The underlying mechanism of variety–water–nitrogen–stubble damage interactions on yield formation in ratoon rice with low stubble height under mechanized harvesting

Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.

Deformation mechanism and roof pre-splitting control technology of gob-side entry in thick hard main roof full-mechanized longwall caving panel

This paper explores the deformation mechanism and control technology of roof pre-splitting for gob-side entries in hard roof full-mechanized longwall caving panel(LTCC).The investigation utilizes a comprehensive approach that integrates field monitoring,theoretical analysis,and numerical simulation.Theoretical analysis has illuminated the influence of the length of the lateral cantilever beam of the main roof(LCBM)above the roadway on the stability of the gob-side entry behind the panel.Numerical simulations have further revealed that the longer LCBM results in heightened vertical stress within the coal pillar,developed cracks around the roadway,and more pronounced damage to the roadway.Moreover,numerical simulations also demonstrate the potential of roof pre-splitting technology in optimizing the fracture position of the hard roof.This technology significantly reduces the length of the LCBM,thereby alleviating stress concentration in the coal pillars and integrated coal rib while minimizing the destruction of the gob-side entry.Therefore,this manuscript first proposes the use of roof pre-splitting technology to control roadway deformation,and automatically retain the entry within a hard roof LTCC panel.Field implementation has demonstrated that the proposed automatically retained entry by roof pre-splitting technology effectively reduces gob-side entry deformation and achieves automatically retained entry.

Stability evaluation method of large cross-section tunnel considering modification of thickness-span ratio in mechanized operation

Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.

Strategies and Suggestions for the Development of Mechanized Rapeseed Production in Sichuan

Mechanization is the future direction of rapeseed production in Sichuan. A series of technology tests for rapeseed mechanized production have been carried out in terms of variety selection, key agronomic measures and machinery in the main production area of Sichuan in recent years. In the research, the agronomic techniques, including variety selection for mechanical production, key agronomic measures and mechanical harvesting were analyzed. Based on the present condi- tions, strategy and suggestions for the development of mechanized rapeseed produc- tion in Sichuan also were presented.

Development and prospect on fully mechanized mining in Chinese coal mines

Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced.The automatic FMM technology for thin seams,complete sets of FMM technology with ultra large shear height of 7 m for thick seams,complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m,complete sets of FMM technology for complex and difficult seams,including steeply inclined seams,soft coal seams with large inclination angle,and the mechanized filling mining technology and equipment are presented.Some typical case studies are also introduced.Finally,the existing problems with the FMM technology are discussed,and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.

Research Progress on Mechanized Mixed Sowing Seed Production Technology of Hybrid Rice

Hybrid rice planting has been widely popularized and applied in the world. However, the high cost of seed production and the complicated procedures have become a bottleneck in the development of hybrid rice. The research progress on mixed sowing seed production techniques of hybrid rice was introduced from the aspects of rice resources creation, breeding, sowing seed technology research and cost benefit analysis. The production technology of the new mixed seeding combina- tion ＂Xinhunyou 6＂ was investigated, including the research and validation of benta- zon treatment period and dosage, mixing ratio of male and female parents, and the comparative test of different different sowing methods, which revealed that the mechanization technology of seed production of hybrid rice was mature and feasible and would be one of the most important development trend of technological devel- opment of hybrid rice production.

Effects of Mechanized Transplanting and Fertilization Mode on Population Growth and Development of Male Parent in Seed Production of Hybrid Rice

In order to study the effects of mechanized transplanting and fertilization mode on population growth and development of the male parent in seed production of hybrid rice, three male parents, Huazhan, Shuhui 527 and R9311 were selected as materials. The male parents were transplanted by rice transplanter with two kinds of line spacing design, six lines with equal row spacing （20/25 cm x 30 cm） and wide and narrow spacing （20/25 cm x 40, 20 cm）, and artificial transplanting with equal row spacing （20/25 cm x 30 cm） was set as the control. The three fer- tilization modes were applying for one, two and three times. The flowering stage and panicle-spikelet structure of the male parent were investigated. The results showed that the effects of mechanized transplanting and fertilization mode were little on the duration from seeding to heading; the panicles and spikelets of the three male parents were significantly increased by mechanized transplanting. The tiller number was increased by mechanized transplanting and fertilizing for two and three times. Wide and narrow spacing by machine planting and fertilizing for three times were suitable for Huazhan, which significantly increased the number of spikelets per unit area. Furthermore, the number of spikelets per unit area of Shuhui 527 and R9311 were significantly increased by mechanized transplanting and fertilizing for three times.

