The disposal of peat soil poses an increasingly difficult problem for actual engineering projects of Dianchi Lake area. This study obtains peat soil from seven areas around Dianchi Lake, and the content of humic acid (HA) in peat soil is between 2.36% and 28.13%. Then, this study simulates the peat soil by adding HA into the cohesive soil and uses cement to solidify it. The effect of cement and HA on the strength development of samples is examined by the unconfined compressive strength (UCS) test. Additionally, the microstructures of typical mixes are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The results showed that HA will significantly reduce the UCS of cement soil. The SEM, XRD, and MIP confirmed that cement hydration reaction increases with cement ratio. In addition to the cementitious soil particles, hydration products gradually fill the pores of the soil and effectively reduce the number of large-size (6000∼40,000 nm) pores in cement soil, which makes the soil particle framework stronger. When the cement ratio increases from 15% to 25%, the diffraction peak of CAH and CSH increases faster. Combined with the results of the UCS test, it could be proved that cement ratio greater than 20% weakens the influence of HA on the strength development of cement soil sample.

The effect and feasibility of peat soil environment (PSE) simulation pose a difficult problem for geotechnical environmental engineering. In this study, the actual content of humic group (HG) in peat soil of Dianchi Lake is determined, and the method of adding humic acid (HA) reagent into cohesive soil and soaking it in fulvic acid (FA) solution is used to simulate PSE of Dianchi Lake. By comparing the HG content of test samples and natural peat soil, the effect and feasibility of simulation test are studied. And the effects of HG on microstructure and material composition of PSE are analyzed by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) tests. The test results show that the content of HG and its components of PSE in seven sites of Dianchi Lake are quite different. The simulation method used in this study can simulate the PSE with different HA and FA contents, but the simulation method of soaking samples in FA solution cannot reach the actual effect. The SEM test confirm that the pore size and pore connectivity will increase with the HA reagent. However, FA is wrapped on the skeleton of soil through adsorption and fills some pores, which reduces the pore diameter and weakens pore connectivity. The XRD test shows that both HA and FA can reduce the diffraction peak of main substances in the samples, but not including SiO₂. The reason is that HG and cohesive soil particles undergo coordination exchange and ion exchange; free HG combines with cohesive soil particles and transforms into bound HG, forming an organic‐inorganic complex PSE.

Dolomite is a common type of natural soluble rock. The strength of rock decreases under the action of corrosion, which has a significant impact on the self-stability and long-term safety of the tunnel surrounding the rock. To reveal the microscopic structure evolution and strength-damage law of carbonate rock caused by chemical corrosion, a series of tests such as rock chemical corrosion test, rock uniaxial compression test and electron microscope scanning test are conducted at different pH values on the dolomite of the Doushantuo Formation. The rock dissolution at different pH values exhibits four typical stages: the initial dissolution stage, secondary dissolution acceleration stage, stable dissolution rate stage and dissolution attenuation stage. During the dissolution process, the initial dissolution rate is 25.91 times that of the stable stage, and the maximum strength attenuation is 76.2% after 21 days of dissolution. For macroscopic failure, the rock is developed from 1 to 2 external fractures to multiple internal and external fractures and penetrated, and the specimen transforms from brittle to flexible. For microstructure, the sample exhibits corrosion characteristics along the joint surface, intensified corrosion at the edge, etc. The porosity increase rate is 0.6%/d; however, the length–width ratio of the pores is maintained at 1.7–1.85, indicating that the development rate of pores in different directions is similar. The results of this study have enriched the study of the dolomite dissolution mechanism and, in addition, have important reference value for the stability evaluation of tunnel surrounding rock in karst environments.

