Expanded polystyrene (EPS) geofoam has been increasingly used in geotechnical engineering applications to replace conventional backfill material or to reduce earth pressure on retaining and buried structures. In most of these applications, geofoam blocks are installed in direct contact with different construction material (soil, concrete, steel, wood, etc.). This results in a composite system that is subjected to loading in both the normal and shear directions. Therefore, successful analysis and design of these composite structures require a detailed knowledge of interface strength characteristics of geofoam under a combination of normal and shear stresses. In the current research, an attempt has been made to study the interface shear characteristics of geofoam with selected materials, including concrete, wood and steel. Three different geofoam densities namely, 15, 22 and 39 kg/m³ were used in this study. A series of direct shear tests (DST) was conducted with a shear box of dimension 100 mm × 100 mm × 50 mm under three different normal stresses 18, 36 and 54 kPa. Test results revealed that geofoam density and applied normal stress have significant effects on the vertical compression and interface strength properties (i.e. adhesion and friction angle) of the investigated geosystem. Surface roughness was found to play a significant role in the shear resistance at the contact. Geofoam–concrete interface showed maximum strength as compared to wood and steel materials. Care should be exercised when placing geofoam against steel or wood surfaces as the mobilized friction angle is generally small and sliding may develop depending on the applied normal stress level.

中文翻译：

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论泡沫塑料密度对复合地球系统界面剪切行为的影响

膨化聚苯乙烯（EPS）土工泡沫已越来越多地用于岩土工程应用中，以代替传统的回填材料或降低土方和固定结构的土压力。在大多数这些应用中，安装的泡沫块与不同的建筑材料（土壤，混凝土，钢材，木材等）直接接触。这导致复合系统在法向和剪切方向上都承受载荷。因此，对这些复合结构的成功分析和设计需要详细了解在正应力和剪应力共同作用下的土工泡沫界面强度特性。在当前的研究中，已经尝试研究选定材料（包括混凝土，木材和钢）的泡沫土的界面剪切特性。本研究中使用了³个。使用尺寸为100 mm×100 mm×50 mm的剪切盒在三种不同的法向应力18、36和54 kPa下进行了一系列直接剪切测试（DST）。测试结果表明，土工泡沫的密度和所施加的法向应力对所研究的地球系统的垂直压缩和界面强度特性（即粘附力和摩擦角）有显着影响。发现表面粗糙度在接触处的抗剪切性中起重要作用。与木材和钢材相比，土工泡沫-混凝土界面显示出最大的强度。将泡沫塑料抵靠在钢或木材表面上时应格外小心，因为动摩擦角通常较小，并且根据所施加的法向应力水平可能会产生滑动。