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1英文原文Mine hoisting in deep shafts in the 1st half of 21st CenturyAlfred Carbogno Key words: deep shaft, mine hosting, Blair winder, rope safety factor, drum sizing, skip factor Introduction The mineral deposits are exploited on deeper and deeper levels. In connection with this, definitions like “deep level” and “deep shaft” became more and more popular. These definitions concern the depth where special rules regarding an excavation driving, exploitation, rock pressure control, lining construction, ventilation, underground and vertical transport, work organization and economics apply. It has pointed out that the “deep level” is a very relative definition and should be used only with a reference to particular hydro-geological, mining and technical conditions in a mine or coal-field. It should be also strictly defined what area of “deep level” or “deep shaft” definitions are considered. It can be for example: (1)mining geo-engineering, (2)technology of excavation driving, (3) ventilation (temperature). It is obvious that the “deep level” defined from one point of view, not necessarily means a “deep level” in another area. According to 5 as a deep mine we can treat each mine if: (1)the depth is higher than 2300 m or (2)mineral deposit temperature is higher than 38 C. It is well known that the most of deep mines are in South Africa. Usually, they are gold or diamonds mines. Economic deposits of gold-bearing ore are known to exist at depths up to 5000 m in a number of South Africa regions. However, due to the depth and structure of the reef in some areas, previous methods of reaching deeper reefs using sub-vertical shaft systems would not be economically viable. Thus, the local mining industry is actively investigating new techniques for a single-lift shaft up to 3500 m deep in the near future and probably around 5000 m afterwards. When compared with the maximum length of wind currently in operation of 2500 m, it is apparent that some significant innovations will be required. The most important matter in the deep mine is the vertical transport and the mine 2hoisting used in the shaft. From the literature 1-12 results that B.M.R. (Blair Multi-Rope) hoist is preferred to be used in deep mines in South Africa. From the economic point of view, the most important factors are: (1)construction and parameters of winding ropes (safety factor, mainly), (2)mine hoisting drums capacity. This article of informative character presents shortly above-mentioned problems based on the literature data 1-12. Especially, the paper written by M.E. Greenway is very interesting 3. From two transport systems used in the deep shaft, sub-vertical and the single-lift shaft systems, the second one is currently preferred. (Fig.1.) 6 Hoisting Installation The friction hoist (up to 2100 m), single drum and the double drum (classic and Blair type double drum) hoist are used in deep shafts in South Africa. Drum winders Drum winders are most widely used in South Africa and probably in the world. Three types of winders fall into this category (1)Single drum winders, (2)Double drum winders, (3)Blair multi-rope winders (BMR). Double drum winders Two drums are used on a single shaft, with the ropes coiled in opposite directions with the conveyances balancing each other. One