大型土(石)方工程施工组织及造价影响分析

结合机场大型土(石)方工程的施工特点,在施工组织设计(方案)编制中应重点考虑土(石)方开挖分区,调配运输方案,爆破作业方法,施工机具组合、临时排水措施等问题,从而确定合理的工程造价。

土(石)方工程设计若干问题探讨

结合工程实践,对化工企业总图运输专业有关场地土(石)方工程设计计算方面的若干问题进行了讨论,对现行的化工企业总图运输设计规范有关条款提出了建议。

浅谈公路投标过程中路基土（石）方运距的确定

投标过程中在时间较紧的情况下，对土（石）方运距的确定难度较大。本文结合投标经验，论述了根据标书中提供的资料，确定土石方综合运距的方法。

城市规划设计中土(石)方计算问题探讨

本文分别对不同规划编制过程中土(石)方计算的可行性和必要性进行分析,并对土(石)方计算依据、目的、内容、深度要求等问题进行了探讨。在多年规划设计实践的基础上,总结提出在修建性详细规划中土(石)方计算中应该注意的几个问题,并提出对策。

Chao HUANG,Main Factors Affecting the Improving Efficiency of Gypsum for Solonetzic Soil

In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, alkaline salt content, optimal irrigation, gypsum conversion, gypsum and soil treatment and improvement depth. The ions on the obtained filtrate were analyzed in terms of salts. The improving ef- ficiency of gypsum for meadow alkali soil was analyzed through comparing the con- tents of soluble salts in pre-improvement and post-improvement soil by reasoning and calculation. The results showed that, （1） the dissolved amount and conversion amount of gypsum were increased, and the soil alkalinity was decreased corre- spondingly with the increased irrigation amount. However, after reaching a certain extent, the linear relationships became unobvious gradually. Therefore, the irrigation amount should be arranged reasonably for different treatment. （2） Compared with those at low temperature, the dissolved amount of gypsum at high temperature was increased by 1.47-1.50 times, the release amount of exchangeable sodium was in- creased by 2.98-4.70 times, and the release amount of exchangeable magnesium was increased by 2.07-2.90 times. In overall, the improving efficiency of gypsum in summer was better. However, gypsum had two shortcomings in summer. First, a large amount of gypsum leaked away. Second, a large amount of exchangeable magnesium, along with exchangeable sodium, was substituted by gypsum. （3） Compared with the other two treatments, treatment B （mixing gypsum and top 20- cm soil） showed the best improving efficiency, and it was characterized by stepwise dealkalization from top to down. In addition, mixing gypsum and topsoil is more practical in the production.

变电站竖向布置设计

竖向布置设计对节约用地、基本投资、建设进度、安全生产、运营管理有非常重要的影响。介绍了竖向布置的任务及设计内容,结合工程实践,充分分析了洪水水位、进站道路、竖向布置方式、土(石)方工程量、护坡、挡土墙等对变电站竖向布置设计的影响作用,提出设计中应根据工程实际情况,综合考虑多种因素,尽量优化竖向布置设计,使竖向布置方案经济合理、节约环保。

Fuzzy Earthwork Dynamic Allocation and Optimization for Construction of High Concrete Face Rockfill Dam

Due to the complexity of earthwork allocation system for the construction of high concrete face rockfill dam,traditional allocation and planning are not able to function properly in the construction process with strong randomness.In this paper,the working mechanism of earthwork dynamic allocation system is analyzed comprehensively and a solution to fuzzy earthwork dynamic allocation is proposed on the basis of uncertain factors in the earthwork allocation of a hydropower project.Under the premise of actual situation and the experience of the construction site,an all-coefficient-fuzzy linear programming mathematical model with fuzzy parameters and constraints for earthwork allocation is established according to the structure unit weighted ranking criteria.In this way,the deficiency of certain allocation model can be overcome.The application results indicate that the proposed method is more rational compared with traditional earthwork allocation.

浅谈新建溢洪道的施工工艺

介绍了溢洪道的主要组成部分,简要阐述了总体的施工程序及施工工艺,为以后类似工程施工提供参考。

The construction design and practice of Three Gorges Project

The construction of Three Gorges Project (TGP) is characterized by large construction scale,high construction intensity and complexity in technology.In view of various technical difficulties such as navigation in construction period,two river closures,high-intensity concrete and earth-rock construction,high-intensity construction and demolition of RCC (roller compacted concrete) cofferdam in stage III and immediate navigation of double-line five-step shiplock after impoundment of reservoir,the scheme of river diversion during construction is adopted,namely "diversion in 3 stages,open channel navigation and cofferdam power generation".The practice and innovation achievements in river diversion during construction as well as earth-rock and concrete construction are presented emphatically.

