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如图所示重力式挡土墙，墙背直立、光滑、填土面水平，墙高6m。填土资料如下：①填土面作用有连续均匀分布荷载q=10kPa；②填土由两层土组成，第Ⅰ层土为黏性土，γ1=18kN/m3，ck=10kPa，=20°；第Ⅱ层土为砂土，=30°，γ=18kN/m3；③填土中有地下水，地下水位在砂土表面，砂土饱和重度γsat=20kN/m3。计算作用在挡土墙上的主动土压力。 只考虑③，填土是均匀的砂土，有地下水，无均布荷载，作用在挡土墙上的主动土压力最接近（）。
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某建筑场地，地质资料如下：地表下第一层土为杂填土，厚2m，重度 16.0kN/m3；第二层土，粉土厚4.5m，黏粒含量ρc=14%，饱和重度19.6kN/m3，Es=7.20MPa，试验测得地基承载力特征值fak=165kPa；其下为较厚的淤泥质黏土：重度19.0kN/m3，Es=2.40MPa，地基承载力特征值fak=85kPa。地下水位在地面下2.0m处，可取基底埋深d=2.0m。 基础为框架内柱下矩形台阶基础，矩形柱500mm×500mm，基础底面尺寸4.5m×4.5m，基础高度900mm，100厚C10混凝土垫层。上部结构传至基础顶面轴心力设计值F=3200kN，计算得基础底面反力P=198kPa，底面平均附加压力Po=166kPa。矩形基础采用C25混凝土，基础底板钢筋HRB335。计算： 验算软弱下卧层时，淤泥质土层的地基压力扩散角应为( )。
某钢筋混凝土框架柱基础，柱截面500mm×500mm。基础埋深2.0m，经修正后的地基持力层承载力特征值fa=230kPa。基础埋深范围内土的加权平均重度γm= 18.0kN/m3。基础混凝土为C25，混凝土抗拉强度设计值ft=1.27N/mm2；钢筋采用HPB235，fv=210N/mm2。基础下做100厚C10混凝土垫层，基础台阶拟采用阶梯形，每阶高度300，基础总高度900mm。上部结构荷载效应的标准组合：Fy=2780kN。 如果基础底面尺寸采用4m×4m，则可以计算出基底净反力为（）。
如图所示某柱下独立基础，基础底面尺寸3.0m×2.5m，上部结构传至基础的荷载效应：轴向荷载Fk=1650kN，基础埋深1.5m(不考虑相邻基础荷载的影响)。 基础底面附加压力最接近于（）。
The immune system is equal in complexity to the combined intricacies of the brain and nervous system. The success of the immune system in defending the body relies on a dynamic regulatory communications network consisting of millions and millions of cells. Organized into sets and subsets, these cells pass information back and forth like clouds of bees swarming around a hive. The result is a sensitive system of checks and balances that produces an immune response that is prompt, appropriate, effective and self-limiting. At the heart of the immune system is the ability to distinguish between self and non-self. When immune defenders encounter cells or organisms carrying foreign or non-self molecules, the immune troops move quickly to eliminate the invaders. Virtually every body cell carries distinctive molecules that identify it as self. The body’’s immune defenses do not normally attack tissues that carry a self marker. Rather, immune cells and other body cells coexist peaceably in a state known as self-tolerance. When a normally functioning immune system attacks a non-self molecule, the system has the ability to remember the specifics of the foreign body. Upon subsequent encounters with the same species of molecules, the immune system reacts accordingly. With the possible exception of antibodies passed during lactation ( 哺乳期 ), this so-called immune system memory is not inherited. Despite the occurrence of a virus in your family, your immune system must learn from experience with the many millions of distinctive non-self molecules in the sea of microbes in which we live. Learning necessitates producing the appropriate molecules and cells to match up with and counteract each non-self invader. Any substance capable of stimulating an immune response is called an antigen. Tissues or cells from another individual (except an identical twin, whose cells carry identical self-markers ) act as antigens; because the immune system recognizes transplanted tissues as foreign, it rejects them. The body will even reject nourishing proteins unless they are first broken down by the digestive system into their primary, non-antigenic building blocks. An antigen announces its foreignness by means of intricate and characteristic shapes called epitopes( 抗原决定基), which stick out from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitopes on their surface, some may even carry several hundred. Some epitopes will be more effective than others at stimulating an immune response. Only in abnormal situations does the immune system wrongly identify self as non-self and execute a misdirected immune attack. The result can be so-called autoimmune disease. The painful side effects of these diseases are caused by a person’’s immune system actually attacking itself The remembering power of a person’’s immune system is
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