or both drums are clutched to the shaft enabling the relative shaft position of the conveyances to be changed and permitting the balanced 3hoisting from multiple levels The Blair Multi-Rope System (BMR) In 1957 Robert Blair introduced a system whereby the advantage of the drum winder could be extended to two or more ropes. The two-rope system developed incorporated a two-compartment drum with a rope per compartment and two ropes attached to a single conveyance. He also developed a rope tension-compensating pulley to be attached to the conveyance. The Department of Mines allowed the statutory factor of safety for hoisting minerals to be 4,275 instead of 4,5 provided the capacity factor in either rope did not fall below the statutory factor of 9. This necessitated the use of some form of compensation to ensure an equitable distribution of load between the two ropes. Because the pulley compensation is limited, Blair also developed a device to detect the miscalling on the drum, as this could cause the ropes to move at different speeds and so affect their load sharing capability. Fig.2 shows the depth payload characteristics of double drum, BMR and Koepe winders. The B.M.R. hoist is used almost exclusively in South Africa, probably because they were invented there, particularly for the deep shaft use. There is one installation in England. Because of this hoists physical characteristics, and South African mining rules favouring it in one respect, they are used mostly for the deep shaft mineral hoisting. The drum diameters are smaller than that of an equivalent conventional hoist, so one advantage is that they are more easily taken underground for sub-shaft installations. A Blair hoist is essentially a conventional hoist with wider drums, each drum having a centre flange that enables it to coil two ropes attached to a skip via two headsheaves. The skip connection has a balance wheel, similar to a large multi-groove V-belt sheave, to allow moderate rope length changes during winding. The sheaves can raise or lower to equalize rope tensions. The Blair hoists physical advantage is that the drum diameter can be smaller than usual and, with two ropes to handle the load, each rope can be much smaller. The government mining regulations permit a 5 % lower safety factor at the sheave for mineral hoisting with Blair hoists. This came about from a demonstration by the% permits the Blair hoists to go a little deeper than the other do. On the other hand, the mining regulations require a detaching hook above the cage for man hoisting. The balance wheel does not suit detaching hooks, so a rope-cutting device was 4invented to cut the ropes off for a severe overwind. This was tested successfully but the Blair is not used for man winding on a regular basis. The B.M.R. hoist has been built in three general styles similar to conventional hoists. The three styles are (Fig. 3 and 4): The gearless B.M.R. hoist at East Dreifontein looks similar to an in-line hoist except that the drums are joined mechanically and they are a little out of line with each other. This is because each drum directly faces its own sheaves for the best fleet angle. The two hoist motors are fed via thyristor rectifier/inverter units from a common 6.6-KV busbar. The motors are thus coupled electrically so that the skips in the shaft