Variation of the modulus of elasticity of a collapsible soil of Petrolina-PE with and without flood

ABSTRACT Collapsible soils are unsaturated soils that undergo radical rearrangement of particles and great reduction of volume when wetting, with or without additional load application. These soils present serious problems for Geotechnical Engineering when there is a change of water content, causing additional deformations to the soils. The analysis of their behavior becomes an essential step for the success of an engineering project. Single and double edometric tests with controlled suction and the use of the Expanso-colapsometer were widely used to analyze the volume variation of the collapsible soils due to the change of water content , since they allow to evaluate the behavior of the collapsible soils in a way that simulate the conditions to which the soil will be submitted. The objective of this paper is to evaluate the elastic modulus in field of a collapsible soil of a residential complex in Petrolina-PE, with and without previous wetting. It was used in the field the Light Weight Deflectometer - LWD that is modern equipment that application load dynamic in a plate to the ground and allows measuring the deflections and quantifies the modulus of elasticity. The physical characterization of the soil was performed in the laboratory. The result showed a predominantly sandy soil with a modulus of elasticity ranging from 46.3 to 79.2 MPa and the wetting causes a reduction of 88%. In addition, it was found that the increase of moisture associated with the application of the dynamic load causes a reduction of its stiffness, occurring a decrease of the modulus of elasticity and, consequently, an increase of the deflection. From the results of the LWD, a criterion of identification of collapsible soil was established through the KLWD coefficient, attesting that Petrolina’s soil presents the following susceptibility to collapse: high for KLWD> 4.2, low for KLWD <2.8 and medium For KLWD between 2.8 and 4.2.

摘要：湿陷性土（Collapsible soils）属于非饱和土，在受水浸湿时（无论是否施加额外荷载）会发生颗粒结构的剧烈重组，并伴随体积的大幅缩减。这类土在含水量发生变化时会引发严重的岩土工程问题，导致土体产生附加变形，因此对其受力变形特性的分析是保障工程项目成功的关键环节。此前，控制吸力的单、双固结试验以及湿陷仪（Expanso-colapsometer）的应用被广泛用于分析湿陷性土因含水量变化引发的体积变形特性，因为这类试验方法能够模拟土体实际承受的工况，从而准确评估湿陷性土的工程响应。本文以佩特罗利纳-PE（Petrolina-PE）某住宅小区的湿陷性土为研究对象，旨在评估该土体在受水浸湿前后的现场弹性模量。现场测试采用了轻型弯沉仪（Light Weight Deflectometer, LWD），该设备属于现代化测试仪器，通过向地基施加动态板载荷载，可精准测量土体弯沉并量化其弹性模量。土体的物理性质表征试验在实验室完成。试验结果表明，该土体以砂质成分为主，弹性模量介于46.3 MPa至79.2 MPa之间；受水浸湿后，弹性模量降幅可达88%。此外，研究发现，含水量提升与动荷载施加共同作用会导致土体刚度降低，表现为弹性模量减小、弯沉值增大。基于轻型弯沉仪的测试结果，本文通过KLWD系数建立了湿陷性土的识别判据，证实佩特罗利纳地区土体的湿陷敏感性可按如下标准划分：当KLWD>4.2时为高敏感性，当KLWD<2.8时为低敏感性，当KLWD介于2.8与4.2之间时为中等敏感性。