含水率和顆粒級(jí)配對(duì)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(guān)注，但對(duì)大粒徑、粉質(zhì)粘土填充、稍密狀態(tài)下碎石土的力學(xué)性能涉足較少。根據(jù)該類型碎石土特點(diǎn)及大量勘察結(jié)果配置出兩種比較典型級(jí)配的稍密碎石土，通過(guò)大型直剪試驗(yàn)儀測(cè)定了不同含水率狀態(tài)下碎石土試樣的抗剪強(qiáng)度，繪制剪應(yīng)力與水平位移的關(guān)系圖，通過(guò)一元回歸得出稍密碎石的抗剪強(qiáng)度指標(biāo)c、φ值，分析了不同含水率、不同級(jí)配對(duì)稍密碎石土抗剪性能的影響。結(jié)果表明：隨著含水率的增大，碎石土粘聚力總體呈減小趨勢(shì)，但變化趨勢(shì)具有顯著的階段性且和粉質(zhì)粘土的含量有關(guān)，含水率變化對(duì)碎石土內(nèi)摩擦角的影響較小。用規(guī)范推薦方法計(jì)算了該類型碎石土地基承載力，并與地方規(guī)范經(jīng)驗(yàn)取值和勘察工程實(shí)踐取值進(jìn)行了對(duì)比，結(jié)果表明：含水率對(duì)地基承載力影響較大，且與碎石土填充物的粉質(zhì)粘土含量有關(guān)，粉質(zhì)粘土含量越高，承載力影響越大。

關(guān)鍵詞：粉質(zhì)粘土碎石；含水率；抗剪強(qiáng)度；地基承載力

中圖分類號(hào)：TU472.1文獻(xiàn)標(biāo)志碼：A文章編號(hào)：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(guò)總質(zhì)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(qiáng)度的力學(xué)參數(shù)有關(guān)。碎石土邊坡的剪切破壞，與滑坡巖土體的抗剪強(qiáng)度直接相關(guān)[3]。因此，科學(xué)地開(kāi)展土力學(xué)試驗(yàn)，準(zhǔn)確地獲取碎石土的抗剪強(qiáng)度指標(biāo)，客觀、全面地認(rèn)識(shí)碎石土的抗剪性能，是解決工程中碎石土強(qiáng)度問(wèn)題的基礎(chǔ)，對(duì)碎石土地基承載力分析和碎石土邊坡穩(wěn)定性整治具有十分重要的作用[45]。……