Effects of slope position and land use on the stability of aggregateassociated organic carbon in calcareous soils

Topography and land use affect soil organic carbon(SOC) storage, stabilization, and turnover, through several biogeochemical processes. This study investigated the aggregate composition and SOC content of bulk soils and aggregates at different slope positions under different land uses in a typical karst catchment of southwestern China. Our results show that the proportion of macro-aggregates and the SOC content of bulk soils and aggregates at different slope positions decreased from the upper to the lower slope. The SOC content generally increased with an increase in the mean weight diameter and proportion of macro-aggregates under different land uses. Our results indicate that macro-aggregates in forest and grassland soils make a greater contribution to both aggregate composition and SOC content than that in arable land soils. Therefore,converting farmland to forest or grassland can facilitate the accumulation of macro-aggregates as well as the storage of SOC.

Process optimization and kinetics for leaching of cerium, lanthanum and neodymium elements from iron ore waste's apatite by nitric acid

The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid ratio and 38 min leaching time. The kinetics of cerium leaching was investigated using shrinking core model. It was observed that the leaching is composed of two stages. In the first stage a sharp increase in cerium leaching recovery was observed and at the longer time the leaching became slower. It was found that in the first stage the diffusion of reactants from ash layer is the rate controlling mechanism with an apparent activation energy of 6.54 kJ/mol, while in the second stage the mass transfer in the solution is the controlling mechanism.

Sequestration of carbon as carbonate in the critical zone：insights from the Himalayas and Tibetan Plateau

The carbon pool stored in soil carbonate is comparable to the soil organic carbon.Therefore,secondary calcite precipitation in supersaturated catchment could be an important,yet poorly constrained,carbon sink within the modern global carbon cycle.The chemical analysis of some dissolved species transported by rivers,such as elevated Sr/Ca and Mg/Ca ratios but also heavy stable Ca isotopic compositions,witness the formation of secondary calcite in rivers draining arid regions.However,in areas affected by active tectonics and rapid physical erosion,co-variations in the fluvial Sr/Ca and Mg/Ca ratios could also be related to incongruent carbonate weathering processes.Here,we present a model to assess the roles played by incongruent carbonate dissolution and secondary calcite precipitation in modern weathering processes.We tested and applied the model to rivers draining the Himalayan–Tibetan region.The results suggest that regional aridity in the drainage basin promotes carbon sequestration as secondary carbonate but that for a given runoff,incongruent dissolution of carbonate possibly related to rapid physical erosion amplifies such sequestration.The isotopic compositions(^(13)C/^(12)C and^(18)O/^(16)O)of detrital carbonate transported by the main rivers in South and South-East Tibet imply that around 1%of the suspended material transported by those rivers corresponds to secondary carbonate and can represent between 5%and 15%of the alkalinity flux.Most of these alkalinity transported as particulate material is,nevertheless related to the weathering of carbonate lithologies and is also subjected to dissolution prior its final storage in sedimentary basins.However,on glacial-interglacial timescale this will amplify the significant role of mountain weathering on climatic variations.

A Novel Method for the Fabrication of Granular Hydroxyapatite-bentonite Composite Adsorbents for the Removal of Pb2＋ from an Aqueous Solution

Granular HApB composite adsorbents, with dimensions of 4 mm × 4 mm, were prepared for the removal of lead from an aqueous solution. The effectiveness of the composites for Pb2＋ removal from an aqueous solution with different initial concentrations, adsorbent doses and reaction times were examined. The Langmuir isotherms, Freundlich isotherm models and pseudo-second order kinetic model were used in this analysis. It was found that the Langmuir model fitted the experimental data better than the Freundlich model, with a maximum adsorption capacity of 93.37 mg.g-1. The pseudo-second order kinetic model also fit the experiment data well with an adsorption capacity of 70.73 mg.g-1 after being reused for 3 times. Furthermore, the composites may possibly be used in processes for industrial water treatment.