To study the influence of water–rock interactions on the deterioration of rock, particularly the problems of the complex dissolution mechanism of dolomite and the difficulty in establishing chemical damage, dolomite obtained from a tunnel in Yuxi City was utilized. The macroscopic and microscopic dissolution characteristics of dolomite were analyzed using an indoor dissolution test combined with the hydrochemical characteristics of the study area, which were found to be favorable for dissolution. The dissolution of dolomite indicates the chemical decomposition of dolomite crystals, and the crystal failure mode is divided into intergranular dissolved pores and intracrystalline micropore development. Under various pH conditions, as H + is immersed in the rock sample, the failure mode of the rock sample develops from longitudinal cracks to transverse and longitudinal staggered cracks. Based on the aforementioned conclusions, in addition to the principle of chemical kinetics and the generalized Lemaitre strain equivalence principle, a damage model suitable for dolomite chemical erosion was defined. The fitting degree between the calculated value of uniaxial compressive strength and the experimental value reaches 98%, which is of excellent prediction accuracy and reliability. The model for dolomite chemical damage proposed herein provides a theoretical basis for dolomite dissolution damage; the theory of rock chemical damage is thereby enhanced.

Nanhong agate has attracted public attention as the most distinctive gemstone in China. Owing to the limited data on Nanhong agates from a new production area in northeastern Yunnan, this paper presents the first data from gemological studies on these agates. Complex investigations using Fourier-transform infrared (FTIR) spectrometry, ultraviolet–visible (UV–VIS) luminescence spectrometry, Raman spectroscopy, polarizing microscopy, scanning electron microscopy (SEM), electron microprobe (EPMA), and laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses were carried out to obtain basic data concerning the gemological properties, microstructure, and spectroscopic and geochemical characteristics of this interesting material. The results illustrate that Nanhong agates from northeastern Yunnan are mainly composed of α-quartz and also contain certain amounts of moganite, illite, goethite, and hematite. The typical red (yellow) and white appearance can be attributed to the microstructure of the agates, the contents of Fe and Al impurities, and trace elements. The Raman spectra, microstructure, and chemical composition of the unique “yellow-skinned” agates from northeastern Yunnan are significantly different from those of other types of Nanhong agate. This work lays a foundation for the future identification and research of this type of Nanhong agate.

To study the corrosion behavior of cement soil in peat soil, the experiment involves the preparation of peat soil by incorporating humic acid into cohesive soil with a lower organic matter content. Cement soil samples are then prepared by adding cement to the mixture. These samples are subjected to immersion in fulvic acid solution and deionized water to simulate different working environments of cement soil. The experiment considers immersion time as the variable factor. It conducts observations of apparent phenomena, ion leaching tests, and unconfined compression strength tests on the cement soil. The experiment results are as follows: (1) With increasing immersion time, the surface of the cement soil in the peat soil environment experiences the disappearance of Ca(OH)₂ and calcium aluminate hydrate. Additionally, large amounts of bird dropping crystals precipitate on the surface and within the specimen. The cement soil undergoes localized disintegration due to extensive erosion caused by swelling forces. (2) In the peat soil environment, fulvic acid reacts with the hydration products of cement, resulting in partial leaching of ions such as Ca²⁺, Mg²⁺, Al³⁺, and Fe³⁺ into the immersion solution. The lower the pH of the fulvic acid immersion (indicating higher concentration), the more significant the ion leaching. Increasing the ratio of humic acid to cement can slow down the leaching of ions. The cement soil undergoes dissolutive erosion in the peat soil environment. (3) The peat soil environment exerts both strengthening and corrosive effects on the cement soil. Cement soil without humic acid exhibits noticeable corrosion in the peat soil environment, gradually decreasing strength as immersion time increases. The strength decreases by 83% from 28 to 365 days. In contrast, cement soil with humic acid experiences an initial period of strengthening, leading to a significant increase in strength in the short term (34% increase from 28 to 90 days). However, the corrosive effects gradually dominate, resulting in a decrease in strength over time. The strength decreases by 80% from 90 to 365 days. This study also explores the strengthening effects of peat soil on cement soil. It identifies phenomena such as extensive erosion and new substance precipitation in cement soil.