run in balance, similar to a conventional double-drum hoist. Each motor alternates its action as a DC generator or DC motor, either feeding in or taking out energy from the system. The gearless Blair can be recognized by the offset drums and the four brake units. A second brake is always a requirement, each drum must have two brakes, because the two drums have no mechanical connection to each other. Most recent large B.M.R. hoists are 4.27 or 4.57 m in diameter, with 44.5 47.6 mm ropes 1. In arriving at a drum size the following parameters have been used: (1) The rope to be coiled in four layers, 5(2)The rope tread pressure at the maximum static tension to be less than 3,2 MPa, (3) The drum to rope diameter ratio (D/d) to be greater than 127 to allow for a rope speed of 20 m/s. With the above and a need to limit the axial length of the drums, a rope compartment of 8,5 m diameter by 2,8 m wide, was chosen. The use of 5 layers of coiled rope could reduce the rope compartment width to 2,15 m but this option has been discarded at this stage because of possible detrimental effects on the rope life. One problem often associated with twin rope drum hoists is the rope fleeting angle. The axial length of the twin rope compartment drums requires wide centres for the headgear sheaves and conveyances in the shaft. To limit the diameter of the shaft, the arrangement illustrated in Fig. 4 has been developed and used on a hoist still to be installed. Here, an universal coupling or Hookes Joint has been placed between the two drums to allow the drums to be inclined towards the shaft center and so alleviate rope fleeting angle problem, even with sheave wheels at closer centres 11. The rope safety factor The graphs in Fig. 5 illustrate the endload advantage with reducing static rope safety factors. While serving their purpose very well over the years, the static safety factor itself must now be questioned. Static safety factors, while specifically relating to the static load in the rope were in fact established to take account of: a. Dynamic rope loads applied during the normal winding cycle, particularly during loading, pull-away, acceleration, retardation and stopping, b. Dynamic rope loads during emergency braking, c. Rope deterioration in service particularly where this is of an unexpected or unforeseen nature. If peak loads on the rope can be reduced so that the peak remains equal to or less than that experienced by the rope when using current hoisting practices with normal static rope safety factor, the use of a reduced static rope safety factor can be justified. The true rope safety factor is not reduced at all. This is particularly of importance during emergency braking which normally imposes the highest dynamic load on the rope. Generally, the dynamic loads imposed during the skip loading, cyclic speed changes and tipping will be lower than for emergency braking but their reduction will of course improve the rope life at the reduced static rope safety factor. The means, justification and safeguards associated with a reduced 6static safety factor are discussed in 4,7,9,12. Based on the static rope safety factor of 4, the rope endload of 12843 kg per rope can be achieved. With twin ropes, this amounts to an endload of 25686 kg. With a conveyance based on 40 % of payload of 18347 kg with a