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石灰改良分散性土拌和工艺与压实特性
何建新, 高鹏展, 杨海华, 杨伟, 文军, 耿旭, 王宁远
raybet体育在线 院报 ›› 2025, Vol. 42 ›› Issue (3) : 118-124.
PDF(5476 KB)
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石灰改良分散性土拌和工艺与压实特性
Mixing Technique and Compaction Characteristics of Lime-improved Dispersive Soil
新疆某水库心墙坝用土为分散性土,设计采用掺1%石灰进行处理。为确保使用石灰改良分散性土的心墙坝工程质量,实现拌和的均匀效果,在碾压试验的基础上,使用ZB05型冷再生路拌机对石灰分别进行1、2、4、6次的拌和,通过SG-6型多功能直读式测钙仪随机快速检测土料石灰含量,对石灰改良土的均匀性进行质量控制;探究陈化时间对改良土击实特性的影响,并结合室内压缩和直剪试验研究现场施工环境下龄期对改良土物理力学性能的影响规律。结果表明:当碾压8遍且摊铺厚度为30、35 cm时,沉降量已基本稳定,干密度可满足≥1.73 g/cm3、压实度可满足≥99%的条件;在搅拌遍数为6时,拌和石灰的均匀性趋于稳定,变异系数为0.28;石灰改良土的陈化时间越长越不利碾压,按99%的压实度时评价陈化时间应≤9 h;改良土的压缩性和强度受龄期影响明显,龄期增大,石灰改良土的压缩性减小、抗剪强度增大,与室内试验规律相一致。研究成果可为采用石灰改良分散性土的工程提供理论支撑及参考。
The soil used for the core dam of a reservoir in Xinjiang is dispersive soil. To treat this soil, 1% lime is added. To ensure project quality and achieve uniform mixing, a ZB05 cold recycling paver was employed, with mixing cycles set at 1, 2, 4, and 6, respectively. The SG-6 multifunctional direct-reading calcium meter was used for rapid and random detection of soil lime content to control the uniformity of the lime-treated soil. The influence of aging time on the compaction characteristics of the improved soil was also investigated. In the field construction environment, the impact of curing age on the physical and mechanical properties of the improved soil was evaluated through indoor compression and direct shear tests. Results show that, when rolled 8 times with a spread thickness of 30 and 35 cm, the settlement of the soil material stabilizes, and the dry density after rolling meets the requirement of ≥1.73 g/cm3, with a compaction degree of ≥99%. When the mixing cycle is 6, the uniformity of the lime mixing stabilizes, with a coefficient of variation ( Cv ) of 0.28. As the aging time increases, the lime-treated soil becomes less favorable for rolling. To maintain a compaction degree of 99%, the aging time should not exceed 9 hours. The compressibility and shear strength of the improved soil are significantly influenced by curing age. As curing age increases, the compressibility of the lime-treated soil decreases, whereas shear strength increases, consistent with laboratory test results.
分散性土 / 碾压工艺 / 拌和工艺 / 陈化时间 / 龄期
dispersive soil / rolling process / mixing process / aging time / curing age
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Dispersive clay is a special soil which can be washed out by water easily. With the development of earth and rockfill dam, the range of choosing core material expands correspondingly. Dispersive clay as core material and its seepage-proofing effect under the protection of filters are issues concerned in engineering design. In this research we collected core materials from two stock grounds of a hydro-junction and conducted laboratory tests using pinhole, fragment, pore water solution and double areometers to determine the dispersibility of core material. By mixing different ratios of cement or quick lime, we modified the dispersibility of the core materials and compared their permeability and filter protection effect before and after modification. Results reveal that by mixing 3% of cement or 3%-5% of quick lime we can eliminate the dispersibility of the core materials from the two sites. Moreover, core material modified by cement or quick lime could bear higher hydraulic gradient than non-modified material does. Under the protection of proper filtration material, dispersive clay could bear high gradient, and has good self-healing ability in the presence of fissures.<br/><br/>
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Previous research results on the mechanism of expansive soil stabilized by lime are summarized. It is clear that cation exchange is the first reaction when lime is added into expansive soil, followed by flocculation and agglomeration. These reactions change the soil’s properties quickly. Pozzolanic reaction of lime and soil is a long-term process, which helps increase the strength of expansive clay. Carbonation and crystallization also contributes to the strength increase of expansive soil. Diffusion and cementation are the causes of interior changes in the soil. Microstructure and mineralogy changes are the internal causes of stabilization of expansive soils. Moreover, analysis on the quantitative cation exchange, quantitative microstructure change, and soil suction change of expansive soil during lime treatment would be new research focus. These investigations will further reveal the fundamental mechanism of expansive soil stabilized by lime. The review also indicates that the possible environmental pollution caused by lime stabilization can be ignored.
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