Effects of Key Agricultural Measures of Mechanized Direct Seeding Technology on Rapeseed Yield in Chengdu Plain

Mechanized direct sowing of rapeseed is a labor-saving and highly-efficient culture technique. In order to explore high-yield cultivation techniques suitable for Chengdu Plain, effects of several key agronomic measures＇, such as sowing date, density and N fertilizers, on development and yield formation were studied by strip and split plot experiment of three factors. The research showed that optimal condi- tions for direct seeding technology can be achieved provided with scientific sowing date, density and appropriate N fertilizers, and the research showed that rapeseed yield reached the peak at 320 g/m2, when sowing date was on September 3th, sow- ing density was 30 plant/m2, and nitrogen fertilizer was 27 g/m2.

Comparison of yield traits in rice among three mechanized planting methods in a rice-wheat rotation system

Understanding the differences in yield traits of rice among pothole seedling of mechanical transplanting （PSMT）, carpet seedling of mechanical transplanting （CSMT） and mechanical direct seeding （MDS） is of great importance not only for rice scientists but also for rice farmers to develop a high-yield production system under mechanical conditions in a rice-wheat rotation system. However, such traits are yet to be studied among rice varieties ofjaponica-indica hybrid rice （JIHR）,japonica conventional rice （JCR） and indica hybrid rice （IHR）. Field experiments were conducted in 2014 and 2015, where six cultivars of the three rice types JIHR, JCR and IHR were grown individually with PSMT, CSMT and MDS methods, under respective managements for each method to achieve the maximum attainable yield. Results showed that （i） the PSMT significantly increased grain yield of JIHR by 22.0 and 7.1%, of JCR by 15.6 and 3.7% and of I HR by 22.5 and 7.4%, compared to MDS and CSMT on average across the two years, respectively. The highest yield was produced by the combination of JIHR and PSMT; （ii） high yield under PSMT was mainly attributed to large sink capacity and high-efficient dry matter accumulation. With sufficient panicles per hectare, the increase of spikelet number per panicle, especially the increase in spikelet number of the secondary rachis-branches was determined to be the optimal approach for developing a large sink capacity for rice under PSMT. The optimal tillers development, large leaf area index at heading stage, and high leaf area duration, crop growth rate and net assimilation rate during grain-filling phase could be the cause of sufficient dry matter accumulation for rice under PSMT; （iii） moreover, the PSMT favored plant growth as well as enriched the stems plus sheaths during grain-filling phase, as compared with CSMT and MDS. These results suggest that PSMT may be an alternative approach to increasing grain yield in a rice-wheat rotation system in the lower reaches of the Yangtze River in China.

Mining pressure monitoring and analysis in fully mechanized backfilling coal mining face-A case study in Zhai Zhen Coal Mine

Fully mechanized solid backfill mining(FMSBM) technology adopts dense backfill body to support the roof. Based on the distinguishing characteristics and mine pressure control principle in this technology, the basic principles and methods for mining pressure monitoring were analyzed and established. And the characteristics of overburden strata movement were analyzed by monitoring the support resistance of hydraulic support, the dynamic subsidence of immediate roof, the stress of backfill body, the front abutment pressure, and the mass ratio of cut coal to backfilled materials. On-site strata behavior measurements of 7403 W solid backfilling working face in Zhai Zhen Coal Mine show that the backfill body can effectively support the overburden load, obviously control the overburden strata movement, and weaken the strata behaviors distinctly. Specific performances are as follows. The support resistance decreases obviously; the dynamic subsidence of immediate roof keeps consistent to the variation of backfill body stress, and tends to be stable after the face retreating to 120-150 m away from the cut. The peak value of front abutment pressure arises at 5-12 m before the operating face, and mass ratio is greater than the designed value of 1.15, which effectively ensures the control of strata movement. The research results are bases for intensively studying basic theories of solid backfill mining strata behaviors and its control, and provide theoretical guidance for engineering design in FMSBM.