conveyance of 7339 kg. There are hoisting ropes of steel wires strength up to Rm = 2300 MPa (Rm up to 2600 MPa 6 is foreseen) used in deep shafts. There are also uniform strength hoisting ropes projected 2,8. Conveyances The winding machines made from a light alloy are used in hoisting installations in deep shafts. The skip factor (S) has been defined as the ratio of empty mass of the skip (including ancillary equipment such as rope attachments, guide rollers, etc) to the payload mass. If the rope end load is kept constant, a lower skip factor implies a larger payload in other words, a more efficient skip from a functional point of view. However, the higher the payload for the same rope end load, the larger the out-of-balance load implying a more winder power going hand in hand with the higher hoisting capacity. If, on the other hand, the payload is fixed, a lower skip factor implies a lower end load and a smaller rope-breaking load requirement. Under these conditions, an out-of-balance load attributable to the payload would remain the same, but that due to the rope would reduce slightly. The sensitivity of depth of wind and hoisting capacity to skip the factor is illustrated in Fig. 6 and 7. A reduction of skip factor from 0,5 to 0,4 results in a depth gain of about 40 m for Blair winders and 50 m for single-rope winders. The increase of hoisting capacity for a reduction of skip factor by about 0,1 is about 10 %. Typical values for the “skip factor” are about 0,6 for skips and about 0,75 for cages for men and material hoisting. Reducing skip factors to say about 0,5 is a tough design brief and the trade-offs between lightweight skips and maintainability and reliability soon become evident in service. The weight can be readily reduced by omitting (or reducing in thickness) skip liner plates but this could reduce skip life by wear of structural plate leading to the high maintenance cost or more frequent maintenance to replace thinner liner plates. Similarly, if the structural mass is saved by reducing section sizes or changing the material from steel to aluminium for example, the structural reliability is generally reduced and the fatigue cracking becomes more efficient. Some success has been achieved in operating large capacity all aluminium skips with 7low skip factors but the capital cost is high and a very real hoisting capacity constrain must exist before the additional cost is warranted. It would appear that the depth and hoisting capacity improvements are better made by reducing the rope factor of safety and increasing the winding speed. The philosophy of the skip design should be to provide robust skips with reasonable skip factors in the range of 0,5 to 0,6 that can be hoisted safely and reliably at high speeds and that are tolerant to the shaft guide misalignment. It should be noted that some unconventional skips have been proposed (but not yet built and tested) that could offer skip factors as low as 0.35.Conclusions The first installation of Blaire hoists took place in 1958. From that time we can observe a continuous development of this double-rope, double-drum hoists. Currently, they are used up to the depth of 3 150 m (man/material hoist at the Moab Khotsong Mine, to hoist 13 500 kg in a single lift, at 19,2 m/sec, using 2 x 7400 kW AC cyclo-convertor fed induction motors). The Blair Multi-Rope system can be use either during shaft sinking or during exploitation. The depth range for them is 715 to 3150 m and the maximum skip load is 20 tons. In South Africa in deep shafts single lift systems are preferred. References 1 BAKER. T.J.: New South African Drum Hoisting Plants. CIM Bulletin, No 752, December 1994, p. 86-96. 