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球形模板压入仪(球模仪)在前苏联和俄罗斯等冻土区土力学性质测试中得到广泛应用。在60多年的工程实践中,试验理论、方法等方面都得到了完善。因其试验简单易行且测试结果能较好地反映冻结土的力学性质,特别是在冻结土黏聚力的长期强度评价及预测方面广泛应用。简要介绍该试验理论、试验方法、试验仪器。以莫斯科郊外冰碛粉质黏土作为研究对象。在恒定-7～20℃温度条件下,在封闭状态下分别进行3、6、20、40次冻融循环试验。对各试验阶段土样进行物理性质测试,之后用球模仪对冻结土样进行强度测试。冻融循环后土样的各物理指标均有不同程度的减小,随着冻融次数的增加,其强度降低。冻融过程中,土样中水体积的变化使其密度减小、孔隙率增大是造成这一结果的原因。
Ball-shaped template press-in instrument (ball mold) in the former Soviet Union and Russia and other permafrost soil properties of the test has been widely used. In 60 years of engineering practice, experimental theory, methods and other aspects have been perfected. Because of its simple and easy test and the test results can well reflect the mechanical properties of frozen soil, especially in frozen soil cohesion long-term strength evaluation and prediction widely used. Brief introduction of the test theory, test methods, test equipment. Taking moraine silty clay on the outskirts of Moscow as the research object. Under the condition of constant temperature of -7 ~ 20 ℃, 3, 6, 20, 40 freeze-thaw cycles were carried out in closed condition respectively. The physical properties of the soil samples were tested at each test stage, and then the strength of the frozen soil samples was tested with a ball mold instrument. After freezing and thawing, the physical indexes of soil samples all decreased in different degrees, and their strength decreased with the increase of the number of freeze-thaw cycles. During the freeze-thaw process, the change of water volume in the soil sample decreases the density and the increase of the porosity is the reason of this result.