Mechanized Seed Production of Xinhunyou No.6 through Mixed Seeding of Parents' Seeds

Hybrid rice Xinhunyou No. 6 could be cultivated by mixing male and fe- male parents and performing seedling raising followed by transplanting, mechanical planting or mechanical direct seeding according to the production methods of com- mercial rice. During flowering stage, leaf cutting, application of ＂920＂ and pollination were conducted; after pollination, bentazon with a certain concentration was sprayed to kill the male parent; and the hybrid rice was harvested mechanically. Before storage, color separation was performed to remove little remaining male parent, thereby achieving whole-process mechanization of hybrid rice seed production. This study introduced mechanized seed production of Xinhunyou No. 6 through mixed- seeding from the aspects including mechanical direct seeding, seeding raising fol- lowed by transplanting and mechanical planting.

Determination of optimal blowing-to-suction flow ratio in mechanized excavation face with wall-mounted swirling ventilation using numerical simulations

Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models were developed according to the No.C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau,Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling ventilation.Both the k-εturbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow ratios.The results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air curtain.On the other hand,both the intensity of the radial air curtain and the dust suppression effect are enhanced.At a blowing-to-suction flow ratio of 0.8,the wall-mounted swirling ventilation system achieved the most favorable dust suppression performance.Both the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33%and 87.16%,respectively.

Fracture mechanics model of fully mechanized top coal caving of shallow coal seams and its application

Based on break characteristics of roofs in fully mechanized top-coal mining of thick shallow coal seams, a fracture mechanics model was built, and the criterion of crack propagation in the main roof was derived using the fracture mechanics theory. The relationships between the fracture length of the roof and the working resistance of the supports were discovered, and the correlations between the load on the overlying strata and the ratio of the crack's length to the thickness of the roof were obtained. Using a working face of Jindi Coal Mine, Xing county Shanxi province as an example, the relationships between the fracture length of the roof and the working resistance of the supports were analysed in detail. The results give a design basis in hydraulic top coal caving supports, which could provide useful references in the practical application. On-site experiment proves that the periodic weighting step interval of the caving face is 15–16 m, which is basically consistent with the theoretical analysis results, and indicates that the mechanized caving hydraulic support is capable of meeting the support requirements in the mining of a super-thick but shallowly buried coal seam.

Deformation mechanism of surrounding rocks and key control technology for a roadway driven along goaf in fully mechanized top-coal caving face

The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.

Mechanized Tunneling in Soft Soils： Choice of Excavation Mode and Application of Soil-Conditioning Additives in Glacial Deposits

The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of sound and altered rock, as well as to inhomogeneous soil layers that range from permeable gravel to soft clay sediments along the same tunnel. This article focuses on past experiences with tunnel-boring machines （TBMs） in Switzerland, and specifically on the aspects of soil conditioning during a passage through inhomogeneous soft soils. Most tunnels in the past were drilled using the slurry mode （SM）, in which the application of different additives was mainly limited to difficult zones of high permeability and stoppages for tool change and modification. For drillings with the less common earth pressure balanced mode （EPBM）, continuous foam conditioning and the additional use of polymer and bentonite have proven to be successful. The use of conditioning additives led to new challenges during separation of the slurries （for SM） and disposal of the excavated soil （for EPBM）. If the disposal of chemically treated soft soil mate- rial from the earth pressure balanced （EPB） drive in a manner that is compliant with environmental legislation is considered early on in the design and evaluation of the excavation mode, the EPBM can be beneficial for tunnels bored in glacial deposits.