某招标工程量清单项目特征描述缺项案例所引发的思考

一、项目基本情况2021年下半年,项目业主对位于陕西省宝鸡市的某房屋建筑工程项目组织了施工招标,在完成相关程序后,施工单位正式进场施工。由于该项目的原有地貌为游泳池,2022年初,施工单位在土(石)方回填过程中,出现挖土方后原有土方量不足以回填土方的情况,导致施工单位需要外购黄土进行土(石)方回填作业。

Effect of permafrost degradation on hydrological processes in typical basins with various permafrost coverage in Western China

Monthly discharge of four rivers with various permafrost coverage and little anthropogenic influence was used to identify effects of permafrost degradation during the last 50 years,which has occurred because of significant increases in air temperature in the river regions.The basins of the Shule,Heihe,Shiyang and upper Yellow Rivers in northwestern China have 73%,58%,33% and 43% permafrost coverage,respectively.There is snow cover in the basins and no rain to supply rivers during winter. The monthly recession coefficient(RC) in winter reflects groundwater conditions.The RC has increased obviously for the Shule and Heihe rivers with 73% and 58% permafrost coverage,respectively,but did not increase for the Shiyang River,and decreased insignificantly for the upper Yellow River,which had less permafrost coverage.There is a distinct positive relationship between RC and annual negative degree-day temperature(NDDT) at the meteorological stations in the basins with high permafrost coverage.These results imply that permafrost degradation due to climate warming affects hydrological processes in winter.The effect is obvious in the basins with high permafrost coverage but negligible in those with low permafrost coverage. Permafrost degradation increases infiltration,enlarges the groundwater reservoir,and leads to slow discharge recession.The result means that hydrological processes are affected strongly by permafrost degradation in river basins with high permafrost coverage,but less in river basins with less permafrost coverage.

Clay Addition to Sandy Soil Influence of Clay Type and Size on Nutrient Availability in Sandy Soils Amended with Residues Differing in C/N ratio

Addition of clay-rich subsoil to sandy soil results in heterogeneous soil with clay peds （2-mm） or finely ground （〈 2 mm） clay soil （FG）, which may affect the nutrient availability. The aim of this study was to assess the effect of clay soil particle size （FG or peds） and properties on nutrient availability and organic C binding in sandy soil after addition of residues with low （young kikuyu grass, KG） or high （faba bean, FB） C/N ratio. Two clay soils with high and low smectite percentage, clay and exchangeable Fe and A1 were added to a sandy soil at a rate of 20% （weight/weight） either as FG or peds. Over 45 d, available N and P as well as microbial biomass N and P concentrations and cumulative respiration were greater in soils with residues of KG than FB. For soils with KG residues, clay addition increased available N and initial microbial biomass C and N concentrations, but decreased cumulative respiration and P availability compared to sandy soil without clay. Differences in measured parameters between clay type and size were inconsistent and varied with time except the increase in total organic C in the 〈 53 μm fraction during the experiment, which was greater for soils with FG than with peds. We concluded that the high exchangeable Fe and A1 concentrations in the low-smectite clay soil can compensate a lower clay concentration and proportion of smectite with respect to binding of organic matter and nutrients.

SHRIMP zircon age for a K-bentonite in the top of the Laobao Formation at the Pingyin section,Guizhou,South China

The Lower Cambrian on the Yangtze Platform in South China （internationally equivalent to the Nerreneuvian and 2nd series of the Cambrian） is valuable for understanding the early evolution of life, the global biogeochemical circles, and the major changes of the ocean. In particular, a precise radiometric calibration of the Lower Cambrian of this region is a critical realm in its multidisciplinary studies. A SHRIMP U-Pb geochronology study of the K-bentonite in the topmost Laobao Formation at the Pingyin section, Guizhou, South China yielded an age of 536±5 Ma （MSWD -- 0.75）, suggesting that the K-bentonite here can be correlated with the intensely studied K-bentonite within the middle Zhongyicun Member （Bed 5） of the Zhujiaqing For- mation at the Meishucun section in Yunnan. Such a regional correlation result reveals that the Bed 5 K-bentonite also extends into deeper-water environments rather than being deposited merely in the shallow platform interior of the Yangtze Platform. The age of the K-bentonite at the Pingyin section also implies that its overlying polymetallic Ni-Mo layer should be younger than 536e5 Ma. Hence the previous placement of the Precambrian/Cambrian boundary at this layer is inappropriate. Combined with the results of stratigraphic correlations, it is suggested that the K-bentonites in the middle Zhongyicun Member of the Zhujiaqing Formation （or the equivalents） and the base of the Shiyantou Formation （or its equivalents）, together with the polymetallic Ni-Mo layer, serve as three important marker beds. Their self-consistent radiometric ages have established an im- proved geochronologic framework for the Lower Cambrian in South China.