最新電大工程地質(zhì)形成性考核冊(cè)作業(yè)參考答案小抄-文庫(kù)吧
2025-05-14 01:57 本頁(yè)面
【正文】 選擇洞軸線位置時(shí)應(yīng)考慮哪些因素？ 答：選擇洞軸線位置應(yīng)考慮（ 1）地形：應(yīng)注意利用地形、方便施工。（ 2）地層與巖性條件：地層與巖性條件的好壞直接影響洞室的穩(wěn)定性。（ 3）地質(zhì)構(gòu)造條件：應(yīng)考慮在大塊而完整巖體中布置軸線；應(yīng)注意分析洞軸線與巖層產(chǎn)狀、褶皺地層的走向的關(guān)系。（ 4）水文地質(zhì)條件：對(duì)隧洞沿線地下水分析其埋藏運(yùn)動(dòng)條件、類型及物理化學(xué)特性等情況。 2． 保障圍巖穩(wěn)定性的兩種途徑是什么 ？ 答： 保障圍巖穩(wěn) 定性的途徑有二：一是保護(hù)圍巖原有穩(wěn)定性，使之不至于降低；二是提高巖體整體強(qiáng)度，使其穩(wěn)定性有所增高。前者主要是采用合理的施工和支護(hù)襯砌方案，后者主要是加固圍巖 。 3． 衡量膨脹土特性的指標(biāo)有哪些？各自的物理意義是什么？ 膨脹土工程特性指標(biāo)主要有四個(gè)：自由膨脹率 δef 、膨脹率 δep 、收縮系數(shù) λs和膨脹力 Pe 物理意義 ： 自由膨脹率是指人工制備的土樣，完全烘干后，在水中增大的體積與其原有體積之比； 膨脹率是指原狀土樣在一定壓力下浸水膨脹穩(wěn)定后所增加的高度與原始高度之比； 收縮系數(shù)是指原狀土樣在直線收縮階段，含水量 減少 1%時(shí)的豎向收縮變形的線縮率； 膨脹力是指原狀土樣在體積不變時(shí)，由于浸水膨脹而產(chǎn)生的最大內(nèi)應(yīng)力，可由壓力與膨脹率的關(guān)系曲線來確定，它等于曲線上當(dāng)為零時(shí)所對(duì)應(yīng)的壓力。 4． 工程地質(zhì)勘察的任務(wù)是什么？ 答：見教材 P150 其主要任務(wù)是通過……設(shè)計(jì)方案。 5． 巖土工程分析評(píng)價(jià)的主要包括的內(nèi)容有哪些？ 答：見教材 P164 四．論述題 1． 分析巖體破壞的機(jī)理及漸進(jìn)破壞。 答：見教材 P124 請(qǐng)您刪除一下內(nèi)容， O(∩ _∩ )O 謝謝?。。?2021 年中央電大期末復(fù)習(xí)考試小抄大全，電大期末考試必備小抄，電大考試必過小抄Acetylcholine is a neurotransmitter released from nerve endings (terminals) in both the peripheral and the central nervous systems. It is synthesized within the nerve terminal from choline, taken up from the tissue fluid into the nerve ending by a specialized transport mechanism. The enzyme necessary for this synthesis is formed in the nerve cell body and passes down the axon to its end, carried in the axoplasmic flow, the slow movement of intracellular substance (cytoplasm). Acetylcholine is stored in the nerve terminal, sequestered in small vesicles awaiting release. When a nerve action potential reaches and invades the nerve terminal, a shower of acetylcholine vesicles is released into the junction (synapse) between the nerve terminal and the ?effector‘ cell which the nerve activates. This may be another nerve cell or a muscle or gland cell. Thus electrical signals are converted to chemical signals, allowing messages to be passed between nerve cells or between nerve cells and nonnerve cells. This process is termed ?chemical neurotransmission‘ and was first demonstrated, for nerves to the heart, by the German pharmacologist Loewi in 1921. Chemical transmission involving acetylcholine is known as ?cholinergic‘. Acetylcholine acts as a transmitter between motor nerves and the fibres of skeletal muscle at all neuromuscular junctions. At this type of synapse, the nerve terminal is closely apposed to the cell membrane of a muscle fibre at the socalled motor end plate. On release, acetylcholine acts almost instantly, to cause a sequence of chemical and physical events (starting with depolarization of the motor endplate) which cause contraction of the muscle fibre. This is exactly what is required for voluntary muscles in which a rapid response to a mand is required. The action of acetylcholine is terminated rapidly, in around 10 milliseconds。 an enzyme (cholinesterase) breaks the transmitter down into choline and an acetate ion. The choline is then available for reuptake into the nerve terminal. These same principles apply to cholinergic transmission at sites other than neuromuscular junctions, although the structure of the synapses differs. In the autonomic nervous system these include nervetonerve synapses at the relay stations (ganglia) in both the sympathetic and the parasympathetic divisions, and the endings of parasympathetic nerve fibres on nonvoluntary (smooth) muscle, the heart, and glandular cells。 in response to activation of this nerve supply, smooth muscle contracts (notably in the gut), the frequency of heart beat is slowed, and glands secrete. Acetylcholine is also an important transmitter at many sites in the brain at nervetonerve synapses. To understand how acetylcholine brings about a variety of effects in different cells it is necessary to understand membrane receptors. In postsynaptic membranes (those of the cells on which the nerve fibres terminate) there are many different sorts of receptors and some are receptors for acetylcholine. These are protein molecules that react specifically with acetylcholine in a reversible fashion. It is the plex of receptor bined
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