Analysis and key control technologies to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines

In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China, we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion, such as rock bursts, high temperatures, high ventilation resistance, slow advancing speed and large obliquity mining. Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are pro- posed; these include pouring water, stopping leakage in upper and lower comers of the working face, choking off the goaf and cov- eting the coal. CO concentrations were controlled within two years to less than 15×10^-6 at the upper comer by applying these tech- nologies at the 1410 working face of the Huafeng coal mine. Our method has significant theoretical value and is of practical impor- tance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.

Development of dust collection and removal technology of comprehensive mechanized excavation face

To solve the problem of excavation face dust control,the theory of dust removal after collection was put forward.Through a large number of theoretical and experimental researches,a new wind screen dust-collection system which was applied to comprehen- sive excavation face was developed.To set a wind dam in jet stream box,achieve the function of multi-stage and multiple-level regulation,lots of experimentation was carried out to obtain higher jet stream velocity with the minimum loss of energy.Experiments show that the slit width in the exports of wind screen dust-collection system should be 10 to 15 mm.For the general excavation roadway,after wind attenuation,the velocity can be greater than 3 m/s at the roof which meets the requirements of respirable dust control.

Study of mechanical principle of floor heave of roadway driving along next goaf in fully mechanized sub-level caving face

Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata was calculated, the results showed that the high abutment pressure on coal mass beside the roadway was the main reason to lead to relative displacement of floor strata. And the roadway floor heave come mainly from three aspects. Firstly, the roadway floor strata is easily fractured by the stretch stress. Secondly, because the high abutment pressure is greater than the uniaxial compressive strength of floor strata, when the roadway floor strata are fractured, the coal mass floor strata at the same depth will be fractured, and broken rock will fluid into the open roadway. Thirdly, comparing with the coal mass floor, the roadway floor is relative ascending.

Application of deep borehole blasting on fully mechanized hard top-coal pre-splitting and gas extraction in the special thick seam

In order to solve the problems of top-coal inadequate destruction and large amounts of gas emission in mining extra thick and hard coal seam,this study investigated the pre-splitting for deep borehole blasting and gas pre-draining technologies on top coal.The mechanism of the technologies was systematically expounded based on hard top-coal cracks development obtained by numerical simulation and theoretical analysis.The results show that explosive blasting in the hard rock results in a large number of cracks and large displacement in the rock mass due to the effect of explosion stress.Meanwhile,the thick top-coal caves,and desorbing gas flows along the cracks improve gas extraction.Finally,the pre-splitting for deep borehole blasting and gas pre-draining technologies was applied in No.3802 working face of Shui Liandong Coal Mine,which increases monthly output in the face to 67.34 kt and the drained gas concentration to 86.2%.The drained gas average concentration from each borehole reaches 40%,and the effect is remarkable.

Backfilling technology and strata behaviors in fully mechanized coal mining working face

Based on the principle of fully mechanized backflling and coal mining technology and combined with the Xingtai Coal Mine conditions, we mainly optimized the coal mining equipment and adjusted the coal mining method in the Xingtai Coal Mine 7606 working face for implementation this technology. Firstly, we define the practical backfilling process as the ＂（from backfilling scraper conveyor＇s） head to tail back- filling, step by step swinging up of the tamping arm, gradual compacting, moving formed backfilling scra- per conveyor when the second tamping arm cannot pass and connecting the immediate roof by back material push front material movement＂. Meanwhile, the stress changes of backfill body in coal mined out area was monitored by stress sensors, and the roof caving law was analyzed by monitoring the dynamic subsidence of -210 west roadway of this face. The site tests results show that using this new backfilling and coal mining integrated technology, the production capacity in the 7606 working face can reach to 283,000 ton a year, and 282,000 ton of solid materials （waste and fly ash） is backfilled, which meets the needs of high production and efficiency. The goaf was compactly backfilled with solid material and the strata behavior was quite desirable, with an actual maximum vertical stress of the backfill body of 5.5 MPa. Backfill body control the movement of overburden within a certain range, and there is no col- lapses of major areas in the overlying strata upon backfilled gob. The maximum subsidence and speed were 231 mm and 15.75 mm/d respectively, which proved the practical significance of this integrated technology.