2 CARBOGNO, A.: Winding Ropes of Uniform Strength. 1st International Conference 8LOADO 2001. Logistics and Transport. Hotel Permon, High Tatras, June 6th 8th 2001 p.214-217. 3 GREENWAY, M.E.: An Engineering Evaluation of the Limits to Hoisting from Great Depth. Int. Deep Mining Conference: Technical Challenges in Deep Level Mining, Johannesburg, SAIMM, 1990 p.449-481. 4 HECKER, G.F.K.: The Safety of Hoisting Ropes in Deep Mine Shafts. International Deep Mining Conference: Technical Challenges in Deep Level Mining. Johannesburg, SAIMM, 1990 p. 831-838. 5 HILL, F.G, MUDD J,B: Deep Level Mining in South African Gold Mines. 5th International mining Congress 1967, Moscow, p. 1 20. 6 LANE, N.M: Constraints on Deep-level Sinking an Engineering Point of View. The Certificated Engineer, vol. 62, No6, December 1989/January 1991 p. 3-9. 7 LAUBSCHER, P.S.: Rope Safety Factors for Drum Winders Implications of the Proposed Amendments to the Regulations. Gencor Group, 1995 Shaft Safety Workshop. Midrand, Johannesburg, November 1995, paper No 5 p.1-11. 8 MAC DONALD, D.H., PIENAAR, F.C.: State of the Art and Future Developments of Steel Wire Rope in Sinking and Permanent Winding Operations. Gencor Group, Shaft Safety Workshop Magaliesberg, 1994, paper No 13, p. 1-21. 9 MCKENZIE, I.D.: Steel Wire Hoisting Ropes for Deep Shafts. International Deep Mining Conference: Technical Challenges in Deep Level Mining. Johannesburg, SAIMM, 1990 p. 839-844. 10 SPARG, E.N.: Development of SA- Designed and Manufactured Mine Winders. The South African Mechanical Engineer vol.35, No 10, October 1985 p. 418-423. 11 SPARG E,N.: Developments in Hoist Design Technology Applied to a 4000 m Deep Shaft. Mining Technology, No 886, June 1995, p. 179-184. 12 SYKES, D.G., WIDLAKE, A.C.: Reducing Rope Factors of Safety for Winding in Deep Levels Shafts. International Deep Mining Conference. Technical Challenges in Deep Level Mining. Johannesburg, SAIMM, 1990 p. 819-829. 910中文译文21世纪前半叶矿井挖掘机在深井中的应用关键词: 深井，矿井挖掘机，布莱尔挖掘机，钢丝绳安全要素，滚筒尺寸，骤变要素介绍矿物沉淀物在越来越深的水平上被开采。关于这方面，像“深水平面”和“深井”的定义变得越来越流行了。这些定义与有关特殊规则方面的深度有关，涉及到挖掘操纵、开采、岩石压力控制、内层建造、通风，地下和垂直的运输, 劳动组织和经济学应用。“深水平面”已经被指出是一种非常相对的定义，这个定义应当只能用于采矿或煤领域有关特殊的水-地质学, 采矿和技术条件方面的参考。它也应当用于严格定义已经公认的有关“深水平面”或“深井”领域的定义。可以举例来说 :（1）采矿工程技术,（2）开采操纵技术,（3）通风 (降低温度).明显的是，从一方面得到的“深水平面”定义,在其他领域并不意味着“深水平面” 。 根据第5段提到的“深井”，我们可以设想每一个矿井：（1）深度超过2300米深或者（2）矿石沉积物的温度超过38摄氏度。广为人知的是大部分深井在南非。通常，它们是金矿或者钻石矿井。人们都知道像黄金方面矿石的经济沉淀物存在于南非一些深达5000米的深井领域。然而，在一些区域中，存在暗礁的深度和结构要素，先前在垂直的深井中使用的到达深度暗礁的方法在经济上不可取。因此，当地的采矿业正在积极地研究在不久的将来能够用于深度达到3500米或者未来深度在5000米左右的矿井中的单一挖掘技术。相对于当今深度达2500米的矿井中的挖掘技术，它的一些创新在将来会有很大的意义。在深井中最重要的事件是垂直运输以及矿井挖掘技术在井中的应用。参考文献的1至12篇可以得出这样的结论:布莱尔多绳挖掘机在南非的深井应用中是首选的。从经济学的观点看, 最重要的要素是:（1）挖掘绳索的构造和参数(主要是安全要素)；（2）矿井挖掘绞车的承载能力。这篇见闻广博性质的文章简略的介绍了上述基于参考文献1至12篇所反映的问题。尤其, M.E. Greenway写的文献【3】非常有趣。从被应用于深井中的双运输系统，接近垂直的以及单一的井中挖掘系统，第二种系统是目前首选的。参见插图1/参考文献11【6】。挖掘装置：挖掘机（挖掘深度达2100米），单独的和双滚筒挖掘机（第一流的和布莱尔形式的双滚筒挖掘机）广泛应用于南非地区。1 Carbogno Alfred Ing 博士, 来自波兰格利维策市西里西亚技术大学，采矿机械化学会，Akademicka 2，PL 44-101 Gliwice, (他于2002年8月5日修订了先前被公认为是标准的版本)。