Abstract:The centrifugal model tests are performed on four reinforced soil segmental retaining walls under different toe restraint conditions, which are normal toe restraint, smoothing the block-pad interface, smoothing the pad-foundation interface, smoothing the pad-foundation interface and then excavating the foundation soils in the front of the leveling pad. The influences of the toe restraint condition on the internal stability of reinforced segmental wall under working stress are discussed. The test results show that the toe restraint conditions significantly affect the internal stability of reinforced soil segmental walls. For the wall that the block-pad interface is smoothed, the bottom block slides along the block-pad interface, which leads to an obvious increase in the horizontal displacements and reinforcement strains within the middle and lower parts of the wall and a triangular distribution with height of connection loads between reinforcements and facing. For the wall with the pad-foundation interface smoothed, the foundation soils in the front of leveling pad can provide the pad with enough restraint, thus the internal stability of the wall is the same as that under the normal toe restraint. The purpose of smoothing the pad-foundation interface and then excavating the foundation soils in the front of the leveling pad is to simulate the condition that the toe is scoured. In such condition, the pad slides along its interface with the foundation soils, the facing displacements and the reinforcement strains within the middle and bottom parts of the wall increase significantly, and the connection loads in reinforcements are close to the maximum reinforcement loads under the limit state calculated by the AASHTO method, but the wall still remains stable. In the extreme situation where the toe is eroded by scouring, the effect of toe constraint should not be considered in the design of the reinforced soil segmental retaining walls. For the walls under working stress, the reinforcement loads can be calculated using the K-stiffness method with consideration of the toe restraint effects.
[1] BATHURST R J, SIMAC M R.Geosynthetic reinforced segmental retaining wall structures in North America[C]// Proceedings of the Fifth International Conference on Geotextiles, Geomembranes and Related Products. Singapore: Southeast Asia Chapter of the International Geotextile Society (SEAC-IGS), 1994: 1-41. [2] KOERNER R M, SOONG T Y.Geosynthetic reinforced segmental retaining walls[J]. Geotextiles and Geomembranes, 2001, 19(6): 359-386. [3] LESHCHINSKY D, VAHEDIFARD F.Impact of toe resistance in reinforced masonry block walls: Design dilemma[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2012, 138(2): 236-240. [4] BATHURST R J, WALTERS D, VLACHOPOULOS N, et al.Full scale testing of geosynthetic reinforced walls[M]// ZORNBERG J, CHRISTOPHER B R, eds. ASCE Special Publication No. 103, Advances in Transportation and Geoenvironmental Systems using Geosynthetics. Denver: ASCE, 2000: 201-217. [5] LESHCHINSKY D.Discussion on ‘‘The influence of facing stiffness on the performance of two geosynthetic reinforced soil retaining walls’’[J]. Canadian Geotechnical Journal, 2007, 44(12): 1479-1482. [6] CHEN J F, YU Y, BATHURST R J.Influence of leveling pad interface properties on soil reinforcement loads for walls on rigid foundations[C]// Proceedings of GeoShanghai International Conference 2014. Reston, 2014: 481-492. [7] 陈建峰. 基于墙趾真实约束条件的模块式加筋土挡墙数值模拟[J]. 岩土工程学报, 2014, 36(9): 1640-1647. (CHEN Jian-feng.Numerical modeling of reinforced soil segmental walls under real toe restraint conditions[J]. Chinese Journal of Geotechnical Engineering, 2014, 36(9): 1640-1647. (in Chinese)) [8] 陈建峰, 张琬. 采用K-刚度法设计的模块式加筋土挡墙数值模拟[J]. 岩土工程学报, 2017, 39(6): 1004-1011. (CHEN Jian-feng, ZHANG Wan.Numerical modeling of a reinforced soil segmental retaining wall designed with K-stiffness method[J]. Chinese Journal of Geotechnical Engineering, 2017, 39(6): 1004-1011. (in Chinese)) [9] HUANG B, BATHURST R J, HATAMI K.Influence of toe restraint on reinforced soil segmental walls[J]. Canadian Geotechnical Journal, 2010, 47(8): 885-904. [10] TATSUOKA F, TATEYAMA M, KOSEKI J, et al.Geosynthetic-reinforced soil structures for railways in Japan[J]. Transportation Infrastructure Geotechnology, 2014, 1(1): 3-53. [11] GB50209—98 土工合成材料应用技术规范[S]. 1998. (GB50209—98 Technical standard of application of geosynthetics[S]. 1998. (in Chinese)) [12] ALLEN T M, BATHURST R J.Design and performance of 6.3-m-high, block-faced geogrid wall design using K-stiffness method[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2013, 140(2): 04013016. [13] ALLEN T M, BATHURST R J, HOLTZ R D, et al.A new working stress method for prediction of reinforcement loads in geosynthetic walls[J]. Canadian Geotechnical Journal, 2003, 40: 976-994. [14] BATHURST R J, MIYATA Y, KONAMI T, et al.Stability of multi-anchor soil walls after loss of toe support[J]. Géotechnique, 2015, 65(11): 945-951. [15] MIYATA Y, BATHURST R J, MIYATAKE H.Performance of three geogrid-reinforced soil walls before and after foundation failure[J]. Geosynthetics International, 2015, 22(4): 311-326. [16] BATHURST R J, MIYATA Y, NERNHEIM A, et al.Refinement of K-stiffness method for geosynthetic reinforced soil walls[J]. Geosynthetics International, 2008, 15(4): 269-295.