Shivashankar, Ramaiah creator Bergado, Dennes T. Chairperson Noppadol Phien-Wej Co-Chairperson Balasubramaniam, A.S. Examination Committee Karasudhi, Pisidhi Examination Committee Honjo, Yusuke Examination Committee Holtz, Robert D. Examination Committee Bell, J. Richard Examination Committee The Government of Japan Scholarship Donor text series technical report th Bangkok Asian Institute of Technology 1991 continuing eng 443 p. The general objectives of this research were as follows: ( 1 ) To study the interaction mechanisms and the factors affecting the pullout resistances, as well as to develop prediction equations for the pullout resistances of welded-wire reinforcements with low-quality, cohesive-frictional backfill materials. ( 2 ) To study and evaluate the performance of a welded-wire mechanically stabilized earth (MSE) wall and embankment system which utilized locally available, low quality soils as backfill materials on soft ground conditions. ( 3 ) Comparison of the laboratory pullout resistances with the predicted pullout resistances using the finite element program REA at the end of 1 in. (25.4 mm) pull; and the analysis of the MSE wall/embankment system to predict its behavior immediately after construction, also by using the finite element program REA. A total of 544 pullout tests in 253 set-ups were conducted in the laboratory using three different locally available, poor quality, and cohesive-frictional backfill soils comprising of clayey sand, lateritic soil and weathered clay. Prediction equations and design curves for the total pullout resistances in terms of both the soil and the mat parameters were developed from the pullout test data, by a multiple regression procedur'2. The laboratory pullout tests with normal stresses up to 13 T/m (130 kPa) proved that even with such poor to marginal quality backfill materials, the pullout resistances increased with the increase in the confining vertical normal stresses. It was also confirmed that with the compacted cohesive-frictional soils on the dry side of optimum, pullout resistances comparable to that of the good quality granular backfill materials can be generated. The parameters (or coefficients) of the prediction equations showed distinct relationships with the compaction moisture contents for all the three backfill soils. The type of bearing capacity failure mechanism in front of the transverse members of the grid reinforcement was found to occur as general bearing failure mechanism with increasing spacing to diameter or (S/D) ratios of the transverse bars; increasing compaction moisture contents; increasing confining normal stresses and increasing displacement of the transverse members through the soil, or in other words, with increasing stiffness of the backfill soils compared to the stiffness of the transverse members. Otherwise, the failure mechanism corresponds to punching shear failure mechanism. Further, it was found that for (S/D) ratios greater than about 50, the degree of interference of the passive resistant zone of one of the transverse members with that of the adjacent transverse members becomes less significant. (iv) Fifteen constant-strain field pullout tests were conducted on dummy reinforcements left in place in the test embankment at different elevations. The two outer sections comprising of clayey sand and weathered clay backfills generally gave higher pullout resistances from the field pullout tests, while the corresponding values for the middle lateritic section were found to be very much lower. These phenomena can be blamed on the arching effects caused by the excessive subsoil movements and due to the presence of the inextensible reinforcements. The laboratory pullout tests generally yielded conservative values. A full scale experimental and an extensively instrumented welded-wire wall and embankment system (AIT MSE Wall/Embankment) of 5.7 m height with one vertical face was constructed on soft Bangkok clay at the A.I.T. campus. The test embankment used three different types of locally available, poor quality backfill soils namely: clayey sand, lateritic soil, and weathered clay, in the three sections along its length, respectively. The soft clay in the subsoil is about 6 m thick overlain by a surficial 2 m thick layer of weathered clay crust and underlain by a layer of stiff clay. The behavior of the AIT wall was monitored both during the construction and in the post-construction phases, and the data were analyzed. It was observed that the large settlements and the lateral movements of the soft clay subsoil influenced very much the variations in the vertical pressures beneath the embankment and the tensile stresses in the reinforcements. The presence of the inextensible steel grid reinforcements and the interconnection at the facing caused arching effects, that affected the behavior of the test embankment. The maximum tension line did not agree well with either the Rankine or the coherent gravity or the logarithmic spiral failure planes. Compaction induced stresses increased the lateral earth pressures considerably and thereby also increased the tensile stresses in the reinforcements. An overall assessment of the wall behavior suggests a significant deviation from that currently established for mechanically stabilized earth walls resting on comparatively good foundation subsoils. The Reinforced Earth Analysis (REA) finite element computer program was used with the concept of equivalent friction coefficient for the grid reinforcements, to predict both the laboratory pullout test results and the wall behavior. The laboratory pullout tests were treated as plane strain problems, similar to that of an externally loaded sheet pile, with the reinforcements being treated as discrete bending elements. The results were also compared with the corresponding values obtained by using another finite element computer program NONLIN 1. The FEM predictions of the pullout resistances were found to lie between the upper and the lower bound envelopes for the pullout resistances of the grid reinforcements, verifying the laboratory pullout results. The FEM predictions of the wall behavior agreed approximately well with the actual observations. ( v) Finally, it can be concluded that the welded wire or steel grids can be effectively used to reinforce poor quality backfill materials on soft clay foundations. The AIT MSE Wall/Embankment showed no signs of instability either during construction or in the post-construction phases and continues to perform satisfactorily after more than two and a half years since its construction. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Engineering and Technology Thesis (Ph.D.) - Asian Institute of Technology, 1991 Embankments Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B17453 http://203.159.5.9/ait-thesis/detail.php?q=B17453 191197 20260817171216.0