含水率和顆粒級配對稍密碎石土抗剪性能及地基承載力的影響

盧黎+王華飛+胡岱文

摘要：碎石土因特殊的工程特性而被科研人員關注，但對大粒徑、粉質粘土填充、稍密狀態下碎石土的力學性能涉足較少。根據該類型碎石土特點及大量勘察結果配置出兩種比較典型級配的稍密碎石土，通過大型直剪試驗儀測定了不同含水率狀態下碎石土試樣的抗剪強度，繪制剪應力與水平位移的關系圖，通過一元回歸得出稍密碎石的抗剪強度指標c、φ值，分析了不同含水率、不同級配對稍密碎石土抗剪性能的影響。結果表明：隨著含水率的增大，碎石土粘聚力總體呈減小趨勢，但變化趨勢具有顯著的階段性且和粉質粘土的含量有關，含水率變化對碎石土內摩擦角的影響較小。用規范推薦方法計算了該類型碎石土地基承載力，并與地方規范經驗取值和勘察工程實踐取值進行了對比，結果表明：含水率對地基承載力影響較大，且與碎石土填充物的粉質粘土含量有關，粉質粘土含量越高，承載力影響越大。

關鍵詞：粉質粘土碎石；含水率；抗剪強度；地基承載力

中圖分類號：TU472.1文獻標志碼：A文章編號：16744764（2017）03013807

Abstract：Because of the special engineering characteristics of the gravel soil， it causes more and more attention. However， there are less research about the mechanical properties of the crushed stone soil with large particle size， silty clay and slightly dense state. According to the characteristics of this type of gravel soil and the results of statistical survey， two typical gradation of slightly dense gravel soil are determined. The shear strength of gravel soil specimen under different moisture content is measured by large direct shear apparatus， and the relationship diagram of the shear force and the horizontal displacement under different water cut rate is drawn. The shear strength indexes c，φ value are determined by univariate regression and the impact of moisture content and gradation on the shear strength is analyzed. The results show that with the increase of water content， the cohesive strength of the gravel soil is decreasing， but the change trend is significant and related to the content of cohesive soil. The change of water content has little influence on the friction angle of the gravel soil. Using the specification method to calculate the bearing capacity of foundation， and comparing with the experience value ， the results show that the influence on the moisture content of foundation bearing capacity， and is associated with the silty clay content of gravel soil filling.

Keywords：silty clay gravel； water content； shear strength； foundation bearing capacity

碎石土是指粒徑大于2 mm 的顆粒含量超過總質量50%的土，在自然界分布十分廣泛[12]。碎石土的地基承載力與碎石土體抗剪強度的力學參數有關。碎石土邊坡的剪切破壞，與滑坡巖土體的抗剪強度直接相關[3]。因此，科學地開展土力學試驗，準確地獲取碎石土的抗剪強度指標，客觀、全面地認識碎石土的抗剪性能，是解決工程中碎石土強度問題的基礎，對碎石土地基承載力分析和碎石土邊坡穩定性整治具有十分重要的作用[45]?！?br>