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(二) 某建筑工程，建筑面积108000m2，现浇剪力墙结构，地下3层，地上50层。基础埋深14.4mm，底板厚3m，底板混凝土强度等级为C35。底板钢筋施工时，板厚1.5m处的HRB335级直径16mm钢筋，施工单位征得监理单位和建设单位同意后，用HPB235钢筋直径10mm的钢筋进行代换。施工单位选定了某商品混凝土搅拌站，由该项间为其制定了底板混凝土施工方案。该方案采用溜槽施工，分两层浇筑，每层厚度1.5m。底板混凝土浇筑时，当地最高大气温度38℃，混凝土最高入模温度40℃。浇筑完成12h后采用覆盖一层塑料膜一层保温岩棉养护7d。测温记录显示：混凝土内部最高温度75℃，其表面最高温度45℃。监理工程师检查发现底板表面混凝土有裂缝，经钻芯取样检查，取样样品均有贯通裂缝。问题该基础底板钢筋代换是否合理说明理由。

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(二) 某建筑工程，建筑面积108000m2，现浇剪力墙结构，地下3层，地上50层。基础埋深14.4mm，底板厚3m，底板混凝土强度等级为C35。底板钢筋施工时，板厚1.5m处的HRB335级直径16mm钢筋，施工单位征得监理单位和建设单位同意后，用HPB235钢筋直径10mm的钢筋进行代换。施工单位选定了某商品混凝土搅拌站，由该项间为其制定了底板混凝土施工方案。该方案采用溜槽施工，分两层浇筑，每层厚度1.5m。底板混凝土浇筑时，当地最高大气温度38℃，混凝土最高入模温度40℃。浇筑完成12h后采用覆盖一层塑料膜一层保温岩棉养护7d。测温记录显示：混凝土内部最高温度75℃，其表面最高温度45℃。监理工程师检查发现底板表面混凝土有裂缝，经钻芯取样检查，取样样品均有贯通裂缝。问题本工程基础底板产生裂缝的主要原因是什么

Agriculture is undoubtedly the most important sector in the economies of most non-oil exporting African countries. It (62) about 30% of Africa’s GDP and contributes (63) 50% of the total export value, (64) 70% of the continent’s population depending on the sector for their (65) . Production is subsistence in nature with a high (66) on the rain. The debate on climate change and its impacts on agriculture is (67) very crucial to the very survival of the continent and its people. The continent is particularly (68) to climate change because it includes some of the world’s poorest nations. The climate in Africa is (69) tropical in nature, which is broadly (70) into three main climatic zones: (71) equatorial, dry, and temperate(温带). Within these zones, altitude and other localized (72) also produce distinctive regional climates. Climate change, (73) indicated by prolonged drought is one of the most serious climatic (74) affecting the agricultural sector of the continent. As most of the agriculture activities in African countries hinges on rain fed, any adverse changes in the climate would likely have a (75) effect on the sector in the region. (76) changes in the climate may affect the whole continent, its (77) may vary across the continent. In northeast Africa, more intense dry periods and shorter wet seasons are expected to affect even huge river systems such as the Blue Nile, leading to serious water shortages and (78) consequences to the agriculture and forestry sectors throughout the region. East and Central Africa will also see its agricultural (79) decline. Coastal areas may also be affected by rising sea levels and intrusion of salt water into inland freshwater resources. The staple food for the region, maize, is particularly susceptible to drought. Wetlands of international importance and wildlife are also under threat from (80) in Southern Africa. Climate change, therefore, is expected to worsen the food supply, (81) , exacerbate the widespread poverty in the region.

A. production
B. technology
C. capacity
D. ability

It is essential in modern society that ______(具备应对突发情况的能力).

(四) 某施工总承包单位承担一项建筑基坑工程的施工，基坑开挖深度12m，基坑南侧距坑边6m处有一栋6层住宅楼。基坑土质状况从地面向下依次为：杂填土0～2m，粉质土2～5m，砂质土5～10m，黏性土10～12m，砂质土12～18m。上层滞水水位在地表以下5m(渗透系数为0.5m/d)，地表下18m以内无承压水。基坑支护设计采用灌注桩加锚杆。施工前，建设单位为节约投资，指示更改设计，除南侧外其余三面均采用土钉墙支护，垂直开挖。基坑在开挖过程中北侧支护出现较大变形，但一直未被发现，最终导致北侧支护部分坍塌。事故调查中发现： (1)施工总承包单位对本工程作了重大危险源分析，确认南侧毗邻建筑物、临边防护、上下通道的安全为重大危险源，并制订了相应的措施，但未审批。 (2)施工总承包单位有健全的安全制度文件。 (3)施工过程中无任何安全检查记录、交底记录及培训教育记录等其他记录资料。问题施工总承包单位还应采取哪些有效措施才能避免类似基坑支护坍塌