滚筒挖掘机：滚筒挖掘机被广泛应用于南非或许全世界。三种类型的挖掘机属于这样的类型：（1）单一滚筒挖掘机,（2）双鼓挖掘机,（3）布莱尔多绳绕线机 (BMR)。双滚筒挖掘机：双滚筒应用于单井，钢丝绳以相对的方向缠绕在它的上面，以保持运输工具的平衡。单一或者双滚筒附着于井，使得运输工具能够在相对于井的位置上变换以及从不等高的水平面平稳的挖掘。布莱尔多绳系统 (BMR)在1957年，布莱尔罗伯特引进了一种挖掘系统，这种系统可以将滚筒的优势扩大到能够缠绕两根或多根钢丝绳。这种双绳系统发展成为二合一的滚筒，每一部分一根绳以及两根绳附着在单一的运输工具上。他也开发了一种张紧12滑轮装置，把它附着在运输工具上。矿山部门说：倘若任何一根绳的承载能力要素不能降至法定要素9以下，将允许挖掘机械的法定安全要素从4275更改为45。这样一种补偿的必要性使得处于两根绳之间的载荷能够平衡分配。因为滑轮的补偿作用有限，布莱尔同样发明了一种装置来监测滚筒的误差，因为这样可以使得钢丝绳能够以不同的速度移动以及干预两根绳能够按他们的实际承载能力分配。图2描述了双滚筒的深度有效载荷的特性，布莱尔和Koepe挖掘机。布莱尔挖掘机几乎专一性的应用于南非地区，或许由于这些机器是在那儿发明的，尤其是应用于深井。在英国有一套设备。因为这种挖掘机的物理性能好，以及南非地区的矿井规程在某一方面特别亲赖于它，他们主要被应用于深井挖掘系统。这种滚筒的直径比普通相当规格的挖掘机小，因此一方面的优点是它们更加便于在井下安装。布莱尔挖掘机本质上是带有宽鼓的常规挖掘机，每个滚筒有一个中心凸轮，以使得两根绳子能够缠绕在上面，用来急速改变两个主导轮。急变系统拥有一个平衡轮, 类似于大的多凹槽形的V带滑轮, 以允许在挖掘过程中绳索长度的适度变化。滑轮能升起或者降低以使得钢丝绳的张紧力相等。布莱尔挖掘机的物理性能优势表现在滚筒的直径比普通的小，以及两根绳子同时承载载荷，使得每根绳子能够变得更加小些。政府部门的采矿规则允许使用布莱尔挖掘机的矿井在滑轮安全要素方面低于正常5。这从发明家罗勃特布莱尔的演示可以看出, 一根严格符合要求的钢丝绳,以额定速度运转，由剩余的钢丝绳承担负载。这5%的安全要素允许布莱尔挖掘机比其他挖掘机稍微深入一些。 另一方面,采矿规则要求为方便人们的升降，在罐笼的上方必须安装有可分离的吊钩。平衡轮不适合用于分离吊钩，因此，发明了一种可以切断绳索的装置用来切断旋得很紧的绳索。这种装置顺利通过试验，但是布莱尔挖掘机不是用于人类规范准则的挖掘机。布莱尔挖掘机已经被应用于三种类似于传统挖掘机的普通风格的类型中。这三种风格可见图3和图4。13在Dreifontein东部的无传动装置的B.M.R.挖掘机除滚筒连接以及它们相互不在同一中心外，从外表上看似同轴挖掘机。这是因为每个滚筒直接地面对自己的滑槽轮而获得最佳的深浅角度。两个挖掘机的马达通过6.6千伏的半导体闸流管整流换流器/反用换流器来反馈。马达与电相连接以便轴中的急变能够保持平衡，类似于传统的双滚筒挖掘机。每台马达交替变换它们的作用相当于直流发电机或者直流电动机任意的从系统中输入或者输出能量。无传动装置的布莱尔挖掘机能够被偏移滚筒和四种刹车装置所检验。第二种刹车永远是必要的，每个滚筒必须有两个刹车，因为两个滚筒之间没有机械连接。大部分最新的布莱尔挖掘机直径达到4.27或者4.57米，附带有直径达44.5至47.6毫米的钢丝绳。在达到滚筒的尺寸方面，以下的参数已经被采用:（1）钢丝绳被缠绕成四层，（2）钢丝绳的最大静态压力要小于32兆帕，（3）滚筒与钢丝绳的直径比（大径比小径）要大于12，以保证钢丝绳的速度达到20米/秒。综上所述为限制滚筒的轴的长度的需要，钢丝绳减速箱的尺寸选择为直径85米、宽28米。 5层缠绕的钢丝绳的利用可以使钢丝绳间隔间的宽度减少到215米，但是这种想法在此阶段已经被放弃，是因为它们可能对钢丝绳的寿命有负面影响。14经常与双绳滚筒挖掘机有关的一个问题是钢丝绳的短暂角度，双绳间隔间滚筒的轴长为了挖掘机能够在矿井中顺利的运输，需要宽敞的中心区。为了限制井的直径，在图4中安排的插图直到挖掘机被安装才被证实是正确的。这里，通用的或者Hooke的结合点已经在双滚筒之间安置，这是为了允许滚筒在矿井中心被连接以及能够减小钢丝绳的角度问题，以及槽轮在靠近的中心问题。钢丝绳的安全要素：在图5中的图表举例说明了钢丝绳在减少静态安全要素方面的负载优势。当数年以来很好的满足它们的目的，静态安全要素现在本身一定会被质疑的。静态安全要素，虽然在钢丝绳上与静态负载有明确的关联，事实上已经有了明确的考虑：a、动态的绳索负载应用于正常的缠绕循环周期中，尤其在加载、离开、加速、延迟以及停止，b、动态绳索负载在紧急制动中，c、工作期间的绳索变化尤其处于以外的或者无法预料的状态。如果钢丝绳的最大负载能够减少以便最大负载残余应力能够平担或者少于曾经承受过的负载，当使用的当前的挖掘实际能力以及普通的静态绳索安全要素，静态绳索安全要素降低的利用被证实是正确的。真正的绳索安全要素实质上并没有减少。这在钢丝绳处于最大动态负载的紧急制动中尤其重要。通常，在负载急变瞬间的动态加载，循环的速度变化将会紧急制动的情况，但是它们的减少一定会在减少的静态绳索安全要素方面改善钢丝绳的寿命。那些与降低的静态安全要素相关的合理的以及安全的手段在参考书4，7，9，12中有相关的讨论。基于第四篇文献中涉及的静态绳索安全要素，每一根钢丝绳所能承受的最大负载为12843千克。对于双绳来说，最大负载量达到25686千克。基于18347千克的运输量的40的有效载荷为7339千克。在深井中挖掘钢丝绳的力量最大可以达到2300兆帕（在第六篇参考文献中所估计的可以达到2600兆帕）。在第2，8篇参考文献中提到的挖掘机钢丝绳被设计成统一的额定载荷。运输缠绕机器由闪光合金制成广泛使用于深井挖掘设备中。急变要素作为空载对有效载荷的比例已经被详细的论述（包括辅助设备，例如钢丝绳附加装置、引导滚筒等等）。如果钢丝绳的最大载荷保持不变，一种低级的急变要素暗示着有更大的有效载荷，换句话说，是来自于功能观点的更有效率的急变特征。然而，同一钢丝绳的有效最大载荷越高，来自平衡的载荷越大，意味着与挖掘高能量相关的缠绕能量越来越高。另一方面，如果有效载荷被确定，更低的急变要素意味着更低的最大负载以及更小的绳索15制动加载设备。在这些条件下，来自于平衡外的负载虽然仍然归于有效载荷，但是应归于绳索的少量降低。在图6、7中描述了缠绕和挖掘机容量的深度灵敏性。急变要素从0.5降低到0.4，导致布莱尔挖掘机深度增加大约40米，单绳挖掘机增加大约50米。急变要素降低了0.1使得挖掘机容量大约增加了10。急变要素的典型价值体现在人和材料挖掘运输方面，急变方面为0.6，罐笼方面为0.75。在工作中轻量级以及可维护性和可靠性迅速变得明显之间，急变要素的降低被认为与0.5有关，其实是一种很难的规划设计。重量可以很容易的通过省略(或者在厚度方面减少)急变衬垫金属板 ，但是这种方法可能会通过结构金属板的磨损使得急变寿命减少，导致需要很高的维护费用或者更加频繁的维护来替换更加薄的结构金属板。同样的举个例子，如果结构块通过减少结构尺寸或者将钢材料更换为铝材料 ，结构可靠性一般会降低，疲劳裂纹会变得更加明显。在运行大容量含有低急变要素的全铝急变方面曾经获得一些成功，但是在被批准附加经费之前，一定存在很高的容量费用，以及真正的加载挖掘容量。看来通过降低钢丝绳的安全要素以及增加缠绕的速度，可以使得挖掘的容量和深度得到改进。介于0.5至0.6之间的合理急变要素的设计哲理，可以提供更好的急变，能够在高速下未定位准确的井中使得挖掘更加安全和可靠。一些非传统的能够低至0.35的急变要素已有历史记载（但是没有被
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