh can be simulated by a linear elastic-perfectly plastic model. The passive bearing
resistance of an individual bearing member can be modelled by a hyperbolic model The
zinc-coated wire mesh has total pullout resistance higher than the PVC-coated wire mesh
in both silty sand and weathered Bangkok clay backfill. In silty sand backfill, the bearing
resistance is 79% and 75% of total pullout resistance for zinc-coated and PVC-coated
hexagonal wire mesh, respectively. Moreover, the friction resistance is 21 % and 25% of
total pullout resistance for zinc-coated and PVC-coated hexagonal wire mesh,
respectively. In contrast, for weathered Bangkok clay, the bearing resistance is 75% and
70% of total pullout resistance for zinc-coated and PVC-coated hexagonal wire mesh,
respectively. In addition, the friction resistance is 25% and 30% of total pullout resistance
for zinc-coated and PVC-coated hexagonal wire mesh, respectively. A new proposed
analytical method is utilized for predicting the pullout bearing resistance. Its validity is
confirmed by the reasonable agreement between the calculated and actual bearing
resistance from laboratory pullout test results.
The numerical simulation based on finite element analysis were performed to
simulate the behavior of the hexagonal wire mesh embankment on soft ground foundation
The lateral displacements of the wall face from finite element agreed reasonably with the
measured field data. From the overall point of view, the calculated values using
permeability equal to 2 times the laboratory test value agreed with field data. The
calculated maximum excess pore pressures using the permeability value of 2 times the
laboratory test value also agreed with the measured data. The comparison of the
settlement of hexagonal wire mesh reinforced embankment without and with weathered
crust underneath the embankment from finite element analysis revealed that the
settlement of the embankment in the former is approximately two times more than the
latter. From the FEM analysis, the direct shear mechanism is found to be the appropriate
model for simulating the interface behavior of the embankment/wall reinforced with
hexagonal wire mesh with silty sand backfill at stress levels during service conditions on
soft ground. |
| Year | 2000 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. GE-99-01 |
| Type | Dissertation |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical and Earth Resources Engineering (GE)/Former name = Geotechnical Engineering |
| Chairperson(s) | Bergado, Dennes T.; |
| Examination Committee(s) | Balasubramaniam, A.S.;Otsu, Hiroyasu;Pichai Nimityongsakul;Miura, Norihiko; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2000 |
